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Synthetic Metals 175 (2013) 112– 119

Contents lists available at SciVerse ScienceDirect

Synthetic Metals

journa l h om epa ge: www.elsev ier .com/ locate /synmet

ybrid organic–inorganic nanocomposite: Fluorinatedoly-(2,5-thienylbenzobisoxazole)/POSS and its properties

uang Yang, Zhaojun Xue, Qixin Zhuang, Xiaoyun Liu ∗, Kan Zhang, Zhewen Haney Laboratory for Specially Functional Polymeric Materials and Related Technology of the Ministry of Education, East China University of Science and Technology,hanghai 200237, China

a r t i c l e i n f o

rticle history:eceived 30 October 2012eceived in revised form 10 March 2013ccepted 9 May 2013vailable online 7 June 2013

a b s t r a c t

This article reports the in situ preparation of fluorinated poly-(2,5-thienylbenzobisoxazole)/polyhedraloligomeric silsesquioxane (6FPBOT/POSS) nanocomposites and their chemical and physical properties.POSS participated in the polymerization reaction and thus led to the homogenous dispersion of POSSnanoparticles in the 6FPBOT matrix. The structures and morphology of the obtained nanocomposites werefully characterized by Fourier transform infrared spectroscopy, wide-angle X-ray scattering, thermogravi-

eywords:FPBOTOSSanocompositesechanical propertiesielectric properties

metric analysis, and transmission electron microscopy. The nanocomposites exhibited excellent thermalstability. The introduction of POSS evidently increased the mechanical properties (tensile strength andtensile modulus) of the nanocomposites and significantly enhanced the quantum yield of 6FPBOT byreducing the degree of interchain aggregation. The dielectric constants of the nanocomposites decreasedwith increasing POSS content. The dielectric constant of the materials decreased from 2.56 for the 6FPBOTto 2.11 for the 6FPBOT–POSS nanocomposite with 5% POSS.

. Introduction

Organic–inorganic hybrid nanocomposites have been recentlysed in the electronics, aerospace, and automobile industries1,2]. The preparation of organic/inorganic polymer hybrids athe nanometer level has recently attracted much attention. Theovel method combining inorganic chemistry and organic chem-

stry produces hybrid materials with excellent performance [3].he performance was between the traditional organic and inor-anic materials, exhibiting superior processability, toughness, andow cost of organic materials, while preserving the heat resistance,xcellent oxidation, and mechanical properties of inorganic mate-ials. This combined method has already become a key vehicleor preparing high-performance functional materials. One of the

ost recent approaches involved the incorporation of polyhedralligomeric silsesquioxane (POSS) into the conjugated polymer [4].OSS consisting of a silica cage surrounded by tunable organic sub-titution groups are hybrid organic–inorganic nanobuilding blocks.OSS are composed of organic/inorganic molecules, approximately

nm–3 nm in size, with the general formula (RSiO1,5)n, where R is

ydrogen or an organic group, such as alkyl, aryl, or any of theirerivatives (Scheme 1). Depending on their compatibility with the

∗ Corresponding author. Tel.: +86 21 64252464.E-mail address: liuxiaoyun@ecust.edu.cn (X. Liu).

379-6779/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.synthmet.2013.05.006

© 2013 Elsevier B.V. All rights reserved.

polymer matrix, POSS moieties could either disperse almost withina molecular level or aggregate into nanoscale domains [5].

Conjugated rigid-rod polybenzobisazoles are a type of high-performance polymer with robust high-temperature resistance,photochemical and electrochemical stability, n-type dopability,and solution processability [6,7]. Wang et al. [6,8,9] has mademuch work on the photophysical properties of polybenzobisazoles.Thiophene-based systems were investigated to reduce the bandgap because of their stability and structural versatility. The photo-luminescence properties of PBOT attracted our attention becausethe emitting color can be adjusted by changing the content of thenarrow band gap, electron-donating thiophene ring based on theenergy-transfer principle, considering the benzobisoxazole moietyis an electron acceptor. [8,10] Thiophene-based benzobisoxazolemodel compounds were found to enhance third-order optical sus-ceptibility [8,11].

