synthesis and characterization of poly(trimethylene terephthalate)/polyhedral oligomeric...

Synthesis and Characterization ofPoly(trimethylene terephthalate)/PolyhedralOligomeric Silsesquixanes Nanocomposites

Kap Jin Kim, Subramaniyan Ramasundaram, Jong Soon LeeDepartment of Advanced Polymer and Fiber Materials, College of Environment and Applied Chemistry,Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, South Korea

This article reports the preparation of poly(trimethyleneterephthalate) (PTT)– polyhedral oligomeric silsesquiox-anes (POSS) nanocomposites through in situ polymer-ization. The chemical structure of the PTT–POSS nano-composites was characterized with Fourier-transforminfrared and nuclear magnetic resonance spectroscop-ies and the presence of POSS was further confirmedby the elemental analysis. The crystal structures aswell as the position of POSS in the nanocompositeswere ascertained by the X-ray diffraction (XRD) studies.Thermal characterization studies showed the gradualdecrease in the glass transition and melt crystallizationtemperatures. Though the thermal stability of the PTTwas not affected by the incorporation of POSS, theamount of residues obtained from thermal degradationprocess was increased with an increase in the contentof POSS. The tensile studies showed that the values ofinitial modulus and breaking strength were dramaticallydecreased with an increase in the content of POSS.POLYM. COMPOS., 29:894–901, 2008. ª 2008 Society of Plas-tics Engineers

INTRODUCTION

Polyhedral oligomeric silsesquioxanes (POSS) are the

smallest particles of the organosilica that contains a nano-

structured polyhedral silicone–oxygen (2:3) skeleton or

cage, with a precisely defined Si��Si diameter of 0.53

nm. There are 8–12 silicon atoms in a cage with the same

number of organic functional groups in its surroundings

and the total structure of the POSS is often denoted using

the empirical, Rn(SiO1.5)n. It is possible to attach different

kinds of functional or nonfunctional (R) groups to the

corner Si molecules to suit the requirements precisely [1, 2].

Because of this versatility of POSS chemistry, it finds a

variety of applications from low dielectric constant mate-

rials to new electron beam lithography. Among the vari-

ous applications of POSS, the most important field is the

preparation of polymer nanocomposites and hybrids, with

the aim to obtain multifunctional materials having the

intermediate properties between organic polymers and

ceramics [3]. In the polymer-POSS nanocomposites, the

POSS acts as a nanoscaled building block and its molecu-

lar level interaction with the polymers is believed to be

helpful for the efficient reinforcement. Generally, the

POSS molecules are incorporated into the polymer matrix

by copolymerization, grafting, or even blending using the

traditional processing methods. In recent years, the POSS

molecules have been successfully dispersed or incorpo-

rated into the various commercial polymers such as poly-

methacrylates [4], polystyrenes [5], polyethylene [6],

polynorboranes [7], polyurethanes [8], polyamides [9–11],

polyimides [12], polyepoxides [13], etc.

However, there have been only a few articles concern-

ing polyester-POSS nanocomposites. While Zeng et al.

prepared the poly(ethylene terephthalate)-POSS (PET–

POSS) nanocomposites using both reactive and nonreac-

tive POSS molecules [14] and Yoon et al. reported the

properties of PET containing epoxy-functionalized POSS

[15], no attention has been paid to the preparation of poly

(trimethylene terephtahlate)- POSS (PTT–POSS) nano-

composites. It is well known that PTT, below or near its

Tg, undergoes a phenomenon of physical aging, involving

changes in its polymer properties, that influences its per-

formance and lifetime for fiber and engineering thermo-

plastic applications [16]. In this study, an attempt has

been made to prepare the PTT–POSS nanocomposites

with the aim to overcome this disadvantage by the addi-

tion of copolymerizable 1,2-propanediolisobutyl-POSS

(PDIB–POSS) in the course of PTT polymerization.

