enhancement of the interlayer interaction between...

Research ArticleEnhancement of the Interlayer Interaction between Polystyreneand Polyvinyl Alcohol by Ozone Treatment

Lin Su Jie Li Jing Li Qiaomei Chu Bo Li and Yiyang Liu

Research Center of Laser Fusion China Academy of Engineering Physics Mianyang 621900 China

Correspondence should be addressed to Yiyang Liu cqmhb821163com

Received 28 October 2018 Accepted 21 April 2019 Published 18 June 2019

Academic Editor Katja Loos

Copyright copy 2019 Lin Su et al This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The ozonization modification of polystyrene (PS) was conducted in acidic condition to enhance the interfacial interaction betweenPS and polyvinyl alcohol (PVA) Infrared spectra results revealed that the carbonyl and hydroxyl groups were successfullyintroduced to the PS film by ozonization The hydrophobic PS was turned to be hydrophilic to some extent by contact angleexperiment which led to the enhancement of interfacial adhesion between PS and PVA In addition the adsorption of PS to PVAwas also improved Nano indenter measurement indicated the interfacial interaction between PS film and PVA film was obviouslyenhanced by 40 after ozonization at room temperature for 2 h in acidic condition which will benefit for fabricating laser inertialconfinement fusion container

1 Introduction

Carbon and hydrogen element with low atomic number isoften served as the hollow microspheres material of thecontainer for the laser inertial confinement fusion (ICF)experiment [1ndash5] Polystyrene (PS) is an ideal candidatematerial because of the easy fabricating process of its micro-spheres However the hydrogen barrier property of PS isvery poor [6] Therefore a barrier layer should be addedon the surface of PS to prevent the leakage of fuel gas fromthemicrospheres Polyacrylonitrile (PAN) Polyvinyl Alcohol(PVA) and carboxymethyl cellulose have a good barrier effecton hydrogen Among these polymers only PVA is easy toformmicrospheres and has been investigated extensively Thediameter of PS-PVA dual hollow microspheres should rangefrom 200120583m to 500120583m [7]

The shear force of outer sphere is the main factor whichcan affect the deformation of the microspheres during thepreparation of the dual hollow microspheres The surfacetension of droplet is the driving force tomaintain its sphericalshape [8ndash11] The droplets will divide into several smallerdroplets if the deformation ratio is bigger than 05 Howeverthe exfoliation of PVA shell from PS sphere will occur whenthe deformation ratio of outer PVA shell exceed a criticalvalue Two reasons will lead to this unexpected phenomenon

one is the great modulus differences and the other is theweak interaction between PVA and PS Consequently the PSspheres will be dissolved by the outer oil phase [12]

The Cox [13] equation for the deformation of liquid dripcan be simplified as follows

119863 = 12 ∙ (1 + 316120582 + 16) ∙ ( 1radic(1912058240)2 + 11198702) (1)

where119870 = 120578119898 ∙120574 119889120592 120578119898 is the viscosity of medium and∙120574

is the shear rate and 120592 is the surface tension Here 120582 = 120578119889120578119898120578119889 and d are the viscosity and diameter of liquid dropletsrespectively

According to (1) the deformation (D) of liquid dropletswill increase with its diameter which will lead to the severeexfoliation between PVA shell and PS sphere for the largehollow sphere Therefore it is very difficult to fabricatethe large hollow microspheres via the microemulsificationtechnology when the diameter exceeds 500120583m [12]

However the development of ICF experiment requiresthe hollow microspheres with larger diameter In this paperthe ozonization technique is introduced to solve this prob-lem The ozonization technique is often used in polymer

HindawiAdvances in Polymer TechnologyVolume 2019 Article ID 7831619 8 pageshttpsdoiorg10115520197831619

2 Advances in Polymer Technology

surface modification for its easy procedure and low cost [14ndash20] Once polymer is exposed in ozone atmosphere somecarbonyl groups and carboxyl groups will appear on thepolymer chains In addition some peroxide groups will alsogenerate The peroxide group will change to hydroxyl groupafter ultraviolet illumination or heated Consequently thesurface of polymer will become hydrophilic to some extent[19 21ndash23] Then the interfacial interaction between PS layerand PVA layer will be enhanced This technology is a feasiblemethod to avoid the exfoliation between PVA shell and PSsphere for the large hollow sphere

2 Experimental Section

21Materials Polystyrene (PS) and Polyvinyl Alcohol (PVA)are supplied by JampKChemical CompanyThenumber averagemolecular weight is 250 000 for PS and 124000-186000 forPVA respectively All other reagents and solvents were ana-lytical grade products and used without further purification