Considering the bulky volume and, more importantly, the self-assembly of POSS in the polymer matrix, POSS dispersed on thenanoscale often exhibits high thermal stability, high solvent resis-tance, increased modulus, improved quantum yield, and reduceddielectric constant. Introducing POSS into conjugated polymerscould be a novel and effective way of constructing conjugated mate-rials with optoelectronic properties comparable with dendronized

or grafted conjugated polymers. Some experimental studies onhybrid materials-based POSS were also proposed and investigated,such as the synthesis of a POSS-polyfluorene hybrid series exhibit-ing a higher PL quantum yield [12–14]. The significantly enhanced

G. Yang et al. / Synthetic Metal

eo

monpdeot

ztdhwctiati

2

2

2ofC

2

p(

Scheme 1. The chemical structure of POSS.

lectroluminescent characteristics were attributed to the reductionf aggregate/excimers [6,8,9,15,16].

A previous study reported that pure nanoporous POSS macro-olecules have a very low dielectric constant (1.8–2.7) because

f the nanoporosity of POSS molecules. Covalently combininganoporous POSS molecules with polyimide to form nanocom-osites was demonstrated as an effective way of reducing theielectric constant of polyimides without their mechanical prop-rties decreasing [17]. Vengatesan et al. synthesized a new typef polybenzoxazine (PBZ)–POSS hybrid nanocomposites and foundhat the POSS-filled PBZ shows a low dielectric constant [18].

In this paper, a novel thiophene-based fluorinated polyben-obisoxazole (6FPBOT) was synthesized. The introduction ofrifluoromethyl group in polybenzobisoxazole could decrease theielectric constant of the polymers. [19] The inorganic–organicybrid of 6FPBOT–POSS nanocomposites is reported in the presentork. To the best of our knowledge, polybenzobisoxazole-POSS

omposites have not yet been explored in detail. The structures ofhe resulting composites were characterized by Fourier-transformnfrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD),nd transmission electron microscope (TEM). The photophysical,hermal, and dielectric properties of the composites were alsonvestigated.

. Experimental

.1. Materials

2,5-Thiophenedicarboxylic acid was purchased from Alfa Aesar.,2-Bis(3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP) wasbtained from commercial sources and dried under vacuum at 40 ◦Cor 24 h before use. Other reagents were obtained from Aldrichhemical Co. The reagents were of high purity and used as received.

.2. Preparing of 6FPBOT–POSS nanocomposites

The preparation of 6FPBOT–POSS nanocomposites wereerformed according to Scheme 2. In a reactor vessel, 1.72 g10 mmol) 2,5-thiophenedicarboxylic acid, 3.66 g (10 mmol) 6FAP,

s 175 (2013) 112– 119 113

a corresponding amount of POSS, 60 g poly(phosphoric acid) (PPA),and 15 g phosphorus pentoxide (P2O5) were mixed under argon atroom temperature. The mixture was stirred at 60 ◦C until completedissolution was achieved. The following temperature profile wasused during polymerization: 110 ◦C for 10 h, followed by 150 ◦Cfor 10 h, 170 ◦C for 6 h, and then 190 ◦C for 4 h. The system wascooled to 60 ◦C and was poured into a large amount of water,thereby obtaining the polymer precipitate. The precipitate wasrepeatedly washed with hot water to remove the residual PPA andmonomers completely. The product was collected via filtrationand then dried under vacuum at 80 ◦C for 24 h. The compositeswere named 6FPBOT–POSSx, where x denotes the content of POSSin the composites. For example, 6FPBOT–POSS5 indicates that thePOSS content in the composite is 5%.

2.3. Characterization

The ultraviolet–visible (UV–vis) spectra of polymer/methane-sulfonic acid (MSA) solution and films were recorded on a VarianCary 500 UV–vis spectrophotometer at room temperature in arange of 200 nm–800 nm. Fourier transform infrared spectra (FTIR)were recorded on a Nicolet Magna-IR 550 FTIR spectrometeron potassium bromide (KBr) pellets. Thermogravimetric analysis(TGA) was performed on a Du Pont Model 951 in flowing nitro-gen at a heating rate of 10 ◦C min−1. The mechanical properties ofthe films (50 × 5 × 0.03 mm, length × width × thickness) were mea-sured with an Instron 4465 instrument in ambient atmosphere ata crosshead speed of 20 mm min−1. All reported results are theaverages of at least 30 specimens. Photoluminescence (PL) spec-tra of polymer/MSA solution and films were done with a VarianCary Eclipse fluorescence spectrophotometer at room tempera-ture. The dielectric properties were measured on Concept 40 broadband dielectric spectrometer (Novocontrol Technologies GmbH& Co. KG, Germany) at 1000 Hz as disk-shaped samples (20 mmin diameter, 1 mm in thickness). Thin films were fabricated byJenekhe’s method [20], spin-coating of the polymer solution innitromethane/AlCl3 with a polymer concentration of ∼3 wt.% ontosynthetic silica substrates for optical characterizations. The thinfilms were dried at 80 ◦C in a vacuum oven for 12 h after completedecomplexation in deionized water. Solid 29Si NMR spectrum wasmeasured using a Bruker Avance DRX-500 (500 MHz) spectrom-eter with tetramethylsilane as the standard. Measurement of theabsolute PL efficiency was performed on LabsphereIS-080, whichcontained an integrating sphere coated on the inside with a reflect-ing material barium sulfate. PL efficiency was calculated from thesoftware attached by LabsphereIS-080.