In addition to the intrinsic merits of PTT such as high

elastic recovery, low fiber modulus, and resilience attrib-

uted to the highly contracted and coiled gauche–gauche

Author Jong Soon Lee is currently at Material Analysis Team, Central

Research Institute, Hyosung Corporation, Anyang-si, Gyeonggi-do 431-

080, South Korea.

Contract grant sponsor: Kyung Hee University; contract grant number:

KHU-20040224.

Correspondence to: Kap Jin Kim; e-mail: [email protected]

DOI 10.1002/pc.20471

Published online in Wiley InterScience (www.interscience.wiley.com).

VVC 2008 Society of Plastics Engineers

POLYMER COMPOSITES—-2008

conformation of three methylene groups of PTT [17–20],

the improvement of thermal properties through the incor-

poration of POSS into the PTT main chain will expand

the application fields of PTT dramatically.

EXPERIMENTAL PROCEDURES

Materials

Dimethyl terephthalate (DMT) and 1,3-propanediol

(PDO) were kindly supplied by the Huvis, Korea. Tetrai-

sopropyl titanate (TiPT), trifluoroacetic acid (TFA), and

phenol were purchased from Sigma-Aldrich, USA.

1,1,2,2-tetracholoroethane (TCE), dichloromethane (DCM),

and tetrahydrofuran (THF) were purchased from Samchun

Chemical, Korea and PDIB–POSS was purchased from

Hybrid Plastics, USA. All these chemicals were used as

received.

Preparation of PTT–POSS Nanocomposites

The PDIB–POSS is well dispersed in PDO using ball

milling and the mixture of DMT, PDO, and PDIB–POSS

was charged in the autoclave with a 1:0.995:0.005 to

1:0.98:0.02 molar ratios followed by adding TiPT as a cat-

alyst (�75 ppm of the amount of DMT) and excess PDO

(1.2 mol). The reaction mixture was heated to 2208C with

stirring under a mild stream of nitrogen for an ester-inter-

change reaction to occur. During this reaction, more than

95% of methanol to be released theoretically was removed

and bis-hydroxypropyl terephthalate was formed in the re-

actor. The mixture was then heated to 2558C for 45 min

with a gradual reduction of pressure to less than 1 Torr in

the reactor upon controlled vacuuming to remove excess

PDO. Polycondensation reaction was carried out for further

3 h with a continuous removal of the by-product, PDO, in-

vacuo. After the completion of the polycondensation step,

the PTT–POSS nanocomposites were extruded out in the

form of spaghetti in an iced water bath. The spaghettis

were cut into small chips and purified to remove unreacted

POSS by Soxhlet extraction with THF for 3 days. The syn-

thesis reaction of PTT–POSS nanocomposites can be sum-

marized as in Scheme 1. The sample was coded as PTT–

POSS-#. #, where #. # represents the mole percentage of

PDIB–POSS fed initially.

Characterization

The solubility of resultant products was assessed using

various solvent systems containing phenol, TFA, TCE,

and DCM. The intrinsic viscosity of the synthesized

SCHEME 1. Overall synthesis reaction of PTT–POSS nanocomposites.

DOI 10.1002/pc POLYMER COMPOSITES—-2008 895

PTT–POSS sample was measured using a thermostatically

controlled Schott AVS 260 auto viscometer with an initial

sample concentration of c ¼ 1.5 g/dL at 208C and the

mixture of phenol-TCE (1:1 w/w) as a solvent. Fourier

transform infrared (FTIR) spectra were measured with a

Bruker 66 V FTIR instrument. The 1H NMR spectra were

recorded with a Joel JNM-AL300 (300 MHz) spectrome-

ter using �5 wt% solution of PTT–POSS in CDCl3/TFA

(40/60 v/v). The POSS content of the resultant nanocom-

posites were also evaluated with a Perkin–Elmer ICP–

OES (Optima 5300DV) using the nitric acid digested

extract of PTT–POSS. The differential scanning calorime-

try (DSC) was performed from �20 to 2508C with a

Thermal Analysis DSC Q1000 instrument. Thermogravi-

metric analysis (TGA) was performed from room temper-

ature to 6008C with a thermal analysis TGA-2050

thermogravimetric analyzer. Both DSC and TGA mea-

surements were performed at a 108C/min scanning rate

under N2 atmosphere.