22The Surface Modification of PS Film and the Fabrication ofPS-PVABilayer Film Theprocedures of surfacemodificationfor PS filmwere conducted as follows PSwas first dissolved intoluene solvent with a proper concentration at 10 wt Thenthe PS solution was spin coated on a silicon substrate andthe toluene solvent was removedThe ozone treatment exper-iment was firstly conducted by dissolving ozone in waterat 25∘C The pH value was kept at 2 and the concentrationof ozone is 20wt The ozone was obtained by an ozonegenerator The PS film was immersed in water and its surfacewas ozonized in succession Different ozonization time on PSfilm was carried out

The PS-PVA bilayer film can be fabricated by spin coatingPVA solution on the PS film PVA was dissolved in waterand the weight concentration of PVA solution is 4wt Inaddition the thickness of PVA and PS layer is controlledwithin 15120583m The PS-PVA bilayer microsphere was fab-ricated by using microemulsification technology TypicallyPS solution was dripped into PVA solution together withrotational movement Finally PS-PVA bilayer microsphereswere obtained after the removal of solvents

23 Characterization Infrared spectra were measured byusing a Spectrum100 spectrometer (PerkinElmer Corpora-tion USA) with a transmission mode Ultraviolet-visible(UV-vis) absorption spectra were recorded on a Lambda900 (PerkinElmer Corporation USA) spectrometer Thegel permeation chromatography (GPC) measurement wasconducted in tetrahydrofuran solvent (WATERS1515 USA)Contact angle of PS films treated with ozone for differenttime was carried out by a JC2000X (China) machine inwater medium The interaction between PS and PVA wascharacterized by a Hysitron Triboindenter nano indenter(China)Themorphologies of sample were observed by usinga metalloscope optical microscopy (CANY C2003B China)The morphologies of film were sputter-coated with goldand observed by using a JSM-T300 (Japan) field emissionscanning electron microscopy with an accelerating voltage

4000 3500 3000 2500 2000 1500 1000 500

1720 cm-1

Wave number (cm )-1

(a) standard PS(b) ozonized PS (t=2h pH=2)

3447 cm-1

Figure 1 FTIR spectra of PS films (a) PS film ozonized at PH=2t=2h and (b) standard PS film

of 30 kV A Veeco WYKONT1100 (USA) white light interfer-ometer was used to obtain the surface shape of PS film withdifferent treatment

The adsorption of PVA onto PS film was calculated atroom temperature as follows First several standard PVAsolutions was prepared and the neat PS film and ozonizedPS films with different ozonization time were immersed inPVA solution The adsorption effect of PVA onto PS film canbe compared by using Ultraviolet-visible (UV-vis) absorptionspectra To quantify the effect of ozonization time on theadsorption of PVA onto PS film the adsorption ratio of PVAfor neat PS can be defined as 0 when the adsorption time is0min So the adsorption ratio of PVA for ozonized PS canbe calculated by comparing the absorption intensity of theneat PS and ozonized PS at different adsorbing time Theadsorption ratio (A) of PVA for ozonized PS with differentozonization time can be calculated by using

119860 = 119868119899 minus 119868119900119868119899 times 100 (2)

where 119868n is the absorption intensity of PVA for neat PSand 119868o is the absorption intensity of PVA for ozonized PSwithdifferent ozonization time

The morphology of PS-PVA bilayer microspheres wasobserved by using a microscopy (VHX-600E KEYENCEJapan) First the PS-PVA bilayer microspheres with largediameter (larger than 500120583m) were filtered by using a sieveThe diameter and the thickness of PS layer and PVA layerwere measured by an X-ray detector (TXF5011 USA)

3 Results and Discussion

31 IR Analysis The infrared spectra characterization of PSfilm before and after treated by ozone is shown in Figure 1Compared with the original PS film the surface modificationbrings about some different in its absorption peaks whenthe treated time is 2 h Two obvious absorption peaks at1720 cmminus1 and 3447 cmminus1 are observed clearly which should

Advances in Polymer Technology 3

2000 1900 1800 1700 160050

60

70

80

90

10min20min30min60min

120min180min420min

tran

smitt

ance

wavenumber (cm-1)

1710 cm-1

1746 cm-1

Figure 2 Change of absorption peak at 1720 cmminus1 with time on acertain condition (PH=2 T=323K)

be ascribed to the stretching vibration of carbonyl groupsand hydroxyl groups respectively By carefully analyzingthe changes of carbonyl groups the absorption intensityof carbonyl groups is enhanced with modification time inFigure 2 The absorption peak near 1720 cmminus1 is furtheranalyzed by double integration and nonlinear fitting and twonew weak absorption peaks (1710cmminus1 and 1746 cmminus1) can befound The possible reason is that the few ketone carbonylgroups exist on the modified PS surface while the carboxylgroups are still paly a dominated role This phenomenon iswell correlated with Liursquos report [24]Therefore the chemicalgroups on the ozonization modified PS surface are carboxylgroups and few ketone carbonyl groups