3. Results and discussion

3.1. Chemical structure of the PBOT–POSS nanocomposites

Fig. 1 presents the FTIR spectra of the 6FPBOT–POSS nanocom-posites. The FTIR spectrum of pristine POSS displayed two majorcharacteristic peaks located at approximately 1123 (Si O Sistretching) and 750 cm−1 (symmetric Si O Si band). The char-acteristic bands at 1625 (C N stretching) and 1024 cm−1 (C Ostretching) were attributed to the benzoxazole structures of6FPBOT [21–23]. The peaks at 1609, 1584, and 1565 cm−1 werethe characteristic bands of the aromatic ring. The characteristicpeak of the trifluoromethyl ( CF3) groups was at ∼1250 cm−1. The

peaks around 1122 and 790 cm−1 were the characteristic bands ofthiophene [24]. In Fig. 1, the characteristic peaks of POSS was notobserved. The characteristic peaks of POSS may be overlap with thecharacteristic peaks of thiophene group.

114 G. Yang et al. / Synthetic Metals 175 (2013) 112– 119

f 6FP

Fncg

[14,26]. As shown in Fig. 2, the result obtained was ∼100 ppm,

Scheme 2. Synthetic route o

The solid 29Si NMR spectrum of 6FPBOT–POSS1 is shown in

ig. 2. According to a previous study [4], the characteristic reso-ance for POSS was at ∼75 ppm. The phenyl group of the POSS andarboxylic acid monomers could undergo an F–C reaction [25]. Afterrafting the polymer chain, the POSS resonance shifted to ∼80 ppm

Fig. 1. FTIR spectra of 6FPBOT–POSS nanocomposites.

BOT–POSS nanocomposites.

which might be attributed to the strong electronegativity of thetrifluoromethyl ( CF3) group. The results are also direct evidencethat the 6FPBOT chains were successfully connected to the POSS

Fig. 2. Solid 29Si CP/MAS NMR spectra of 6FPBOT–POSS1.

G. Yang et al. / Synthetic Metals 175 (2013) 112– 119 115

vc

3

ua6iaaithibmlntdtMpiy

tflawi(

TT

has strong interchain interactions or forms crosslink networks, itcould constrain POSS to crystallize [13]. Thus, this 6FPBOT sys-

Fig. 3. TGA thermograms of 6FPBOT–POSS.

ia the connection between the phenyl groups in the POSS and thearboxylic acid groups in the 6FPBOT.

.2. Thermal stability of the 6FPBOT–POSS nanocomposites

The heat resistance of the composites was evaluated via TGAnder a nitrogen atmosphere (Fig. 3). The 5% weight loss (Td)nd the char yield at 700 ◦C are summarized in Table 1. TheFPBOT–POSS nanocomposties showed excellent thermal stabil-

ty. As shown in Fig. 3, the 5% weight loss for pure POSS wast approximately 450 ◦C. 6FPBOT showed good thermal stabilitynd a 5% weight loss at 520 ◦C. Remarkably, the thermal stabil-ties of all the 6FPBOT–POSS nanocomposites were higher thanhat of pure 6FPBOT and POSS. The possible reason is that theigh reactivity of POSS and its good miscibility with PBOT eas-

ly linked the POSS with the PBOT chain through strong covalentond and dispersed it uniformly in the composites. The POSSolecules acted as cross-linking sites for the PBOT chain. The

ow thermal conductivity of POSS due to its inorganic ceramicature and intrinsic nanoporous structure could hinder the heatransfer in the materials and effectively retard the thermal degra-ation of weak bonds embedded within the network. As a result,he thermal stability of the composite materials is enhanced [27].

oreover, POSS was heavily coated with 6FPBOT chains, whichrotected the POSS from thermal degradation. Hence, the compos-

tes with higher POSS content display significantly increased charield.