The X-ray powder patterns of purified PTT–POSS

nanocomposites and neat PDIB–POSS were obtained

through equatorial scanning in the reflection mode with

Cu Ka radiation on an MXP18 diffractometer (MAC Sci-

ence, Japan). The X-ray diffraction (XRD) scans of as-

polymerized PTT–POSS films were also obtained with Cu

Ka radiation in the transmission 2D mode on a D8 DIS-

COVER diffractometer equipped with GADDS system

(Bruker AXS, Germany). The micrographs of the frac-

tured surfaces of the PTT–POSS samples were obtained

using a Leica Cambridge scanning electron microscope

(SEM, Stereoscan 440). The dynamic mechanical thermal

analysis was carried out with a Seiko DMS210 dynamic

mechanical analyzer in a tensile mode with a rectangular

sample (20/5 mm, length/width) from 15 to 2008C at a

rate of 28C/min and a frequency of 1 Hz. Using a Mini

max molder (BAU Tek, Korea), the PTT–POSS chips

melted at 2608C for 5 min were extruded into a mold

maintained at 1308C, cooled to room temperature and

dog-bone shaped specimen were obtained for tensile

measurements. Tensile modulus, tensile strength, and

elongation at break were evaluated using an INSTRON

model 4480 testing machine with a cross-head speed of

10 mm/min under standard condition (238C, RH: 65%).

All the values reported are an average of at least five

measurements.

RESULTS AND DISCUSSION

Confirmation of the Synthesis of PTT–POSS Copolymerand Copolymerization Yield

The chemical structure of the purified PTT–POSS

nanocomposites was examined with both FTIR and 1H

NMR spectroscopies. In the FTIR spectrum (Fig. 1A), the

increase in the C��H stretching of methylene group with

an increase in the content of POSS was clearly observed

at the peak position at 2,958 cm�1. Moreover, the addi-

tion of POSS also influences the doublet peak observed at

the center of 1,115 cm�1, corresponding to the C��O

stretching of alcohol part of ester group. This doublet

overlaps with the peak at 1,105 cm�1 assigned to the

Si��O stretching of the POSS. Thus the absorbance of the

doublet is increased with an increase in the content of

POSS as shown in Fig. 1B, which clearly indicates the

successful incorporation of POSS in the PTT main chain

[10, 11, 21, 22].

Figure 2 presents the 1H NMR spectrum of purified

PTT–POSS-2.0 nanocomposite. The isobutyl moieties of

PDIB–POSS units show three peaks at d ¼ 0.70 ppm

(��Si��CH2), d ¼ 1.04 ppm (��CH��(CH3)2), and d ¼1.95 ppm (��Si��CH2��CH) [10, 22]. The peak corre-

sponding to the methylene protons of PTT segments were

observed at d ¼ 2.46 ppm (O��CH2��CH2) and d ¼ 4.7

ppm (��O��CH2) [10, 22]. The aromatic protons of PTT

segments were observed at d ¼ 8.23 ppm [23]. Hence,

from the results of FTIR and 1H NMR of purified PTT–

POSS nanocomposites, one can confirm the chemical

structure of PTT–POSS nanocomposites as shown in

Scheme 1. Further, the mole fraction and weight fraction

of POSS in the resultant nanocomposites can be obtained

from Eqs. 1 and 2, respectively, using the area of methyl-

ene protons of PDO segments appearing in the ranges of

d ¼ 2.4–2.6 ppm and d ¼ 4.62–4.83 ppm and the area of

FIG. 1. FTIR spectra of PTT–POSS nanocomposites (A) 3,000–2,800 cm�1; (B) 1,800–600 cm�1.