The amount of carbonyl and hydroxyl groups withozonization time on the PS film is measured by calculatingthe area of absorbing peaks The detailed date of these twofunctional groups at 323K is presented in Figure 3 It can beclearly seen that the amount of both carbonyl and hydroxylgroups are increased with ozonization time However theincrease tendency is different for the two groups Obviouslythe amount of the carbonyl groups is higher than that of thehydroxyl groupsThe possible reason for the increase of thesetwo groups with ozonization time is given as follows

The ozonization course [25 26] can be described as

O3 (S) 997888rarr O3 (T) 997888rarr O2 (1) +O (3P)997888rarr O2 +O (1D) (3)

The singlet ozone (O3(S)) is a stable substance while thetriplet ozone (O3(T)) is very unstable Therefore it is veryeasy for O3(T) to dissociate to the excited molecule oxy-gen gas (O2(1Δ))and the triplet-state oxygen atom (O(3P))respectively and the O(3P) will further transform to theexcited O(1D) The singlet state oxygen atom (1D) can

0 100 200 300 400 500

Abso

rban

ce

Ozonized time (min)carbonylhydroxyl

Figure 3 Increase of carbonyl content and hydroxyl content at thedifferent ozonized time

react with PS macromolecular chains through a concertedinsertion reaction into C-H and C-C bonds to form C-ORgroups while oxygen (3P) will react with molecular oxygenozone and other radicals through abstracting hydrogen fromthe polymer to leave a carbon radical leading to generatemore highly oxidized functionalities such as carbonyl andcarboxyl groups [27] By continue increasing the ozonizationtime the amount of carbonyl and hydroxyl groups willfurther increase Consequently the interaction between theozonized PS and the PVA will be enhanced because bothof them contain similar polar groups and this interactionwill be further enhanced by increasing the ozonization timeHowever excessive ozonization time will lead to severalundesirable outcomes One is the final physical properties ofozonized PS it will be impaired by introducing too muchcarbonyl and hydroxyl groups the other is containing toomuch carbonyl and hydroxyl groups and it will lead to theadhesion of PS microspheres by hydrogen bond interactionTherefore the proper ozonization time is 2 h by taking theamount of carbonyl and hydroxyl groups into consideration

32 GPCMeasurement To investigate the effect of surround-ing conditions on the ozonization PS series comparisonsare carried out by gel permeation chromatography in twodifferent pH values The two different pH values are 2 and 12As shown in Figure 4 the weight-average molecular weight(Mw) of PS in two different pH conditions is calculated Itcan be seen that the Mw of ozonized PS is different in theacidic and alkaline treating condition especially at higherozonization temperature Compared with the standard PSsample little difference is found for the Mw of ozonized PSin acidic surrounding (pHlt7) In contrast the degradationreaction will generate when the solution condition is alkalinein other words the alkaline treating condition will lead tothe degradation reaction The possible reason is that ozonemolecular can react with OH- in solution to produce OH2-


Table 1 Interaction force between PVA and PS

PS-PVA film Transverse crushing load Friction coefficient Axial load Indentation depthUntreated 1000 120583N 032 3000 120583N 890 nmOzonized 1400 120583N 038 3800 120583N 890 nm

283k 323k standard 283k 323k00

50x104

10x105

15x105

20x105

25x105pH=12

Mw

(gm

ol)

Samples

pH=2

Figure 4 The molecular weight value of the treated PS at thedifferent conditions

which can induce OH z radical The OH z radical has a highoxidation potential value of 280 eV This value is 35 higherthan that of ozone molecular so OH z radical can lead to thebroken of C-C for PS and further generatingwater and carbondioxide [24]Therefore the proper treating condition of PS isin acidic condition

33 Contact Angle and UV-vis Characterization The contactangle of a liquid on a solid surface depends on the physicaland chemical properties of the surface such as wettabilityhydrophilicity and roughness Thus measurement of thecontact angle on treated PS films gives information on thesurface propertiesThe contact angle for different ozonizationPS film to PVA is recorded to study the adsorption propertiesof PS to PVA results are presented in Figure 5(a) Figure 5(b)is the adsorption ratio of PS film to PVA for differentozonization time The ozonization modification technique ofPS film is at 323K and in acidic condition (pH=2) The PVAadsorption ratio of ozonized PS with different ozonizationtime is calculated by using equation (2) and the effect ofozonization time on the adsorption ratio of ozonized PSis shown in Figure 5(b) It can be clearly seen that theadsorption rate of neat PS film is 0 when the adsorbing timeis 0min and little difference is found by further increasing theadsorbing time However an obvious increase of adsorptionratio is found for the ozonized PS and this value will increasewith adsorbing time implying the enhancement of interfacialinteraction between PS and PVA by ozone treatment

