Single molecule mechanics of poly(styrene) polymer chains is investigated in different organic solvents with atomic force microscopy (AFM). The acquired force–extension profiles can be well fitted with a modified freely jointed chain (FJC) model. The model describes the force–extension profiles in terms of an apparent Kuhn length and an elasticity constant. The elasticity constant is found to be the same for all different solvents investigated. Best fit of the force–extension profiles with the FJC model reveals that the Kuhn length varies systematically with solvent quality. In fact, one can establish a good correlation between the Kuhn length and the Flory–Huggins interaction parameter. The increase in the Kuhn length with increasing solvent quality reflects the larger extent of swelling of the polymer in good solvents.

中文翻译：

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溶剂质量对单个聚（苯乙烯）聚合物链的力响应的影响

用原子力显微镜 (AFM) 在不同的有机溶剂中研究了聚 (苯乙烯) 聚合物链的单分子力学。获得的力-延伸曲线可以很好地拟合修改后的自由连接链 (FJC) 模型。该模型根据表观库恩长度和弹性常数来描述力-延伸曲线。对于所研究的所有不同溶剂，发现弹性常数是相同的。与 FJC 模型的力-延伸曲线的最佳拟合表明，库恩长度随溶剂质量系统地变化。事实上，可以在库恩长度和弗洛里-哈金斯相互作用参数之间建立良好的相关性。随着溶剂质量的提高，库恩长度的增加反映了聚合物在良溶剂中的更大程度的溶胀。