896 POLYMER COMPOSITES—-2008 DOI 10.1002/pc

the isobutyl peaks of PDIB–POSS appearing in the range

of d ¼ 0.98–1.94 ppm. The copolymerization yield% of

PDIB–POSS was obtained from Eq. 3.

Mole fraction of POSS ¼A1:04ppm=42

A1:04ppm=42� �þ ðA2:46ppm þ A4:7ppmÞ=6

� � ð1Þ

FIG. 2. 1H NMR spectrum of PTT–POSS-2.0.

TABLE 1. Composition of PDIB-POSS in the PTT-POSS nanocomposites.

Sample codes

PDO:PDIB–POSS

feed ratio (mol%)

PDO:PDIB–POSS

ratio in as-

polymerized

samples (mol%)

PDO:PDIB–POSS

ratio in purified

samples (mol%)

Yield (%)

(purified

samples)

PTT-POSS-0.5 99.5:0.5 99.67:0.33 99.79:0.21 42.58

PTT-POSS-1.0 99.0:1.0 99.39:0.61 99.48:0.52 52.23

PTT-POSS-1.5 98.5:1.5 99.03:0.97 99.12:0.88 58.58

PTT-POSS-2.0 98.0:2.0 97.41:1.59 97.86:1.14 57.01

:

wt % of POSS ¼Mole fract. of POSS�M:W of POSS

Mole fract. of POSS�M:W of POSSþ ð1�mole fract. of POSSÞ �M:W of PTT repeating unit� 100 ð2Þ

Yield ð%Þ ¼ wt % of POSS in purified sample

Feed wt% of POSS� 100

(3)

The results were summarized in Table 1 and it confirms

that nearly 57% of POSS fed initially was successfully

incorporated into the PTT main chain. To further confirm

the incorporation of POSS, the resultant PTT–POSS nano-

composites were subjected to the elemental analysis using

ICP–OES, in which the linearized increase in the content

of Si with an increase in the content of POSS was

observed. Neat PTT, PTT–POSS-0.5, -1.0, -1.5, and -2.0

showed Si content of 0.0, 0.2160, 0.4780, 0.5910, 1.1000

wt%, respectively. The amount of unreacted POSS in the

sample can also be evaluated from the 1H NMR spectra

of unpurified PTT–POSS nanocomposites (Table 1).

Solubility and Molecular Weight

The neat PTT and PTT–POSS nanocomposites were

readily soluble in TFA and TFA/DCM (1:1 v/v) mixture.


PTT–POSS-0.5, -1.0, and -1.5 were soluble in phenol/

TCE mixture (1:1 w/w) at 608C under constant stirring,

whereas the PTT–POSS-2.0 is comparatively less soluble

in phenol/TCE mixture. This may be due to the presence

of physical cross-linking or aggregation behavior of

PDIB–POSS incorporated in the nanocomposites [22].

Since TFA and the TFA/DCM mixture are volatile in na-

ture, the phenol/TCE mixture was used as a solvent for

the measurement of intrinsic viscosity (IV) of the PTT–

POSS nanocomposites. The IV is increased for PTT–

POSS-0.5 (Z ¼ 1.1067) and then decreased for PTT–

POSS-1.0 and -1.5 (Z ¼ 0.8914 and 0.8332). However,

the intrinsic viscosity of the nanocomposites was not

reduced below that of neat PTT (Z ¼ 0.7358). The IV of

PTT–POSS-2.0 could not be measured due to its less sol-

ubility in phenol/TCE mixture solvent. Although the mag-

nitude of IV is widely used in evaluating the average

molecular weight of synthesized polymer product, it can

be wrong to compare the average molecular weights of

the homopolymer and its copolymer using only the IV

data, because the homopolymer and its copolymer have

quite different solution properties because of different

chain conformational statistics caused by the chemical

composition differences [11]. The increase in the IV of

PTT–POSS-0.5 may be due to either increase in the aver-

age molecular weight or the presence of micro or nanoag-

gregates of POSS in the polymer solution [9, 24]. On the

other hand, the decrease in IV of PTT–POSS-1.0 and -1.5

may suggest that the presence of aliphatic diols could

lead to incorporation of PDIB–POSS as a pendent or end

group rather than a chain extension agent [14].