A previous study demonstrated that the distribution of POSS inhe hybrid material could affect the TGA curve [14]. The TGA curveuctuated at 450 ◦C if POSS did not disperse well in the matrix andggregated to form grains. Thus, considering that no fluctuationas observed in the curve, POSS was homogeneously dispersed

n this system in nanometer size within the 6FPBOT matrixFig. 3).

able 1hermal properties of 6FPBOT and 6FPBOT–POSS.

Sample Td(◦C) Char yield (700 ◦C) (%)

6FPBOT 508.9 73.56FPBOT–POSS1 526.6 74.56FPBOT–POSS2 527.1 78.36FPBOT–POSS5 527.7 79.8POSS 419.2 57.6

Fig. 4. WAXD patterns of pure POSS, 6FPBOT, and 6FPBOT–POSS nanocomposites.

3.3. Morphology of the PBOT–POSS composites

WAXD was used to examine the structure of the 6FPBOT–POSSnanocomposites. Fig. 4 shows the XRD curves of POSS, PBOT, and6FPBOT–POSS. The calculated results are listed in Table 2. Sharpdiffraction peaks for pure POSS appeared at 2� = 8.02◦ (an interpla-nar spacing of 1.11 nm), 11.0◦ (∼0.81 nm), 18.8◦ (∼0.48 nm), and25.0◦ (∼0.36 nm), indicating high crystallinity [28]. 6FPBOT showeda monoclinic crystalline structure [10]. The XRD patterns (Fig. 4)of pure 6FPBOT showed two major diffraction peaks at approxi-mately 2� = 15.6◦ (∼0.57 nm, peak A) and 23.4◦ (∼0.39 nm, peakB). The periodicities for peaks A and B represent the “side-by-side” distance ((2 0 0) plane) and “face-to-face” distance ((0 1 0)plane) between two neighboring polymer chains, respectively.Compared to 6FPBO, the “side-by-side” and “face-to-face” dis-tances of 6FPBO–POSS1 differed slightly, changing from 0.570 to0.566 nm and 0.39 to 0.378 nm, respectively; the “side-by-side”and “face-to-face” distances of 6FPBO–POSS5 change from from0.570 to 0.550 nm and 0.39 to 0.358 nm, respectively. It can beseen that both the interplanar distance and the size of orderedstructure of peak A and peak B are reduced with the introductionof POSS into the composites. This phenomenon could be ascribedto strong interaction between 6FPBOT and POSS. The diffractionpatterns of POSS, 6FPBOT, and 6FPBOT–POSS were compared. Theresults revealed that the nanocomposites did not exhibit typicalcrystalline structure features compared with pure POSS. Cough-lin et al. reported that the nature of the copolymer backbonesinto which POSS units are incorporated as pendant groups signifi-cantly affects POSS crystallization [29]. Many studies reported thatPOSS has a strong tendency to crystallize in composites becauseof the relatively high molarity [30–33]. However, if the polymer

tem has strong interchain interactions and can constrain POSS tocrystallize, which is similar to the system of dicyclopentadiene

Table 2X-ray results of 6FPBOT and 6FPBOT–POSS nanocomposites.

Sample 2� (◦) d (nm)

Peak A Peak B Peak A Peak B

6FPBOT 15.6 23.4 0.57 0.396FPBOT–POSS1 15.65 23.56 0.566 0.3786FPBOT–POSS2 15.96 24.02 0.555 0.376FPBOT–POSS5 16.11 24.90 0.550 0.358

116 G. Yang et al. / Synthetic Metals 175 (2013) 112– 119

; (b) 6

asww(

Fiorw

nCmd

3

c6u3tbctob[

Fig. 5. TEM of (a) 6FPBOT–POSS2

nd norbornenyethyl-POSS crosslinked copolymers, and polyimideide chain-tethered POSS nanocomposites [34]. In addition, POSSas well dispersed into the 6FPBOT matrix at the nanoscale level,hich was further confirmed by the TEM images of the composites

Fig. 5).Fig. 5 shows the TEM images of the 6FPBOT–POSS composites.

ig. 6 shows the SEM and EDS of the 6FPBOT–POSS1 nanocompos-tes. In Fig. 5, the darker points indicate POSS particles. The sizef POSS dispersed in 6FPBOT was 10-15 nm. These images clearlyevealed that no observable aggregation was formed and that POSSas well dispersed into the polymer matrix.

