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首页> 外文期刊>Journal of Applied Polymer Science >Polymer Dynamics in Rubbery Epoxy Networks/Polyhedral Oligomeric Silsesquioxanes Nanocomposites
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Polymer Dynamics in Rubbery Epoxy Networks/Polyhedral Oligomeric Silsesquioxanes Nanocomposites

机译：橡胶状环氧网络/多面体低聚倍半硅氧烷纳米复合材料中的聚合物动力学

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Dielectric techniques, including thermallystimulated depolarization currents (TSDC, -150 to 30°C)and, mainly, broadband dielectric relaxation spectroscopy(DRS, 10~(-2)- 10~6Hz, -150 to 150°C) were employed, nextto differential scanning calorimetry (DSC), to investigatemolecular dynamics in rubbery epoxy networks preparedfrom diglycidyl ether of Bisphenol A (DGEBA) and poly(oxypropylene)diamine (Jeffamine D2000, molecular mass2000) and modified with polyhedral oligomeric silses-quioxanes (POSS) units covalently bound to the chains asdangling blocks. Four relaxations were detected and ana-lyzed: in the order of increasing temperature at constantfrequency, two local, secondary γ and β relaxations in theglassy state, the segmental α relaxation associated with theglass transition and the normal mode relaxation, relatedwith the presence of a dipole moment component alongthe Jeffamine chain contour. Measurements on pure Jeff- amine D2000 helped to clarify the molecular origin of therelaxations observed. A significant reduction of the magni-tude and a slight acceleration of the α and of the normalmode relaxations were observed in the modified networks.These results suggest that a fraction of polymer is immobi-lized, probably at interfaces with FOSS, due to constraintsimposed by the covalently bound rigid nanoparticles,whereas the rest exhibits a slightly faster dynamics due toincreaseof free volume resulting from loosened molecularpacking of the chains (plasticization by the bulky POSSunits).The increase of free volume is rationalized by den-sity measurements.
机译：其次是采用电介质技术，包括热激励的去极化电流（TSDC，-150至30°C），主要采用宽带介质弛豫光谱法（DRS，10〜（-2）-10〜6Hz，-150至150°C）。差示扫描量热法（DSC），以研究由双酚A（DGEBA）的二缩水甘油醚和聚（氧化丙烯）二胺（Jeffamine D2000，分子质量2000）制备并用共价键合的多面体低聚硅烷-喹喔啉（POSS）单元改性的橡胶状环氧网络中的分子动力学到铁链悬空的块。检测并分析了四种弛豫：以恒定频率升高温度的顺序，在玻璃态下出现两个局部的，次级的γ和β弛豫，与玻璃化转变有关的分段α弛豫和与偶极子存在相关的正态弛豫Jeffamine链轮廓上的力矩分量。对纯Jeffamine D2000的测量有助于澄清观察到的松弛的分子起源。在修改后的网络中观察到了大幅度的减小，α的轻微加速和正模弛豫。这些结果表明，由于受到限制，聚合物的一部分被固定化了，可能在与FOSS的界面处共价键结合的刚性纳米颗粒，而其余部分则由于链的分子堆积松散（通过庞大的POSSunits塑化）而导致的自由体积增加而表现出更快的动力学。自由密度的增加通过密度测量来合理化。

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