Morphology

Figure 3 presents the typical SEM micrographs of the

fractured surface of the neat PTT and PTT–POSS-1.5.

Most of the POSS molecules were uniformly distributed

in PTT matrix. It is obvious that there is no phase separa-

tion with relatively less POSS loadings used in this study.

The surface roughness was increased with an increase in

the content of POSS. The observed results reflect the fact

that, with a careful choice of the functional groups, POSS

can be dispersed in the polymer matrices at molecular

level [14] whereas, relatively less dispersion of POSS

molecules was achieved through melt compounding

regardless of the types of POSS [9, 14, 15]. The POSS

molecules with the functional groups can give better dis-

persion results than its nonreactive counterparts, espe-

cially through in situ polymerization.

Crystal Structure

To predict the effect of the PDIB–POSS on the crystal

structure of the resultant nanocomposites, XRD scans of

PTT–POSS nanocomposites were performed before and

after purification process. The neat PDIB–POSS was also

subjected to the XRD measurements to ascertain its posi-

tion in the nanocomposites. As shown in Fig. 4A, the

XRD patterns of the unpurified PTT–POSS nanocompo-

sites showed the crystalline peaks at 2y values of 15.68,16.98, 19.768, 21.58, 23.628, 24.958, and 27.98 which

were related to the (010), (0112), (012), (110)/(100),

(112)/(103)/(102), (113), and (103) reflection planes of tri-

clinic PTT crystal, respectively [25–30]. The unpurified

PTT showed the diffused diffraction halo similar to that

appearing in amorphous polymers, because, the sample

used for X-ray measurement was previously melt-

quenched under liquid nitrogen. In addition to the crystal-

line peaks of PTT, a broad crystalline peak associated

with PDIB–POSS was also observed at 2y ¼ 8.268, whichis the common peak usually exhibited by the POSS hav-

ing the cyclopentyl, cyclohexyl, and isobutyl groups [9,

11, 12, 31]. The relative intensity of the POSS peak was

found to be increased with the increased amount of

POSS. This effect was well pronounced especially in

PTT–POSS-1.5 because of crystalline aggregates of

unreacted POSS in the PTT matrix.

FIG. 3. SEM images of fractured surface of (A) neat PTT and (B) PTT–POSS-1.5.


Figure 4B shows the X-ray powder patterns of the neat

PDIB–POSS, purified neat PTT, and purified PTT–POSS

nanocomposites. The neat PDIB–POSS exhibits the crys-

talline peaks at the 2y values 8.268, 11.088, 12.288, and19.268. When compared with the unpurified ones, nearly

same trend in crystalline peaks associated with the PTT

was observed. However, two significant changes are

observed after purification. One is that the crystalline

peaks became sharper and the peak observed around 2y ¼21.58 was getting disappeared. This change may be asso-

