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  • ORIGINAL PAPER

    A water-soluble organic-inorganic hybrid material basedon polyhedral oligomeric silsesquioxane and polyvinyl alcohol

    Xiaojing Zhang & Chunmian Yan & Shaoming Fang &Chenggui Zhang & Tiangang Jia & Yi Zhang

    Received: 22 June 2009 /Accepted: 22 September 2009 /Published online: 3 October 2009# Springer Science + Business Media B.V. 2009

    Abstract A novel series of organic-inorganic hybridmaterials involving cage-like octa(3-chloroammonium-propyl)silsesquioxane and Polyvinyl alcohol (OCAPS/PVA) were prepared via solution blending method. Theobtained hybrid films were optically transparent and solublein water. OCAPS/PVA hybrids were characterized by FT-IR,wide-angle X-ray diffraction (WAXD) scanning electronicmicroscopy (SEM), energy dispersive X-ray spectroscopy(EDS), differential scanning calorimetry (DSC), thermog-ravimetry analysis (TGA) and tensile test. The resultsshowed that the hydrogen bond interactions were formedbetween OCAPS and PVA. OCAPS could be dispersed wellin PVA matrix till its content was 10 wt%, while theaggregation and crystallization of OCAPS were observedwhen the content was up to 15 wt%. The glass transitiontemperature (Tg) of OCAPS/PVAwas found to increase from53 C to 60 C, and the melting temperature (Tm) decreasedfrom 180 C to 171 C with increasing OCAPS content from0 wt% to 15 wt%. The thermal stability of PVA main chainwas improved by the addition of OCAPS and the thermalresidue ratio also increased. The tensile strength of OCAPS/PVA decreased from 28 MPa to 19 MPa, while theelongation at break of hybrid films increased from 121% to175%.

    Keywords Polyhedral oligomeric silsesquioxane .

    Polyvinyl alcohol . Hybrid materials . Thermal properties .

    Mechanical properties

    Introduction

    Organic-inorganic hybrid materials have been paid on muchattention in the last decades due to the synergetic effect oforganic and inorganic components in nanoscales. Thecombination of organic and inorganic components isexpected to provide remarkable and complementary prop-erties, which cannot be obtained with a single material. Themost widely used synthetic approach is via the sol-geltechnique for preparing inorganic oxides at ambienttemperature by hydrolysis and condensation of alkoxysi-lanes and other metal alkoxides [1, 2]. Organic phases (suchas polymers) could be incorporated without any separationinto the silica matrix by using covalent bond or physicalinteractions between two phases or by controlling gelationof polymers and formation of silica gel through variousmolecular designs [3, 4]. Although the organic-inorganicpolymer hybrids prepared by the sol-gel reaction ofalkoxysilanes are known to have good properties such ashigh thermal stability and high strength, the obtained hybridmaterials could not be soluble again in any organic solventsbecause of the covalently crosslinking structure in thesilica-polymer matrix. The insolubility has limited thewidely use of organic-inorganic hybrid materials preparedby sol-gel method [5, 6].

    Apparently, water-soluble hybrid materials will breakthis limitation and start a new future, but research in thisfield has still been limited up to now. Wunder et al.synthesized an oligo(ethyleneoxide)-functionalized silses-quioxane, in which the hydrophilic oligo(ethyleneoxide)was linked to a cubic silsesquioxane core via hydro-silylation reaction [7]. Frey et al. and He et al. preparedmonosubstituted and multiarm poly(ethylene oxide)-cubicsilsesquioxane that were also water-soluble, whose solutionproperties and aggregation behavior were investigated

    X. Zhang (*) : C. Yan : S. Fang :C. Zhang : T. Jia :Y. ZhangCollege of Materials and Chemical Engineering,Henan Provincial Key Laboratory of Surface and InterfaceScience, Zhengzhou University of Light Industry,Zhengzhou 450002, Peoples Republic of Chinae-mail: zhangxj@iccas.ac.cn

    J Polym Res (2010) 17:631638DOI 10.1007/s10965-009-9351-2

  • [8, 9]. Recently, Mori et al. reported the synthesis andcharacterization of water-soluble silsesquioxane-based nano-particles that were prepared by hydrolytic condensation ofdifferent triethoxysilane precursors [10, 11].

    Silsesquioxanes is a special kind of siloxane compoundwith the emperical formula (RSiO1.5)n where R ishydrogen, or any alkyl, alkylene, aryl, arylene, ororgano-functional derivatives of the above groups. Thestructures of silsesquioxanes have been reported asrandom structure, ladder structure, cage structures, andpartial cage structure. Among them, polyhedral oligomericsilsesquioxane(POSS) has been paid on more attentionsrecently as a new class of nanofillers for preparation oforganic-inorganic hybrid materials. It generally consists ofthree-dimensional, rigid inorganic cores (Si-O cages) andflexible organic coronae, and can be considered to be thesmallest silica particles (13 nm) [1214]. POSS may beincorporated into a polymer matrix in two primary ways:chemically tethered to the polymer backbone or physicallyblended with the polymer matrix as untethered fillerparticles. The properties of hybrid polymers such asthermal stability usually have been enhanced when POSSwas covalently tethered to a polymer backbone [1518].Compared to the extensive reports about covalently POSS-polymer hybrid system, research about POSS/polymerhybrid materials prepared by physical blending has beenlimited [1921]. The physical blending method is simpleto use and fit to prepare materials on the large scale, whilewith the shortcoming of poor miscibility between POSS andpolymer matrix if no special interface interactions areinvolved in the blended materials. An enhanced compatibilityis expected when the substitute groups of POSS are similar orhave relative strong interactions with the polymer.

