Conformational Disorder Within the Crystalline Region of Silica-Filled Polydimethylsiloxane:A Solid-State NMR Study  

作　　者：Yu-Qi Xiong Chang-Lin Li Ai Lu Liang-Bin Li Wei Chen 

机构地区：[1]National Synchrotron Radiation Laboratory,Anhui Provincial Engineering Laboratory of Advanced Functional Polymer Film,CAS Key Laboratory of Soft Matter Chemistry,University of Science and Technology of China,Hefei,230026,China [2]Department of Accelerator Science and Engineering Physics,School of Nuclear Science and Technology,University of Science and Technology of China,Hefei,230026,China [3]Institute of Chemical Materials,China Academy of Engineering Physics,Mianyang,621900,China

出　　处：《Chinese Journal of Polymer Science》2024年第11期1780-1792,I0012,共14页高分子科学（英文版）

基　　金：financially supported by NSAF Joint Fund of China(No.U2030203);the National Natural Science Foundation of China(Nos.51973207 and 51903230)。

摘　　要：The crystallization behavior of silica-filled polydimethylsiloxane(PDMS)was investigated in detail by^(1)H solid-state nuclear magnetic resonance(^(1)H SS-NMR)in combination with synchrotron radiation wide-angle X-ray scattering(WAXS),and temperature-modulated differential scanning calorimetry(TMDSC)techniques.For neat PDMS,no apparent difference is observed for the crystallinity characterized by^(1)H SS-NMR and WAXS at low-temperature regions.However,upon filler addition,a 15%-35%lower difference in crystallinity is observed measured by^(1)H SS-NMR compared to WAXS.The origin of such mismatch was explored through multi-component structural,dynamics,and chain-order analysis of PDMS samples with different filler fractions.The 1D integrated WAXS results of PDMS with different filler fractions at different temperatures show that the packing structure as well as crystal size basically remain unchanged,but as the filler fraction increases from 0 phr to 60 phr,the rigid component’s dynamics order parameter S_(r)obtained by^(1)H SS-NMR decreases from 0.70 to 0.55.The filler fraction-dependent crystallinity calculated based on S_(r)was compared with experimental values,revealing a behavior of decreasing order in the crystalline region.Combining with the results of accelerated chain dynamics in crystalline region as reflected by T_(2)values,the molecular origin is attributed to the formation of CONDIS crystals,whose conformational order is lost but the position and orientation orders are kept.Such hypothesis is further supported by the TMDSC results,where,as the filler fraction increases from 0 phr to 60 phr,the melting range widens from 8.77 K to 14.56 K,representing a growth of166%.In addition to previous reports related to the condition for forming CONDIS mesophase,i.e.,temperature,pressure,and stretching,the nano-sized filler could also introduce the local conformational disorder for chain packing.

关 键 词：Solid state NMR Polymer nanocomposite CONDIS crystal Local chain order PDMS crystallization 

分 类 号：TB332[一般工业技术—材料科学与工程]