Structure of Poly(styrene-b-ethylene-alt-propylene) Diblock Copolymer Micelles in Squalane
Structure of Poly(styrene-b-ethylene-alt-propylene) Diblock Copolymer Micelles in Squalane
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DOI：
10.1021/jp8111149
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发表时间：
2009-10-22
影响因子：
3.3
通讯作者：
Lodge, Timothy P.
中科院分区：
文献类型：
--
作者：
Choi, Soo-Hyung;Bates, Frank S.;Lodge, Timothy P.
用动态光散射（DLS）和小角X射线散射（SAXS）研究了聚（苯乙烯-b-乙烯-alt-丙烯）（SEP）二嵌段共聚物在角鲨烷（PEP嵌段的高度选择性溶剂）中形成胶束结构的温度依赖性。通过苯乙烯和异戊二烯的连续阴离子聚合，然后异戊二烯嵌段的氢化，制备四种SEP二嵌段共聚物，得到SEP（17-73）、SEP（26-66）、SEP（36-69）和SEP（42-60），其中数字表示以kDa计的嵌段分子量。所有聚合物形成了明确的球形胶束。在稀溶液中，DLS提供了与温度相关的平均流体动力学半径R-h及其分布，而SAXS曲线的详细拟合给出了核心半径R-c、等效硬球半径R-hs和聚集数N-agg的估计值。在一般情况下，胶束变得更小的临界胶束温度（CMT）的方法，这是远远高于核心块的玻璃化转变。随着浓度的增加，胶束填充到所有四种共聚物的体心立方晶格上，在稀溶液CMT附近加热时经历有序-无序转变。讨论了嵌段共聚物溶液自组装的结果，特别注意的是支付10平衡的问题，考虑到高的玻璃化转变温度的核心块。
The temperature dependence of the micellar structures formed by poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymers in squalane, it highly selective solvent for the PEP blocks, has been Studied using, dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). Four SEP diblock copolymers were prepared by sequential anionic polymerization of styrene and isoprene, followed by hydrogenation of the isoprene blocks, to yield SEP(17-73), SEP(26-66), SEP(36-69), and SEP(42-60), where the numbers indicate block molecular weights in kDa. All lour polymers formed well-defined spherical micelles. In dilute solution, DLS provided the temperature-dependent mean hydrodynamic radius, R-h, and its distribution, while detailed fitting of the SAXS profiles gave the core radius, R-c, the equivalent hard sphere radius, R-hs, and an estimate of the aggregation number, N-agg. In general, the micelles became smaller as the critical micelle temperature (CMT) was approached, which was well above the glass transition of the core block. As concentration increased the micelles packed onto body centered cubic lattices for all Four copolymers, which underwent order-disorder transitions upon heating near the dilute solution CMTs. The results are discussed in terms Of Current understanding of block copolymer solution self-assembly, and particular attention is paid 10 the issue of equilibration, given the high glass transition temperature of the core block.