Internal dynamics of polymer chains is one of the most important fundamental problems in polymer physics. This work reports the first example of a dynamic light scattering (DLS) study of internal motions of well-defined ultralong comb-like chains in dilute solutions under good solvent conditions. Using two well-characterized comb-like model samples with controlled parameters and narrow distributions (M_w/M_n ≈ 1.30 and M_w ≈ 10⁷ g/mol), the asymptotic behavior of the reduced first cumulant [Γ* = Γ(q)/(q³k_BT/η₀)], the number of relaxation modes in Γ(q) distribution curves, the characteristic relaxation time (τ₁) of the first internal mode, and the q-dependent relative strength of internal motions have been experimentally quantified and carefully analyzed where q is the scattering vector. Specifically, the DLS results reveal the following: (i) Γ*(q ≫ 1), that is, the value of Γ* at the very high q regime, is not sensitive to structural details (local rigidity and side chain length); (ii) similar to hyperbranched polymers, the asymptotic power law in the regime of 3.0 < (q⟨R_g⟩) < 5.5 is also found to be a better indicator, which could reflect the structural details for comb-like polymers; (iii) the comparison of experimentally determined and theoretically calculated values of τ₁ shows that the classical theory of linear chains could still satisfactorily describe the intrachain relaxation behavior of comb-like chains; and (iv) the side-chain grafting-induced rigidity could result in an enhanced separation of translational and internal motions but simultaneously result in a significant suppression of the strength of overall internal motions. The present study not only reveals that the modes of internal motions of a given system are mainly determined by the relaxation of the main contour of a given chain structure rather than the local chain rigidity but also provides useful experimental data for further theoretical modeling of internal dynamics of various topological polymers.

中文翻译：

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良好溶剂条件下超长梳状链在稀溶液中内部运动的光散射研究

聚合物链的内部动力学是聚合物物理学中最重要的基本问题之一。这项工作报告了动态光散射（DLS）研究的第一个示例，该研究研究了良好溶剂条件下稀溶液中定义明确的超长梳状链的内部运动。使用两个良好表征的梳状具有受控参数和窄分布模型样品（中号_瓦特/中号_Ñ ≈1.30和中号_瓦特≈10 ⁷克/摩尔），减小的第一累积量的渐近行为[Γ* =Γ（q）/（q ³ ķ_乙Ť /η ₀）]，（在Γ放松模式的数量q）分布曲线，特征弛豫时间（τ ₁第一内部模式的），并且q内部运动的依赖性相对强度进行了实验定量，并仔细地分析，其中q是散射向量。具体而言，DLS结果揭示了以下内容：（i）Γ*（q≫ 1），即在非常高的q态下的Γ*值对结构细节（局部刚度和侧链长度）不敏感；（ⅱ）类似于超支化聚合物，在3.0 <政权渐近幂律（q ⟨ ř_克5.5）<5.5也被认为是更好的指标，它可以反映梳状聚合物的结构细节；（ⅲ）τ的实验确定的和理论计算值的比较₁表明经典的线性链理论仍然可以令人满意地描述梳状链的链内弛豫行为。（iv）侧链接枝诱导的刚性可能导致平移运动和内部运动的分离增强，但同时导致整体内部运动强度的显着抑制。本研究不仅揭示给定系统的内部运动模式主要由给定链结构的主轮廓的松弛而不是局部链的刚度决定，而且还为进一步的内部动力学理论建模提供了有用的实验数据。各种拓扑聚合物。