Fig. 7 presents photographs of the different 6FPBOT–POSSanocomposites. All samples showed excellent light transmittance.ombined with the information in Fig. 5, Fig. 7 concludes that noacrophase separation occurred between the 6FPBOT and POSS

omains in the nanocomposites.

.4. Mechanical properties of the 6FPBOT–POSS nanocomposites

The mechanical properties of the 6FPBOT and 6FPBOT–POSSomposite films are summarized in Table 3. Compared withFPBOT, the tensile modulus, tensile strength, and strain to fail-re of the 6FPBOT–POSS composite with 5 wt.% POSS increased to1%, 92%, and 27%, respectively. These findings could be attributedo two factors. First, the 6FPBOT chain movement was restrictedy the increasing cross-linking density of the materials as the POSSontent increased. Second, the increase in the hard segment con-

ent i.e., the POSS content also enhanced the mechanical propertiesf the hybrids.[32,33] The similar phenomenon was also reportedy Wang et al. in the polybenzazol/carbon nanotubes system.35,36]

Fig. 6. 6FPBOT–POSS1 nanocomp

FPBOT–POSS5 nanocomposites.

3.5. Photophysical properties of the 6FPBOT–POSSnanocomposites

In addition, an interesting phenomenon was found in thepresent study. Fig. 8 shows the UV spectra of the composites indilute MSA solution (0.44 mg dL−1) and in thin films. The normal-ized PL emission spectra of the composites in the MSA solutionand thin film are shown in Fig. 9. Relevant data are summarizedin Table 4. The UV peaks of conjugate 6FPBOT–POSS composites inthe MSA solution red-shifted compared with those in the thin film.However, the PL spectra of the polymer solution were almost thesame as that of the thin film.

UV absorption arose from the electron energy level transitionsof the molecules. The current analytical instruments were usu-ally extended to the visible or UV–vis region. The transitions couldbe divided into the following general categories: � → �*, � → �*,n → �*, and n → �* transitions. The energy required for a variety oftransitions was different. In general, the n → �* transition requiredminimum energy, and the absorption band appeared in the longwavelength region. Meanwhile, the n → �* and � → �* transi-tion absorption bands appeared in the short wavelength region,whereas the � → �* transition appeared in the far UV region. Themost important application of UV absorption spectrometry is deter-mining the situation of the conjugate in accordance with the � → �*transitions and energy levels.

In general, the UV absorption peaks for conjugated poly-mers in solution were the same as the UV absorption peaks

in the thin film, whereas the PL emission spectra of thethin film showed a large red-shift compared with that in thesolution. Bunz et al. studied the photophysics of poly[p-(2,5-didodecylphenylene)ethynylene] and found that the large red-shift

osite; (a) SEM and (b) EDS.

G. Yang et al. / Synthetic Metals 175 (2013) 112– 119 117

Fig. 7. Photographs of (a) 6FPBOT; (b) 6FPBOT–POSS1; (c) 6FPBOT–POSS2 and (d) 6FPBOT–POSS5 films.

Table 3Mechanical properties of the 6FPBOT and 6FPBOT–POSS nanocomposites.

6FPBOT 6FPBOT–POSS1 6FPBOT–POSS2 6FPBOT–POSS5

Tensile strength (MPa) 65 ± 7 77 ± 6 98 ± 9 125 ± 6Tensile modulus (GPa) 3.5 ± 0.2 3.7 ± 0.2 4.1 ± 0.1 4.6 ± 0.1Strain to failure (%) 2.3 ± 0.2 2.4 ± 0.3 2.7 ± 0.2 2.9 ± 0.3

d 6FP

(tesbw

i

Fig. 8. UV absorption spectra of pure POSS, 6FPBOT, an

approximately 50 nm) in the emission spectrum resulted fromhe planarization of the backbones rather than the formation oflectrical aggregates.[6,8,9,15,16,37,38] Meanwhile, the absorptionpectra did not show a significant red-shift [37]. This finding coulde attributed to the formation of a small portion of planar segments

ith extended effective conjugation in the solid state.