    Cage-like octa(3-chloroammoniumpropyl)silsesquioxane(OCAPS) with functional amino groups has good solubilityin water (Fig. 1), which is usually utilized as the buildingblocks of molecular assembly, drug control released

    materials, DNA delivery and so on [2225]. Till now, thereare a few reports about Polyvinyl alcohol (PVA)/silicahybrid materials by sol-gel methods [26, 27], yet water-soluble hybrid materials based on OCAPS and PVA as wellas their properties are seldom reported. In this report, aseries of hybrid materials involving OCAPS and PVA wereprepared via solution blending method, in which thehydrogen bonds were formed between amino group ofOCAPS and hydroxyl or carbonyl group of PVA. Thecompatibility and interactions between OCAPS and PVA aswell as the effects of OCAPS on the thermal andmechanical properties of PVA were investigated by FT-IR,wide-angle X-ray diffraction (WAXD), scanning electronicmicroscopy (SEM), energy dispersive X-ray spectroscopy(EDS), differential scanning calorimetry (DSC), thermog-ravimetry analysis (TGA) and tensile test.

    Experimental

    Materials

    3-Aminopropyltriethoxysilane was analytical pure gradeand purchased from Nanjing Shuguang Chemical Co. Ltd;PVA was purchased from KuRaRay Co. Ltd. (DP=1,700,degree of hydrolysis = 88%); All the other reagents wereanalytical pure grade and used as received. The synthesis ofOCAPS was according to literature 22 and 28. Thecharacterization data are as follows: FT-IR (KBr, cm1):3,224, 3,025, 1,604, 1,494, 1,122, 935 cm1; 1H-NMR(400 MHz, D2O): 4.68 (s, NH3, 24 H), 2.94(t, CH2NH3,16 H), 1.70 (m, SiCH2CH2, 16 H), 0.71 (t, SiCH2, 16 H);29Si-NMR (71.5 MHz, D2O): 66.4 (s).

    Preparation of OCAPS/PVA hybrid films

    The OCAPS solution was added quickly into 15 wt% (inmass, the same below) water solution of PVA afterultrasonic oscillation for 20 min. Then the mixed solutionwas stirred for 1 hr and treated by ultrasonic oscillation for30 min to make OCAPS disperse well in PVA matrix.Finally, OCAPS/PVA hybrid films were prepared insolution casting method and the contents of OCAPS were3 wt%, 5 wt%, 10 wt% and 15 wt% respectively.

    Characterization

    The FT-IR spectra of the neat polymer and the hybrid filmswere recorded in the range 4,000600 cm1 at a resolutionof 4.0 cm1 with a Bruker Tensor 27 FT-IR spectrometer(Germany); Dispersion of OCAPS in the polymer matrixwas observed through microscopic investigations using aJEOL JSM 6490LV SEM with an acceleration voltage of

    SiO Si

    O

    O

    O

    O

    Si SiOO

    O

    Si SiO

    Si SiO

    O

    O

    NH3+Cl-

    NH3+Cl-

    NH3+Cl-

    NH3+Cl--Cl+H3N

    -Cl+H3N

    -Cl+H3N

    -Cl+H3N

    Fig. 1 Scheme of the structure of OCAPS

    632 X. Zhang et al.

  • 10 kV. The samples were sputter coated with gold in orderto avoid the artifacts associated with sample charging. TheX-ray silicon mapping of the hybrid films was recorded inan Oxford EDS system, attached to the microscope. WAXDspectra were recorded on a Bruker D8 ADVANCEapparatus with a Ni-filtered Cu-K radiation, 40 kV,100 mA electric current, and a scanning rate of 2/min.The scanning range of 2 was from 360. Calorimetricmeasurements were performed on a Bruker Q100 DSC innitrogen atmosphere at a heating rate of 10 C/min. Allsamples (about 5 mg in weight) were heated from 30 C to210 C. Themogravimetric analysis of the hybrid materialswas performed by using a NETZSCH-499C TGA instru-ment from ambient temperature to 700 C with a heatingrate of 10 C/min in nitrogen atmosphere. A sampleweight of 10 mg was taken for all the measurements. Theweight loss against temperature was recorded. Tensilemechanical tests were carried out using a CMT-6104

    Electronic Universal Testing Machine (MTI Systems Co.Ltd., Shenzhen, China) according to GB/T1040-92 stan-dard. The samples are double-bell and measured at a strainrate of 30 mm/min. All the reported results are an averageof at least six successful measurements for the tensiledeterminations.

    Results and discussion

    Preparation of OCAPS/PVA hybrid films

    OCAPS was prepare

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