A novel fluoro-terminated hyperbranched poly(phenylene oxide) (FHPPO): synthesis, characterization, and application in low-k epoxy materials
作者:Lijuan Luo、Teng Qiu、Yan Meng、Longhai Guo、Jing Yang、Zhuoxin Li、Xingzhong Cao、Xiaoyu Li
DOI:10.1039/c3ra40721g
日期:——
A new AB2 monomer 4-hydroxyl-4′,4′′-difluorotriphenylmethane was successfully synthesized via a Friedel–Crafts alkylation of phenol from 4,4′-difluorodiphenylmethanol. Based on the AB2 monomer, novel fluoro-terminated hyperbranched poly(phenylene oxide)s (FHPPOs) were synthesized via the SNAr reaction by self-condensation in one step. The FHPPOs were characterized by various techniques, including NMR, FT-IR, GPC, TGA and DSC. It was found that the molecular weight and polydispersity index of the FHPPOs increased with monomer concentration and reaction time. The degree of branching of the FHPPOs, determined by 13C NMR and 19F NMR with the aid of model compounds, decreased from 0.63 to 0.53 as the molecular weight increased. The glass transition temperature (Tg) of the FHPPOs increased with increasing molecular weight, up to 164 °C when the Mn was over 6, 800. The FHPPOs showed excellent thermal stability up to a Td5 temperature of 559 °C. Because of the low polarity of the poly(phenyl oxide) (PPO) backbones, abundant fluoro-terminated groups, which have large molar free volume, low polarizability of C–F bonds, and inherent free volume or molecule-scale cavities in hyperbranched structures, the addition of FHPPO into diglycidyl ether of bisphenol A (DGEBA) could effectively lower the relative dielectric constant, the dissipation factor, and moisture absorption of the cured DGEBA/FHPPO composites. The free volume of the composites, which was quantified by positron annihilation lifetime spectroscopy (PALS), increased with increased FHPPO loading. The excellent dielectric and thermal properties make FHPPO a promising low-k modifier for epoxy resins.
以4,4'-二氟二苯甲醇为原料,通过傅克烷基化苯酚,成功合成了新型AB2单体4-羟基-4',4''-二氟三苯甲烷。以AB2单体为基础,通过SNAr反应一步自缩合合成了新型氟封端超支化聚苯醚(FHPPOs)。 FHPPO 通过各种技术进行表征,包括 NMR、FT-IR、GPC、TGA 和 DSC。研究发现,FHPPO 的分子量和多分散指数随着单体浓度和反应时间的增加而增加。随着分子量的增加,FHPPO 的支化度(通过 13C NMR 和 19F NMR 借助模型化合物测定)从 0.63 降低至 0.53。 FHPPO 的玻璃化转变温度 (Tg) 随着分子量的增加而增加,当 Mn 超过 6, 800 时,玻璃化转变温度 (Tg) 高达 164 °C。FHPPO 在 Td5 温度高达 559 °C 时表现出优异的热稳定性。由于聚苯醚(PPO)主链的低极性,丰富的氟封端基团,具有大的摩尔自由体积、C-F键的低极化性以及超支化结构中固有的自由体积或分子级空腔结果表明,将FHPPO添加到双酚A二缩水甘油醚(DGEBA)中可以有效降低固化后的DGEBA/FHPPO复合材料的相对介电常数、损耗因数和吸湿率。复合材料的自由体积通过正电子湮灭寿命光谱 (PALS) 进行量化,随着 FHPPO 负载量的增加而增加。优异的介电和热性能使 FHPPO 成为一种很有前途的环氧树脂低 k 改性剂。