Before ozonization modification the contact angle of PSto PVA is 985∘ After ozonization for 1 h this contact angledecreases to 82∘ while the adsorption rate of PS to PVAis enhanced Those phenomena revealed that the surfaceof PS film has turned from hydrophobic to hydrophilic

which is in agreement with Dengteng Ge [28] The reasonis that the surfaces of ozonization PS film generate carbonyland hydroxyl groups which will have strong effect withthe hydroxyl groups of PVA by hydrogen bonding [7]Consequently the adsorption rate will be enhanced

Obviously the contact angle of PS to PVA decreasedwith the ozonization time and the adsorption rate of PVAgradually increased This phenomenon is well correlatedwith the IR results which demonstrated that the amountof carbonyl and hydroxyl groups is increasing with theozonization time The generation of these functional groupscan enhance the interfacial interaction between PS and PVA

34 The Toughening Effect of Ozonization PS and the Interfa-cial Interaction between PS and PVA The polarizing opticalmicroscopy observation of surface morphologies for PS filmbefore and after ozonization is shown in Figure 6 Halfside of the PS film was protected to avoid the ozonizationwhile the other half side was treated by ozone then the filmwas immersed into water at 10∘C to compare their differentstress cracking behaviors After few hours the half side ofthe film without ozonization modification began to exhibitcracks While the other half side of the film began to exhibitcracks after 3 days There is an obvious difference for thecracks morphologies among the two sides The shape of thecracks is dendritic and spherical in the left and right siderespectively These two different cracks are correspondedto brittle and ductile fracture Therefore the ozonizationmodification can result in the toughness of PS film also canstop the development of cracks

A nano indenter experiment [29] was conducted to char-acterize the interfacial strength between PS and PVA layerseach layer is 800 nm The effect of ozonization modificationof PS on the interfacial between PS and PVA was analyzedWhen a critical loading is carried a sudden change offriction coefficient will appear Therefore the sudden changeof friction coefficient can be used to judge the interfacialdebonding of PS and PVA The calculated data of twodifferent systems was listed in Table 1 one is for the untreatedPS coated PVA and the other is for the ozonization PS andPVA (the ozonization condition is at room temperature for2 h in acidic condition pH=2) Obviously the critical loadingof layers between ozonized PS and PVA is increased by 40compared with that of untreated PS and PVA which indicatesthat the interfacial interaction between ozonized PS and PVAis enhanced This result is well complied with the increaseadsorption between PS and PVA in Figure 5(b)

35 The Effect of Ozonization on the Surface Morphologiesof PS Film The effect of ozonization time on the surfacemorphologies of PS film is shown in Figure 7 Compared withthe smooth surface of the untreated PS some concaves were


0 1 2 3 4

70

75

80

85

90

95

100C

onta

ct A

ngle

ozonized time (h)

(a) Contact angle of surfactant functionalized PS films with differentozonized time

0 20 40 60 80 100 120 140 160 180 20000

05

10

15

20

25

30

35

40

Standard PSOzonized 05 hOzonized 1 hOzonized 2 h

Ozonized 3 hOzonized 4 hOzonized 5 h

Adso

rptio

n ra

tio (

)

Time (min)

(b) PVA adsorption for ozonated PS films with different ozonized time

Figure 5 Contact angle and PVA adsorption of ozonated PS films with different ozonized time

Figure 6 Pictures of the surface of PS film before and after ozonization

found on the surface of PS film after ozonization at 323KThese concaves resulted from the chemical reaction betweenPS chains and ozone [30ndash33] The average diameter ofconcaves is about 3120583m and the amount of concaves increaseswith the ozonization time The existence of these concavescan benefit the enhancement of the interfacial interactionbetween PS and PVA by providing large anchoring spotsFigure 8 is the thickness map collected from the white lightinterferometer for the ozonized PS filmThe ozonization timeis 2 h and the pH value is 2 It can be clearly seen that thesurface of ozonized PSfilm is not very coarse and a fewdefectsare found on this surface However serious problem will bebrought about when the ozonization time is as long as 8 hbecause too many concaves will deteriorate the mechanicalproperties of PS film

It is known that the survival rate of PS-PVA hollowmicrosphere with large diameter will be restrained dueto the large deformation of each layer on the basis ofCox equation Therefore the interaction between PS andPVA layer should be enhanced to fabricate large hollowmicrosphere with excellent stability The enhancement of theinteraction between PS and PVA through ozone treatment

will lead to the increasing of stability for PS-PVA bilayermicrospheres with large dimension (the diameter is largerthan 500120583m) Figure 9 is the pictures of the bilayer PS-PVAmicrospheres treated by ozone The thickness of each layerand the survival rate of PS-PVA hollow microsphere withlarge diameter are listed in Tables 2 and 3 respectively Theaverage diameter of PS-PVA bilayer microspheres can reachto 778120583mAfter ozone treatment the survival rate of PS-PVAhollow microsphere with large diameter is increased to 50a remarkable enhancement compared with the untreated PS-PVA one

