The dilute solution properties of poly(d,l-lactide)s (PDL50) with a weight-averaged molar mass (Mw) ranging from 0.154 × 104 to 75.7 × 104 g mol−1 are thoroughly studied in tetrahydrofuran at 25 °C by static light and small-angle X-ray scattering and intrinsic viscosity ([η]) measurements. Fourteen PDL50 samples with a narrow molar mass distribution are synthesized at 150 °C by ring-opening copolymerization of a 1:1 mixture of d-lactide and l-lactide with benzyl alcohol as an initiator and tin(II) dichloride dihydrate as the catalyst, followed by fractionation using recycling preparative size exclusion chromatography. The Mw dependences of the z-averaged root-mean-square radius of gyration (〈S2〉z1/2) and [η] are rationalized and analyzed based on the cylindrical wormlike chain model. The experimental Mw dependence of 〈S2〉z1/2 is quantitatively described by the wormlike cylinder with stiffness parameter λ−1 = 2.9 nm, molar mass per unit contour length ML = 270 ± 20 g mol−1 nm−1, protruding effects at both ends δ = 0.4 nm, and excluded-volume strength B = 0.31 ± 0.07 nm. The experimental Mw dependence of [η] and the scattering form factor P(q) are also consistently expressed by the current theories with the same model parameters. The results indicate that the PDL50 chain behaves as a typical flexible polymer but is essentially 1.6−2.1 times stiffer than the representative vinyl polymers, polystyrene (λ−1 = 1.8 nm) and poly(methyl methacrylate) (λ−1 = 1.4 nm), most likely due to the planar feature of the ester linkage, which partially constrains the free rotation of the main chain. The dilute solution properties of poly(d,l-lactide)s (PDL50) with a weight-averaged molar mass (Mw) ranging from 0.154 × 104 to 75.7 × 104 g mol−1 are thoroughly studied in tetrahydrofuran at 25 °C by static light and small-angle X-ray scattering and intrinsic viscosity ([η]) measurements. The Mw dependences of 〈S2〉z1/2 and [η] are quantitatively described by the wormlike cylinder with stiffness parameter λ−1 = 2.9 nm, indicating that the PDL50 chain behaves as a typical flexible polymer but is essentially 1.6−2.1 times stiffer than polystyrene and poly(methyl methacrylate).

中文翻译：

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通过静态光散射、SAXS 和特性粘度稀释聚 (d,l-丙交酯) 的溶液特性

重均摩尔质量 (Mw) 范围为 0.154 × 104 至 75.7 × 104 g mol-1 的聚 (d,l-丙交酯) (PDL50) 的稀溶液性质在 25 °C 的四氢呋喃中进行了彻底研究。静态光和小角度 X 射线散射和特性粘度 ([η]) 测量。通过将 d-丙交酯和 l-丙交酯的 1:1 混合物与作为引发剂的苯甲醇和二水合二氯化锡 (II) 的 1:1 混合物开环共聚，在 150 °C 下合成了 14 个具有窄摩尔质量分布的 PDL50 样品，然后使用回收制备型尺寸排阻色谱进行分馏。基于圆柱状蠕虫链模型，对 z 平均均方根回转半径 (<S2>z1/2) 和 [η] 的 Mw 依赖性进行了合理化和分析。〈S2〉z1/2 的实验 Mw 依赖性由具有刚度参数 λ−1 = 2.9 nm、每单位轮廓长度的摩尔质量 ML = 270 ± 20 g mol−1 nm−1、突出效应的蠕虫状圆柱体定量描述两端 δ = 0.4 nm，排除体积强度 B = 0.31 ± 0.07 nm。[η] 的实验 Mw 依赖性和散射形状因子 P(q) 也由具有相同模型参数的当前理论一致表达。结果表明，PDL50 链表现为典型的柔性聚合物，但基本上比代表性乙烯基聚合物、聚苯乙烯（λ-1 = 1.8 nm）和聚（甲基丙烯酸甲酯）（λ-1 = 1.4 nm）硬 1.6-2.1 倍，很可能是由于酯键的平面特征，这部分限制了主链的自由旋转。poly(d, 重均摩尔质量 (Mw) 范围为 0.154 × 104 至 75.7 × 104 g mol-1 的 l-丙交酯 (PDL50) 在 25 °C 的四氢呋喃中通过静态光和小角度 X 射线进行彻底研究散射和特性粘度 ([η]) 测量。〈S2〉z1/2 和 [η] 的 Mw 依赖性由刚度参数 λ−1 = 2.9 nm 的蠕虫状圆柱体定量描述，表明 PDL50 链表现为典型的柔性聚合物，但本质上是刚性的 1.6−2.1 倍比聚苯乙烯和聚（甲基丙烯酸甲酯）。