ciated with lamella thickening caused by annealing effect

and increased crystallinity through solvent-induced crys-

tallization in the course of purification with THF. The

other significant change is that the diffraction peak related

with the PDIB–POSS almost disappeared in purified

PTT–POSS nanocomposite samples. This suggests that

the POSS molecules incorporated into the PTT main

chain cannot form so large aggregates which can form

crystalline domains and is also confirmed from the previ-

ous reports related to the synthesis and characterization of

the polymer-POSS nanocomposites. When the POSS mol-

ecules exist as either pendent group (in side chains) or

end group of the host polymer chain, they aggregate to

form crystalline domains resulting in their characteristic

crystalline peaks. [9, 11, 12, 15, 31]. Therefore, the trend

observed in the XRD patterns of purified PTT–POSS-0.5

to -1.5 samples suggests that the unreacted POSS mole-

cules should be removed during the purification process

and most of the POSS molecules incorporated into the

PTT main chain should be located randomly in the PTT–

POSS copolymer [11]. However, the appearance of POSS

peak with weak intensity in the PTT–POSS-2.0 may also

suggest that some of POSS molecules could also be

located as either pendent or end group of the PTT main

chain.

Thermal Transition Behavior and Resistanceto Thermal Degradation

The amorphous film of neat PTT and PTT–POSS

nanocomposites were prepared through melt-quenching

into liquid nitrogen and subjected to the DSC studies to

facilitate clear observation of cold-crystallization behavior

as well as glass transition. Figure 5A shows the first heat-

ing curve of PTT–POSS nanocomposites, in which the

glass transition temperature (Tg) and cold-crystallization

temperature (Tcc) were decreased with an increase in the

content of POSS, except PTT-POSS-0.5. A slight depres-

sion in the Tg and Tcc was observed with an increase in

the POSS content. This suggests that the presence of

POSS cages incorporated in the PTT main chain should

reduce the intermolecular interaction between the PTT

chains and play an inert diluent role to decrease the self

association interaction force of polymers, leading to the

FIG. 4. XRD patterns of (A) unpurified; (B) purified PTT–POSS nanocomposites.

FIG. 5. (A) DSC thermogram of PTT–POSS nanocomposites (First heating); (B) Loss tan d versus temper-

ature for PTT–POSS nanocomposites.


depression in Tg [10, 13, 22]. On the other hand, the

depression in Tg and Tcc also results from the internal

plasticizing action of unreacted POSS, if any [15]. Since

the increase in the chain mobility because of the depres-

sion in Tg makes the amorphous chain diffuse more easily

into the crystal phase, cold-crystallization, where the dif-

fusion controlled crystallization is much more dominant

than nucleation controlled melt-crystallization, can be

observed at a little lower temperature as shown in Fig.

5A. The Tg, Tcc, and Tm data of PTT-POSS nanocompo-

sites were summarized in Table 2.

The cooling curves (Figure not shown here) showed

the decrease in melt crystallization temperature (Tcm)shifts to lower temperature with an increase in POSS con-

tent except PTT–POSS-0.5 sample (Table 2). The depres-

sion in Tcm may be due to the chain irregularities and

shortening of the crystallizable PTT chain length caused

by the randomly copolymerized PDIB–POSS. On the

other hand, there may be a possibility of the presence of

physical cross-linking between the nonpolar POSS seg-

ments as observed in the solubility test, which can also

reduce the movement of crystallizable PTT. The XRD

results also suggest the possibility of the presence of

physical crosslinking, which can lead to the formation of

crystalline aggregates. The second heating curves (figure

not shown here) showed nearly the same trends of Tm as

observed in the first heating (Table 2). The slight decrease

in the Tm may also have resulted from the reduction in

the crystallizable PTT chain length with an increase in

the content of POSS, resulting in thinner lamellar crystal.

The trends observed for Tg in DSC studies were further

confirmed by the DMTA measurements. Generally, the

primary a-relaxation is considered as a corresponding fac-

tor for the glass transition [32, 33]. As seen in Fig. 5B,

the tan d value of the a- relaxations tells the gradual

depression of Tg with an increase in the content of POSS.