4 Conclusion

The ozonization modification method was conducted to thePS film to enhance the interfacial interaction between PS andPVA in this paper The experimental results revealed thatthe carbonyl and hydroxyl groups were introduced to thesurface of PS and the amount of functional groups increasedwith the ozonization timeThepropermodification conditionis in acidic condition After ozonization modification thehydrophilic PS was improved and the adsorption of PS to


Table 2 Parameters of the PS-PVA bilayer hollow microspheres

Diameter of PS-PVA(120583m)

Thickness of PS-PVAbilayer (120583m)

Thickness of PVA(120583m) Thickness of PS (120583m)

77835 1364 326 1038

Table 3 Survival rate of PS-PVA hollow microspheres of large diameter (larger than 500120583m)

Active agent Neat PS Ozonized PSSurvival rate of PS-PVA hollow microsphere () lt1 sim50

(a) Standard PS film (b) pH=2 T=323K 1h

(c) pH=2 T=323K 2h (d) pH=2 T=323K 8h

Figure 7The SEM pictures of the surface of PS film at the different condition

nm121

100

50

0

minus50

minus100

minus140

Surface Stats

Ra 285nm

Rq 448nm

Rt 26103nm

Measurement Info

Magnification 509

Measurement Mode PSI

Sampling 165um

Array Size 736X480

Figure 8 The pictures of the surface of PS film after ozonization at pH=2 T=323K and t=2h


(a) (b) (c)

Figure 9The microscope and X-ray pictures of PS-PVA bilayer hollow microspheres (a) ((b) is the picture with magnification of 200 for (a)and (c) is the X-ray picture of (a))

PVA was also enhanced The introduction of the hydrophilicgroups could lead to the enhancement interfacial interactionbetween PS and PVA film Therefore the interfacial debond-ing of the PS-PVA bilayer hollow microspheres could beavoided by this ozonization technique

Data Availability

The data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors are grateful to the China Academy of Engineer-ing Physics for financial support (2014B0302052)

References

[1] M F Liu S F Chen X B Qi et al ldquoImprovement ofwall thickness uniformity of thick-walled polystyrene shells bydensity matchingrdquo Chemical Engineering Journal vol 241 pp466ndash476 2014

[2] J Li L Su M F Liu et al ldquoInfluence of sucrose on the stabilityof W1OW2 double emulsion dropletsrdquo RSC Advances vol 5p 83089 2015

[3] X J Zhang J Li K Cao Y Yi J X Yang and B Li ldquoSynthesisand characterization ofBndashCpolymer hollowmicrospheres froma new organodecaborane preceramic polymerrdquo RSC Advancesvol 5 p 86214 2015

[4] R R Paguio C A Frederick J F Hund et al ldquoFabricationcapabilities for spherical foam targets used in ICF experimentsrdquoin Proceedings of the 17th Target Fabrication Specialist MeetingSan Diego CA USA 2006

[5] L Su J Li J Li et al ldquoInfluence of ionic surface active agenton distribution properties of PS-PVA double emulsionrdquo HighPower Laser and Particle Beams vol 26 no 2 Article ID022012(5) 2014

[6] Y Honarpazhouh F R Astaraei H R Naderi and O TavakolildquoElectrochemical hydrogen storage in Pd-coated porous sili-congraphene oxiderdquo International Journal of Hydrogen Energyvol 41 no 28 pp 12175ndash12182 2016

[7] L Su J Li Q M Chu et al ldquoEffect of Tween 20 nonionicsurfactant on preparation of large size double-layer hollowmicrospheresrdquoHigh Power Laser and Particle Beams vol 27 no12 Article ID 27122007 2015

[8] Q Chen S F ChenM F Liu et al ldquoInfluence of fluorobenzenemass transfer on the qualities of poly-120572-methylstyrene shellsrdquoRSC Advances vol 8 pp 3687ndash3693 2018

[9] M F Liu Y Q Zheng J Li et al ldquoEffects of molecular weightof PVA on formation stability and deformation of compounddroplets for ICF polymer shellsrdquo Nuclear Fusion vol 57 no 1Article ID 016018 2017

[10] S Tasoglu G Kaynak A J Szeri U Demirci and MMuradoglu ldquoImpact of a compound droplet on a flat surfacea model for single cell epitaxyrdquo Physics of Fluids vol 22 no 8Article ID 082103 2010

[11] P Gao and J J Feng ldquoSpreading and breakup of a compounddrop on a partially wetting substraterdquo Journal of Fluid Mechan-ics vol 682 pp 415ndash433 2011

