Probing phase-separation behavior in polymer-blend microparticles: Effects of particle size and polymer mobility
Probing phase-separation behavior in polymer-blend microparticles: Effects of particle size and polymer mobility
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DOI：
10.1021/ma990846r
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发表时间：
1999-10-19
期刊：
影响因子：
5.5
通讯作者：
Noid, DW
中科院分区：
文献类型：
--
作者：
Barnes, MD;Ng, KC;Noid, DW
我们描述了一种新的方法来探测聚合物共混体系在球形微粒中的相分离，这些微粒是由稀溶液中的微滴产生的。二维光学衍射是一种在大约30纳米的长度尺度上对材料不均匀性敏感的技术，用于探测阿托升和飞升体积的大体积不相容聚合物的相分离行为。在溶剂快速挥发(约2-10ms)和相对较低的聚合物迁移率的条件下，可以使用在本体制剂中通常经历相分离的不同聚合物来形成均匀的复合颗粒。我们发现，对于均匀的粒子，折射率(与材料的介电常数有关)可以通过调节聚合物在混合物中的相对重量分数来调节。对聚合物共混纳米粒子进行了分子动力学模拟，在分子水平上阐明了聚合物相互作用和边界条件对聚合物共混纳米粒子相分离的影响。最后，我们发现聚合物的流动性会影响低分子量(高迁移率)聚乙二醇齐聚体与聚乙烯醇S混合物在微粒中的相分离行为。对于较高相对分子质量的聚合物(>；10K)，表面能限制阻碍了相分离，并且观察到聚合物共混粒子在实验分辨率范围内是均匀的。相反，低分子量聚乙二醇乙二醇酯与聚乙烯醇的共混物在几分钟的时间尺度上相分离，形成不均匀的复合颗粒。
We describe a new method for probing phase separation of polymer-blend systems in spherical microparticles generated from microdroplets of dilute polymer solution. Two-dimensional optical diffraction-a technique sensitive to material inhomogeneity on a length scale of approximate to 30 nm-is used to probe phase-separation behavior of bulk-immiscible polymers in attoliter and femtoliter volumes. Under conditions of rapid solvent evaporation (approximate to 2-10 ms) and relatively low polymer mobility, homogeneous composite particles can be formed using different polymers that ordinarily undergo phase separation in bulk preparations. We show that, for homogeneous particles, the refractive index (related to material dielectric constant) can be tuned by adjusting the relative weight, fractions of polymers in the blend. Molecular dynamics simulations of polymer-blend microparticles are presented to illustrate at a molecular level effects of polymer interactions and boundary conditions on phase separation in polymer-blend nanoparticles. Finally, we show that polymer mobility affects phase-separation behavior in microparticles using mixtures of poly(vinyl alcohol)s with low molecular weight (high-mobility) poly(ethylene glycol) oligomers. For higher molecular weight polymers (>10 K), surface energy constraints inhibit phase separation, and the polymer-blend particles are observed to be homogeneous to within experimental resolution. Conversely, blends of low molecular weight PEG with PVA phase-separate on a time scale of several minutes to form heterogeneous composite particles.