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Order and Disorder in High χ/Low N, Broad Dispersity ABA Triblock Polymers
Macromolecules ( IF 5.1 ) Pub Date : 2017-08-31 00:00:00 , DOI: 10.1021/acs.macromol.7b01452 Adam K. Schmitt 1 , Mahesh K. Mahanthappa 1, 2
Macromolecules ( IF 5.1 ) Pub Date : 2017-08-31 00:00:00 , DOI: 10.1021/acs.macromol.7b01452 Adam K. Schmitt 1 , Mahesh K. Mahanthappa 1, 2
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Using a combination of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), we document the composition-dependent morphologies of 39 new poly(lactide-block-1,4-butadiene-block-lactide) (LBL) block polymers, comprising a broad dispersity B segment (Mn = 4.5–17.7 kg/mol; Đ = Mw/Mn = 1.72–1.88) and narrow dispersity L end blocks (Mn = 0.6–15.3 kg/mol; Đ = 1.10–1.21) with volume fractions 0.26 ≤ fB ≤ 0.95. A subset of these samples undergo melt self-assembly into cylindrical, lamellar, and apparently bicontinuous morphologies. By assessing the states of order and disorder in these triblock polymer melts using temperature-dependent SAXS, we find that broad B segment dispersity increases the minimum segregation strength χN ≳ 27 required for LBL triblock self-assembly relative to the self-consistent mean-field theory prediction χN ≥ 17.9 for narrow dispersity analogues. While B segment dispersity has previously been shown to thermodynamically stabilize the self-assembled morphologies of low χ/high N ABA triblocks, the present study indicates that broad B block dispersity in related high χ/low N systems destabilizes the microphase-separated melt. These observations are rationalized in terms of recent theories that suggest that broad segmental dispersity substantially enhances fluctuation effects at low N, thus disfavoring melt segregation.
中文翻译：
高χ/低N宽分散ABA三嵌段聚合物的有序和无序。
使用小角度X射线散射（SAXS）和透射电子显微镜（TEM）的组合，我们记录了39种新的聚丙交酯-嵌段-1,4-丁二烯-嵌段-丙交酯（LBL）的成分依赖性形态）嵌段聚合物，包括宽分散性B链段（M n = 4.5-17.7 kg / mol；Đ = M w / M n = 1.72-1.88）和窄分散性L端嵌段（M n = 0.6-15.3 kg / mol；Đ = 1.10-1.21）与体积分数0.26≤ ˚F乙≤0.95。这些样品中的一部分会经历熔体自组装成圆柱形，层状和显然双连续的形态。通过评估的有序和无序在使用依赖于温度的SAXS这些三嵌段聚合物熔体的状态，我们发现，宽乙段分散度增加最小分离强度χ Ñ ≳27所需LBL三嵌段自组装相对于自洽均值场理论预测χ ñ ≥17.9窄分散度类似物。虽然先前已证明B段的分散性在热力学上稳定了低χ/高N ABA三嵌段的自组装形态，但本研究表明，在相关的高χ/低N中，宽广的B嵌段分散性系统破坏了微相分离的熔体的稳定性。这些观点根据最新的理论进行了合理化，这些理论表明，宽的链段分散性在低氮下显着增强了波动效应，从而不利于熔体偏析。
更新日期：2017-08-31
中文翻译：
高χ/低N宽分散ABA三嵌段聚合物的有序和无序。
使用小角度X射线散射（SAXS）和透射电子显微镜（TEM）的组合，我们记录了39种新的聚丙交酯-嵌段-1,4-丁二烯-嵌段-丙交酯（LBL）的成分依赖性形态）嵌段聚合物，包括宽分散性B链段（M n = 4.5-17.7 kg / mol；Đ = M w / M n = 1.72-1.88）和窄分散性L端嵌段（M n = 0.6-15.3 kg / mol；Đ = 1.10-1.21）与体积分数0.26≤ ˚F乙≤0.95。这些样品中的一部分会经历熔体自组装成圆柱形，层状和显然双连续的形态。通过评估的有序和无序在使用依赖于温度的SAXS这些三嵌段聚合物熔体的状态，我们发现，宽乙段分散度增加最小分离强度χ Ñ ≳27所需LBL三嵌段自组装相对于自洽均值场理论预测χ ñ ≥17.9窄分散度类似物。虽然先前已证明B段的分散性在热力学上稳定了低χ/高N ABA三嵌段的自组装形态，但本研究表明，在相关的高χ/低N中，宽广的B嵌段分散性系统破坏了微相分离的熔体的稳定性。这些观点根据最新的理论进行了合理化，这些理论表明，宽的链段分散性在低氮下显着增强了波动效应，从而不利于熔体偏析。
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