[12] L Su S F Chen M F Liu et al ldquoResearch progress offabricating polyvinyl alcohol coating on plastic microsphererdquoHigh Power Laser and Particle Beams vol 24 no 7 pp 1517ndash1522 2012

[13] R G Cox ldquoThe deformation of a drop in a general time-dependent fluid flowrdquo Journal of Fluid Mechanics vol 37 no 3pp 601ndash623 1969

[14] T N Murakami Y Fukushima Y Hirano Y Tokuoka MTakahashi and N Kawashima ldquoModification of PS films bycombined treatment of ozone aeration and UV irradiation inaqueous ammonia solution for the introduction of amine andamide groups on their surfacerdquoApplied Surface Science vol 249p 425 2005

[15] L F Macmanus M J Walzak and N S Mcintyre ldquoStudy ofultraviolet light and ozone surface modification of polypropy-lenerdquo Journal of Polymer Science Part A Polymer Chemistry vol37 no 14 p 2489 1999

[16] E Harel S E Meltzer A A G Requicha M EThompson andB E Koel ldquoFabrication of polystyrene latex nanostructures bynanomanipulation and thermal processingrdquo Nano Letters vol5 no 12 p 2624 2005

[17] L Wang S B Gao J J Wang W C Wang L Q Zhang andM Tian ldquoSurface modification of UHMWPE fibers by ozonetreatment and UV grafting for adhesion improvementrdquo TheJournal of Adhesion vol 94 no 1 pp 30ndash45 2018

[18] T Clark Jr J D Ruiz H Fan C J Brinker B I Swanson andA N Parikh ldquoA new application of UVminusozone treatment in


the preparation of substrate-supportedmesoporous thin filmsrdquoChemistry of Materials vol 12 p 3879 2000

[19] M R Davidson S A Mitchell and R H Bradley ldquoUV-ozone modification of plasma-polymerised acetonitrile filmsfor enhanced cell attachmentrdquo Colloids and Surfaces B Bioin-terfaces vol 34 no 4 pp 213ndash219 2004

[20] X Yu A Beharaj M W Grinstaff and O K C Tsui ldquoModu-lation of the effective viscosity of polymer films by ultravioletozone treatmentrdquo Polymer Journal vol 116 pp 498ndash505 2017

[21] P L Yue ldquoModelling of kinetics and reactor for water purifica-tion by photo-oxidationrdquo Chemical Engineering Science vol 48no 1 pp 1ndash11 1993

[22] T NMurakami Y FukushimaY Hirano Y Tokuoka M Taka-hashi and N Kawashima ldquoSurface modification of polystyreneand poly(methyl methacrylate) by active oxygen treatmentrdquoColloids and Surfaces B Biointerfaces vol 29 no 2-3 pp 171ndash179 2003

[23] T N Murakami M Takahashi and N Kawashima ldquoDecom-position of aromatic compounds by active oxygen generatorrdquoChemistry Letters vol 29 no 11 pp 1312-1313 2000

[24] Y Y Liu Q B Kan S Wei Z W Zhang and S F ChenldquoSurface modification of PS films by ozonerdquo High Power Laserand Particle Beams vol 23 no 1 p 111 2011

[25] P Somathilake J A Dominic G Achari C H Langford andJ-H Tay ldquoDegradation of carbamazepine by photo-assistedozonation influence of wavelength and intensity of radiationrdquoOzone Science amp Engineering vol 40 no 2 pp 113ndash121 2018

[26] C Ding D K Yuan Z H Wang et al ldquoOzone productioninfluenced by increasing gas pressure inmultichannel dielectricbarrier discharge for positive and negative pulsemodesrdquoOzoneScience amp Engineering vol 40 no 3 p 228 2018

[27] D O H Teare C Ton-That and R H Bradley ldquoSurfacecharacterization and ageing of ultravioletndashozone-treated poly-mers using atomic force microscopy and x-ray photoelectronspectroscopyrdquo Surface and Interface Analysis vol 29 no 4 p276 2000

[28] D T Ge Y Li L L Yang Z Fan C Liu and XZhang ldquoImproved self-assembly through UVozone surface-modification of colloidal spheresrdquoThin Solid Films vol 519 pp5203ndash5207 2011

[29] Z H Hodzic J Stachurski and K Kim ldquoNano-indentation ofpolymerndashglass interfaces part I Experimental and mechanicalanalysisrdquo Polymer vol 41 no 18 pp 6895ndash6905 2000

[30] R Yang Q H He C H Wang and S Q Sun ldquoSurface mod-ification of polystyrene microsphere using ozone treatmentrdquoFerroelectrics vol 530 no 1 pp 130ndash135 2018

[31] Z Yoshimitsu A Nakajima T Watanabe and K HashimotoldquoEffects of surface structure on the hydrophobicity and slidingbehavior of water dropletsrdquo Langmuir vol 18 no 15 pp 5818ndash5822 2002

