Hampu Nicholas, Hillmyer Marc A
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States.
ACS Macro Lett. 2020 Mar 17;9(3):382-388. doi: 10.1021/acsmacrolett.0c00036. Epub 2020 Feb 26.
A series of symmetric poly(methyl methacrylate--styrene)--polylactide (P(MMA--S)--PLA) diblock terpolymers with nearly constant molar masses yet varying block interaction parameters were synthesized as a model system to probe the extent and utility of composition fluctuations in the disordered state. A combination of differential scanning calorimetry, dynamic mechanical analysis, and small-angle X-ray scattering revealed that a broad range of segregation strengths ranging from what we ascribe to essentially a mean-field disordered to a fluctuating disordered to an ordered system could be readily obtained by tuning the molar fraction of styrene in these diblocks. The P(MMA--S)--PLA diblocks were annealed above their order-disorder transition temperatures () and rapidly quenched to low temperatures to trap the disordered state via vitrification, as confirmed by scanning electron microscopy. Small-angle X-ray scattering and N sorption analysis post-removal of PLA demonstrated that a transition from a very weakly structured, mean-field-like melt to a bicontinuous fluctuating disordered state occurred with increasing segregation strength. This work demonstrates that the extent of microphase segregation as well as the domain continuity of the disordered block polymer melt can be tuned using both synthetic design and thermal stimuli, guiding the design of disordered block polymers with targeted nanostructures that have potential technological utility.
合成了一系列具有近乎恒定摩尔质量但嵌段相互作用参数不同的对称聚（甲基丙烯酸甲酯-苯乙烯）-聚丙交酯（P（MMA-S）-PLA）二嵌段三元共聚物，作为一个模型系统来探究无序状态下组成波动的程度和效用。差示扫描量热法、动态力学分析和小角X射线散射相结合的结果表明，通过调节这些二嵌段中苯乙烯的摩尔分数，可以很容易地获得从我们认为基本是平均场无序到波动无序再到有序体系的广泛的偏析强度范围。通过扫描电子显微镜证实，P（MMA-S）-PLA二嵌段在其有序-无序转变温度以上进行退火，然后快速淬火至低温，以通过玻璃化转变来捕获无序状态。去除PLA后的小角X射线散射和N吸附分析表明，随着偏析强度的增加，发生了从结构非常弱的、类似平均场的熔体到双连续波动无序状态的转变。这项工作表明，使用合成设计和热刺激都可以调节微相分离的程度以及无序嵌段聚合物熔体的畴连续性，从而指导具有潜在技术效用的具有目标纳米结构的无序嵌段聚合物的设计。