In our study, the possible reason of this interesting phenomenons the protonation effect of polybenzoxazole in MSA and the strong

Fig. 9. Photoluminescence spectra of pure POSS, 6FPBOT, and 6

BOT–POSS nanocomposites (a) in MSA, (b) thin films.

interchain interactions in thin film. In theory, the close packing inthe thin film causes the maximum absorption peak �max to red-shift compared with that in the solution. Thus, a strong electroncloud interaction resulted between the excited benzoxazole andthe other surrounding molecules. Meanwhile, the acids could pro-

tonate the nitrogen atoms of the benzoxazole and transform theneutral chains to polyelectrolytes. Protonation can stiffen poly-mer chains and facilitate aggregation, so protonation can affect the

FPBOT–POSS nanocomposites (a) in MSA, (b) in thin film.

118 G. Yang et al. / Synthetic Metals 175 (2013) 112– 119

Table 4Photophysical properties of 6FPBOT–POSS in the dilute MSA and thin film.

�max (UV, nm) �max (PL, nm) Quantum yield (film)

Solution Film Solution Film

6FPBOT 402(426) 380(337) 442(472) 447(475) 0.126FPBOT–POSS1 402(426) 376(345) 442(472) 446(474) 0.196FPBOT–POSS2 401(425) 377(322) 442(472) 445(474) 0.216FPBOT–POSS5 402(426) 376(324) 441(471) 445(474) 0.27

loss

eeTip

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3

nc

osnicMr

bccp

Fig. 10. (a) dielectric constant and (b) dielectric

nergy levels of the molecular orbital, which are believed to influ-nce the photo-electronic properties of polymers [15,16,38,39].herefore, the synergistic effect of the protonation and the strongnterchain interactions in the solid state made the emission peakositions in both the solution and thin film almost coincident.

The UV–vis and PL spectra of the 6FPBOT–POSS nanocompos-tes in MSA overlapped with that of pure 6FPBOT because noxcimer and exciplex formed in such a dilute solution. A similarehavior was also reported earlier by Wang [6]. Meanwhile, thebsorption and emission peaks of 6FPBOT–POSS in the thin filmas similar with that of pure 6FPBOT, whereas the intensity of

he emission peaks for the 6FPBOT–POSS nanocomposites weretronger than 6FPBOT in the thin film. Hence, the incorporationf the silsesquioxane core into 6FPBOT could improve the quan-um yield. This result may be attributed to the steric hindranceaused by the silsesquioxane core into 6FPBOT that suppressed theggregation of the 6FPBOT main chain. This occurrence is similaro a previously reported system of star-like polyfluorenes with ailsesquioxane core [34].

.6. Dielectric properties of 6FPBOT–POSS nanocomposites

Fig. 10 presents the dielectric properties of the 6FPBOT–POSSanocomposites. The introduction of POSS decreased the dielectriconstant.

The dielectric constant was directly related to the polarizabilityf the material and was thus strongly dependent on its chemicaltructure. Both the dielectric constants and the dielectric loss of theanocomposites decreased as the POSS content in the composites

ncreased. The possible reason is that the POSS of the cubic silicaore with homogeneous nanopores increased in the free volume.eanwhile, the POSS molecules have a lower polarity, which also

educed the dielectric constant and enhanced the dielectric loss.Pure nanoporous POSS has a very low dielectric constant

ecause of the nanoporosity of POSS molecules [40]. In addition,ovalently tethering nanoporous POSS to presynthesized polyimidehain ends or side chains results in organic–inorganic nanocom-osites with much lower dielectric constants [41]. Therefore, the

of 6FPBOT, and 6FPBOT–POSS nanocomposites.

6FPBOT–POSS nanocomposites can be used as low-dielectric mate-rials in microelectronic applications.

4. Conclusions

In this paper, a novel hybrid organic–inorganic conjugated poly-mer nanocomposites was successfully prepared in situ and named6FPBOT–POSS. The morphology, thermal stability, mechanicalproperties, photophysical properties, and dielectric properties ofthe nanocomposites were investigated in detail. The 6FPBOT–POSSnanocomposites exhibited excellent thermal stability and high dis-persity. The mechanical properties of the nanocomposites weregreatly improved compared with pure 6FPBOT. This particular6FPBOT–POSS molecular architecture significantly enhanced thequantum yield of 6FPBOT by reducing the degree of interchainaggregation. Meanwhile, the dielectric constants of the nanocom-posites decreased as the POSS content increased. The dielectricconstant of the 6FPBOT–POSS nanocomposite film decreased from2.56 for PBOT to 2.11 for 6FPBOT–POSS5.

Acknowledgements

The authors express their gratitude to the National NaturalScience Foundation of China (NSFC) for their financial support. Con-tract grant number is 50973028. This project is also supported bythe Shanghai Natural Science Foundation (12ZR1407900).

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