[32] S AMitchell A H C PoulssonM R Davidson N EmmisonA G Shard and R H Bradley ldquoCellular attachment and spatialcontrol of cells using micro-patterned ultra-violetOzone treat-ment in serumenrichedmediardquo Biomaterials vol 25 no 18 pp4079ndash4086 2004

[33] D O H Teare C Ton-That and R H Bradley ldquoSurfacecharacterization and ageing of ultravioletndashozone-treated poly-mers using atomic force microscopy and x-ray photoelectronspectroscopyrdquo Surface and Interface Analysis vol 29 pp 276ndash283 2000

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surface modification for its easy procedure and low cost [14ndash20] Once polymer is exposed in ozone atmosphere somecarbonyl groups and carboxyl groups will appear on thepolymer chains In addition some peroxide groups will alsogenerate The peroxide group will change to hydroxyl groupafter ultraviolet illumination or heated Consequently thesurface of polymer will become hydrophilic to some extent[19 21ndash23] Then the interfacial interaction between PS layerand PVA layer will be enhanced This technology is a feasiblemethod to avoid the exfoliation between PVA shell and PSsphere for the large hollow sphere

2 Experimental Section

21Materials Polystyrene (PS) and Polyvinyl Alcohol (PVA)are supplied by JampKChemical CompanyThenumber averagemolecular weight is 250 000 for PS and 124000-186000 forPVA respectively All other reagents and solvents were ana-lytical grade products and used without further purification

22The Surface Modification of PS Film and the Fabrication ofPS-PVABilayer Film Theprocedures of surfacemodificationfor PS filmwere conducted as follows PSwas first dissolved intoluene solvent with a proper concentration at 10 wt Thenthe PS solution was spin coated on a silicon substrate andthe toluene solvent was removedThe ozone treatment exper-iment was firstly conducted by dissolving ozone in waterat 25∘C The pH value was kept at 2 and the concentrationof ozone is 20wt The ozone was obtained by an ozonegenerator The PS film was immersed in water and its surfacewas ozonized in succession Different ozonization time on PSfilm was carried out

The PS-PVA bilayer film can be fabricated by spin coatingPVA solution on the PS film PVA was dissolved in waterand the weight concentration of PVA solution is 4wt Inaddition the thickness of PVA and PS layer is controlledwithin 15120583m The PS-PVA bilayer microsphere was fab-ricated by using microemulsification technology TypicallyPS solution was dripped into PVA solution together withrotational movement Finally PS-PVA bilayer microsphereswere obtained after the removal of solvents

23 Characterization Infrared spectra were measured byusing a Spectrum100 spectrometer (PerkinElmer Corpora-tion USA) with a transmission mode Ultraviolet-visible(UV-vis) absorption spectra were recorded on a Lambda900 (PerkinElmer Corporation USA) spectrometer Thegel permeation chromatography (GPC) measurement wasconducted in tetrahydrofuran solvent (WATERS1515 USA)Contact angle of PS films treated with ozone for differenttime was carried out by a JC2000X (China) machine inwater medium The interaction between PS and PVA wascharacterized by a Hysitron Triboindenter nano indenter(China)Themorphologies of sample were observed by usinga metalloscope optical microscopy (CANY C2003B China)The morphologies of film were sputter-coated with goldand observed by using a JSM-T300 (Japan) field emissionscanning electron microscopy with an accelerating voltage

4000 3500 3000 2500 2000 1500 1000 500

1720 cm-1

Wave number (cm )-1

(a) standard PS(b) ozonized PS (t=2h pH=2)

3447 cm-1

Figure 1 FTIR spectra of PS films (a) PS film ozonized at PH=2t=2h and (b) standard PS film

of 30 kV A Veeco WYKONT1100 (USA) white light interfer-ometer was used to obtain the surface shape of PS film withdifferent treatment

The adsorption of PVA onto PS film was calculated atroom temperature as follows First several standard PVAsolutions was prepared and the neat PS film and ozonizedPS films with different ozonization time were immersed inPVA solution The adsorption effect of PVA onto PS film canbe compared by using Ultraviolet-visible (UV-vis) absorptionspectra To quantify the effect of ozonization time on theadsorption of PVA onto PS film the adsorption ratio of PVAfor neat PS can be defined as 0 when the adsorption time is0min So the adsorption ratio of PVA for ozonized PS canbe calculated by comparing the absorption intensity of theneat PS and ozonized PS at different adsorbing time Theadsorption ratio (A) of PVA for ozonized PS with differentozonization time can be calculated by using

119860 = 119868119899 minus 119868119900119868119899 times 100 (2)

where 119868n is the absorption intensity of PVA for neat PSand 119868o is the absorption intensity of PVA for ozonized PSwithdifferent ozonization time

