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Morphological studies of homopolymer/block copolymer blends with exothermic interfacial mixing

机译：放热界面混合下均聚物/嵌段共聚物共混物的形态研究

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摘要

It is well-established that block copolymers A-b-B, whose segments are incompatible, can function as emulsifiers in blends of homopolymers of A and B. In such blends, the volume fractions of the blend constituents determine the morphology; and the emulsifying power is primarily dictated by the molecular weight ratio of homopolymer to block copolymer. However, when there is exothermic mixing between one of the block copolymer segments and one homopolymer, the role of the molecular weight ratios becomes less significant, since the competition between exothermic and endothermic interactions can strongly influence the morphology.;We have explored the influence of molecular weight ratio, degree of exothermic mixing, incompatibility across an interface, and balance of interfacial swelling on the morphology of solvent-cast films using transmission electron microscopy. Microphase formation in binary A/X-b-B blends is facilitated, when entropic mixing between homopolymer A and block X is insufficient, by exothermic mixing between A and X. Uniform microphase separation can occur with a low molecular weight block copolymer when the homopolymer A has M scA $>$ M scX, and when there is a polydisperse distribution in M scA. However, microphase formation is observed within a window: the upper limit is defined by too high molecular weight of the homopolymer and/or of the block copolymer, coupled with a large repulsion $chi$ scAB, which leads to macrophase segregation; the lower bound is determined by a too small repulsion $chi$ scAB, and/or a too negative $chi$ scAX which results in formation of homogeneous phase.;In ternary A/A-b-B/B or A/X-b-B/B blends, the tendency of the block copolymer to migrate to the interface (interfacial activity) depends on incompatibility of homopolymer A with block B and between homopolymer B and block A or X (N$chi$ scAB and N$chi$ scBA or N$chi$ scBX, respectively). When the block copolymer is interfacially active, modulation of the balance of interfacial swelling of the block copolymer segments can be used to generate a rich variety of morphologies. In addition, when the swelling of a block copolymer segment by the minor phase is sufficiently large relative to that in the major phase, the minor phase becomes the continuous matrix, forming a polygonal network morphology. Conversely, strong interfacial swelling of the coronae by the major phase lowers the emulsifying power of a block copolymer as evidenced by the co-existence of microphase with macrophase even in the presence of a relatively large quantity of block copolymer.
机译：众所周知，链段不相容的嵌段共聚物A-b-B在A和B均聚物的共混物中可以起乳化剂的作用。在这种共混物中，共混物成分的体积分数决定了形态。乳化能力主要由均聚物与嵌段共聚物的分子量比决定。但是，当嵌段共聚物链段之一与一种均聚物之间放热混合时，分子量比的作用变得不那么重要了，因为放热和吸热相互作用之间的竞争会强烈影响形貌。分子量比，放热混合度，界面不相容性以及使用透射电子显微镜观察的溶剂流延膜形态上的界面溶胀平衡。当均聚物A和嵌段X之间的熵混合不充分时，通过A和X之间的放热混合，可促进二元A / XbB共混物中的微相形成。当均聚物A具有M scA时，低分子量嵌段共聚物会发生均匀的微相分离$> $ M scX，并且在M scA中存在多分散分布。但是，在窗口内观察到微相的形成：上限由均聚物和/或嵌段共聚物的分子量过高，再加上大的斥力scAB引起，从而导致宏观相分离。下限由排斥力$ chi $ scAB和/或负离子$ chi $ scAX决定，导致形成均相；在三元A / AbB / B或A / XbB / B共混物中，嵌段共聚物迁移到界面的趋势（界面活性）取决于均聚物A与嵌段B以及均聚物B与嵌段A或X之间的不相容性（N $ chi $ scAB和N $ chi $ scBA或N $ chi $ scBX ， 分别）。当嵌段共聚物是界面活性的时，可以使用调节嵌段共聚物链段的界面溶胀平衡的方式来产生多种形态。另外，当嵌段共聚物链段被次要相的溶胀相对于主要相中的溶胀足够大时，次要相变为连续基质，形成多边形网络形态。相反，主相的强电晕界面溶胀降低了嵌段共聚物的乳化能力，这通过微相与大相的共存来证明，即使存在相对大量的嵌段共聚物也是如此。

著录项

  • 作者

    Adedeji, Adeyinka.;

  • 作者单位

    Case Western Reserve University.;

  • 授予单位 Case Western Reserve University.;
  • 学科 Plastics.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 199 p.
  • 总页数 199
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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