The neat PTT and both PTT–POSS-0.5 and -1.0 show the

glass transition at 45 and 428C, respectively and PTT–

POSS-1.0 and -2.0 samples exhibit the glass transition in

the temperature range of 398C.The thermogravimetric plots of PDIB–POSS macro-

mer, neat PTT, and PTT–POSS nanocomposites are

shown in Fig. 6. The TGA curves show no significant

weight loss below 1008C, indicating that the samples

were completely anhydrous [34]. The observed weight

loss trends due to the decomposition of PTT and PTT–

POSS hybrids are found to be similar throughout the deg-

radation range observed. However, the amount of residue

seems to be increased with an increase in the content of

POSS. No significant improvement in the thermal stability

of PTT–POSS nanocomposite may be attributed to less

thermal stability of PDIB–POSS itself. The PDIB–POSS

starts to decompose at around 1508C and then the weight

loss is pronounced at around 2508C. PDIB–POSS exhibits

nearly 80% weight loss at 3258C, whereas the neat PTT

and PTT–POSS nanocomposites show the 80% weight

loss up to 4208C. The less thermal stability of PDIB–

POSS may associate with its sublimation behavior at

lower temperatures [3, 21, 35].

TABLE 2. Thermal properties of PTT-POSS nanocomposites.

Sample code

Glass

transition

temperature

(Tg, 8C)

Cold

crystallization

temperature (Tcc, 8C)

Melt

crystallization

temperature

(Tcm, 8C)

Melting point (Tm, 8C)

In first

heating

In second

heating

Neat PTT 47.45 64.87 193.12 225.6 226.5

PTT-POSS-0.5 50.77 69.68 193.93 226.7 226.4

PTT-POSS-1.0 44.43 64.80 188.72 225.2 224.9

PTT-POSS-1.5 43.61 64.10 177.47 223.3 221.8

PTT-POSS-2.0 41.42 59.43 179.47 222.0 222.2

FIG. 6. TGA curves of PDIB–POSS and PTT–POSS nanocompositess.

TABLE 3. Mechanical properties of PTT-POSS nanocomposites.

Sample codes

Initial modulus

(MPa)

Strength at break

(MPa)

Elongation at

break (%)

PTT Control 785.43 50.98 232.767

PTT-POSS-0.5 783.67 39.50 5.006

PTT-POSS-1.0 667.20 30.72 4.565

PTT-POSS-1.5 582.67 17.82 3.304

PTT-POSS-2.0 490.13 15.71 3.445


Mechanical Properties

Table 3 lists the initial modulus, breaking strength, and

elongation (at break) values of PTT–POSS nanocomposites.

When compared with the neat PTT, most of these mechani-

cal properties are decreased with an increase in the content

of PDIB–POSS. The drastic decreases in the initial modu-

lus and breaking strength are due to reduction in crystallin-

ity and lamellar thickness and crystalline defects caused by

the reduction in the intermolecular attraction between the

PTT chains and PTT sequence length by the incorporation

of PDIB–POSS into the PTT main chain. Moreover, break-

ing strain was also decreased drastically like initial modu-

lus and breaking strength, which suggests that the inter-

facial adhesion between POSS and PTT should be less,

resulting in the formation of voids during the test.

CONCLUSION

The PTT–POSS nanocomposites were successfully syn-

thesized through in situ polymerization method. The

incorporation of 1,2-propanediolisobutyl-POSS (PDIB–

POSS) in PTT was identified and confirmed by FTIR

spectroscopy and elemental analysis (ICP–OES). The

structure of the nanocomposites and the amount of PDIB–

POSS incorporated in PTT were assessed by 1H NMR

spectroscopy. The SEM images showed the nanoscaled

even distribution of POSS in the PTT matrix. XRD pat-

terns showed the crystal structure and position of POSS

in the PTT–POSS nanocomposite. The DSC results

showed decreases in glass transition, cold crystallization

temperature, and melting temperature of PTT–POSS

nanocomposites with an increase in the content of POSS.

The addition of PDIB–POSS does not show any signifi-

cant improvements in the thermal stability. On the other

hand, the mechanical properties such as initial modulus,

breaking strength, and elongation at break were decreased

with an increase in the content of POSS.

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