Effect of branching and molecular weight on the viscoelastic properties of poly(butyl acrylate)
Effect of branching and molecular weight on the viscoelastic properties of poly(butyl acrylate)
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DOI：
10.1002/pola.10424
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发表时间：
2002-10-15
影响因子：
--
通讯作者：
Gilbert, RG
中科院分区：
文献类型：
--
作者：
Former, C;Castro, J;Gilbert, RG
通过乳液聚合制备了一系列具有一定分子量和链支化度的聚（丙烯酸丁酯）样品。通过 NMR（给出支化分数，范围约为 0 至 7%）、凝胶渗透色谱、粘度测定法和凝胶分数测定进行表征。动态机械响应，即储能模量和损耗模量 G'(omega) 和 G"(omega) 的频率依赖性，在 0.02 至 200 Hz 范围内进行测量。样品中出现显着的不溶部分意味着不可能全面表征分子量分布，因此无法明确区分机械响应对长链支化 (LCB) 和短链支化 (SCB) 程度以及分子量的依赖性；然而，仅依赖于分子量的趋势不足以对结果进行建模，在高频下，G'(omega) 和 G"(omega) 的所有趋势都可以归因于分子量依赖性；在低频下，可以推断出分子量和总支化度的影响，支化度越高的样品表现出较低的储能模量和损耗模量。虽然无法确定 SCB 和 LCB 的相对量，但没有观察到 LCB 的动态特征。如果假设 SCB 程度的增加导致管尺寸增加，则低频趋势可以半定量地与蠕动和回缩理论拟合。 (C) 2002 年 Wiley 期刊公司
A series of poly(butyl acrylate) samples were prepared by emulsion polymerization with a range of molecular weights and degrees of chain branching. Characterization was performed with NMR (giving the fraction of branching, ranging from approximately 0 to 7%), gel permeation chromatography, viscometry, and determination of the gel fraction. The dynamic mechanical response, that is, the frequency dependence of the storage and loss moduli G'(omega) and G"(omega) was measured from 0.02 to 200 Hz. The occurrence of a significant insoluble fraction in the sample meant that full characterization of the molecular weight distribution was not possible, and so an unambiguous separation of the dependencies of the mechanical response on the degree of long-chain branching (LCB) and short-chain branching (SCB) and the molecular weight could not be made; however, trends dependent on the molecular weight alone were insufficient to model the results. At high frequencies, all trends in G'(omega) and G"(omega) could be ascribed to molecular weight dependencies; at low frequencies, the effects of both the molecular weight and total degree of branching could be inferred, with more highly branched samples showing lower storage and loss moduli. Although the relative amounts of SCB and LCB could not be determined, no dynamic features attributable to LCB were observed. The low-frequency trends could be semiquantitatively fitted with reptation and retraction theory if it was assumed that an increased degree of SCB led to an increased tube size. (C) 2002 Wiley Periodicals, Inc.