Multiblock copolymers (MBCPs) are an emerging class of materials that are becoming more accessible in recent years. However, to date there is still a lack of fundamental understanding of their physical properties. In particular, the glass transition temperature (T_g) which is known to be affected by the phase separation has not been well characterized experimentally. To this end, we report the first experimental study on the evolution of the T_gs and the corresponding phase separation of linear MBCPs with increasing number of blocks while keeping the overall degree of polymerization (DP) constant (DP = 200). Ethylene glycol methyl ether acrylate (EGMEA) and tert-butyl acrylate (tBA) were chosen as monomers for reversible addition–fragmentation chain transfer polymerization to synthesize MBCPs. We found the T_gs (as measured by differential scanning calorimetry) of EGMEA and tBA segments within the MCBPs to converge with increasing number of blocks and decreasing block length, correlating with the loss of the heterogeneity as observed from small-angle X-ray scattering (SAXS) analysis. The T_gs of the multiblock copolymers were also compared to the T_gs of the polymer blends of the corresponding homopolymers, and we found that T_gs of the polymer blends were similar to those of the respective homopolymers, as expected. SAXS experiments further demonstrated microphase separation of multiblock copolymers. This work demonstrates the enormous potential of multiblock architectures to tune the physical properties of synthetic polymers, by changing their glass transition temperature and their morphologies obtained from microphase separation, with domain sizes reaching under 10 nm.

中文翻译：

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序列控制的多嵌段共聚物链段的变化导致微相分离的演变

多嵌段共聚物（MBCP）是新兴的一类材料，近年来变得越来越容易获得。然而，迄今为止，仍缺乏对其物理性质的基本了解。特别是，已知受相分离影响的玻璃化转变温度（T _g）在实验上还没有很好地表征。为此，我们报告了关于T _g s的演变以及相应的线性MBCP随相变数目增加而保持整体聚合度（DP）恒定（DP = 200）的相分离的第一项实验研究。乙二醇甲基醚丙烯酸酯（EGMEA）和叔选择丙烯酸丁酯（tBA）作为可逆加成-断裂链转移聚合反应合成MBCP的单体。我们发现MCBP中EGMEA和tBA片段的T _g s（通过差示扫描量热法测量）随着块数量的增加和块长度的减小而收敛，这与从小角度X射线观察到的异质性损失有关散射（SAXS）分析。该Ť_克多嵌段共聚物第也相比于Ť_克相应的均聚物的聚合物共混物的s和我们发现Ť_克如所预期的，聚合物共混物的s与各个均聚物的s相似。SAXS实验进一步证明了多嵌段共聚物的微相分离。这项工作证明了通过改变合成聚合物的玻璃化转变温度和通过微相分离获得的形态来调整合成聚合物的物理性质的巨大潜力，其畴尺寸达到10 nm以下。