The morphology of PS-PVA bilayer microspheres wasobserved by using a microscopy (VHX-600E KEYENCEJapan) First the PS-PVA bilayer microspheres with largediameter (larger than 500120583m) were filtered by using a sieveThe diameter and the thickness of PS layer and PVA layerwere measured by an X-ray detector (TXF5011 USA)

3 Results and Discussion

31 IR Analysis The infrared spectra characterization of PSfilm before and after treated by ozone is shown in Figure 1Compared with the original PS film the surface modificationbrings about some different in its absorption peaks whenthe treated time is 2 h Two obvious absorption peaks at1720 cmminus1 and 3447 cmminus1 are observed clearly which should


2000 1900 1800 1700 160050

60

70

80

90


120min180min420min

tran

smitt

ance

wavenumber (cm-1)

1710 cm-1

1746 cm-1







0 100 200 300 400 500

Abso

rban

ce









50x104

10x105

15x105

20x105

25x105pH=12

Mw

(gm

ol)

Samples

pH=2











0 1 2 3 4

70

75

80

85

90

95

100C

onta

ct A

ngle

ozonized time (h)


0 20 40 60 80 100 120 140 160 180 20000

05

10

15

20

25

30

35

40



Adso

rptio

n ra

tio (

)

Time (min)







4 Conclusion







77835 1364 326 1038




(c) pH=2 T=323K 2h (d) pH=2 T=323K 8h


nm121

100

50

0

minus50

minus100

minus140

Surface Stats

Ra 285nm

Rq 448nm

Rt 26103nm

Measurement Info

Magnification 509


Sampling 165um

Array Size 736X480



(a) (b) (c)



Data Availability




Acknowledgments


References






































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


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2000 1900 1800 1700 160050

60

70

80

90


120min180min420min

tran

smitt

ance

wavenumber (cm-1)

1710 cm-1

1746 cm-1







0 100 200 300 400 500

Abso

rban

ce









50x104

10x105

15x105

20x105

25x105pH=12

Mw

(gm

ol)

Samples

pH=2











0 1 2 3 4

70

75

80

85

90

95

100C

onta

ct A

ngle

ozonized time (h)


0 20 40 60 80 100 120 140 160 180 20000

05

10

15

20

25

30

35

40



Adso

rptio

n ra

tio (

)

Time (min)







4 Conclusion







77835 1364 326 1038




(c) pH=2 T=323K 2h (d) pH=2 T=323K 8h


nm121

100

50

0

minus50

minus100

minus140

Surface Stats

Ra 285nm

Rq 448nm

Rt 26103nm

Measurement Info

Magnification 509


Sampling 165um

Array Size 736X480



(a) (b) (c)



Data Availability




Acknowledgments


References






































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls








50x104

10x105

15x105

20x105

25x105pH=12

Mw

(gm

ol)

Samples

pH=2











0 1 2 3 4

70

75

80

85

90

95

100C

onta

ct A

ngle

ozonized time (h)


0 20 40 60 80 100 120 140 160 180 20000

05

10

15

20

25

30

35

40



Adso

rptio

n ra

tio (

)

Time (min)







4 Conclusion







77835 1364 326 1038




(c) pH=2 T=323K 2h (d) pH=2 T=323K 8h


nm121

100

50

0

minus50

minus100

minus140

Surface Stats

Ra 285nm

Rq 448nm

Rt 26103nm

Measurement Info

Magnification 509


Sampling 165um

Array Size 736X480



(a) (b) (c)



Data Availability




Acknowledgments


References






































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





0 1 2 3 4

70

75

80

85

90

95

100C

onta

ct A

ngle

ozonized time (h)


0 20 40 60 80 100 120 140 160 180 20000

05

10

15

20

25

30

35

40



Adso

rptio

n ra

tio (

)

Time (min)







4 Conclusion







77835 1364 326 1038




(c) pH=2 T=323K 2h (d) pH=2 T=323K 8h


nm121

100

50

0

minus50

minus100

minus140

Surface Stats

Ra 285nm

Rq 448nm

Rt 26103nm

Measurement Info

Magnification 509


Sampling 165um

Array Size 736X480



(a) (b) (c)



Data Availability




Acknowledgments


References






































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls









77835 1364 326 1038




(c) pH=2 T=323K 2h (d) pH=2 T=323K 8h


nm121

100

50

0

minus50

minus100

minus140

Surface Stats

Ra 285nm

Rq 448nm

Rt 26103nm

Measurement Info

Magnification 509


Sampling 165um

Array Size 736X480



(a) (b) (c)



Data Availability




Acknowledgments


References






































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





(a) (b) (c)



Data Availability




Acknowledgments


References






































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls























Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




enhancement of the interlayer interaction between...

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