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Coil to globule transition of homo- and block-copolymer with different topological constraint and chain stiffness

Science China Chemistry 2015年第9期58卷 1471-1477页

作者： Wei Wang Yanchun Li Zhongyuan Lu State Key Laboratory of Supramolecular Structure and Materials Institute of Theoretical Chemistry Jilin University

In this paper, we present the coil-to-globule(CG) transitions of homopolymers and multiblock copolymers with different topology and stiffness by using molecular dynamics with integrated tempering sampling method. The sampling method was a novel enhanced method that efficiently sampled the energy space with low computational costs. The method proved to be efficient and precise to study the structural transitions of polymer chains with complex topological constraint, which may not be easily done by using conventional Monte Carlo method. The topological constraint affects the globule shape of the polymer chain, thus further influencing the CG transition. We found that increasing the topological constraint generally decreased CG transition temperature for homopolymers. For semiflexible chains, an additional first-order like symmetry-broken transition emerged. For block copolymers, the topological constraint did not obviously change the transition temperature, but greatly reduced the energy signal of the CG transition.

关键词： coil-to-globule transition topological constraint chain stiffness molecular dynamics

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Size and Dynamics of Ring Polymers under Different topological constraints

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Chinese Journal of Polymer Science 2023年第4期41卷 516-524,I0006页

作者： Jiang-Yang Mo Zhen-Hua Wang Yu-Yuan Lu Li-Jia An State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun130022China University of Science and Technology of China Hefei230026China

The impact of ring polymer length N and the influence of interchain and intrachain interactions on the size and dynamic behaviors of ring polymers,including the structural relaxation time τ_(R) and self-diffusion coefficient D,remain poorly understood at present due to a lack of systematic studies with relatively large N *** work addressed this issue by applying dynamic Monte Carlo simulations with independently tuned interchain and intrachain interactions to investigate the size and dynamics of the ring melts with chain lengths over a wide range of 0.2N_(e)≤N≤80N_(e)(N_(e) is the entanglement length of corresponding linear chains)under different topological constraints,including all-crossing and intercrossing *** found that it was inappropriate to treat the unknotting constraint free energy of the ring chains in the melts as the free energy contributed by the excluded volume interactions of polymers in a good *** exponents of 2.5 and 1.5 reflecting the Ndependence of τ_(R) were obtained for long ring chains in non-crossing and intra-crossing systems,respectively,suggesting that the ring chains behaved as individual clusters and exhibited Zimm-like dynamics in intra-crossing systems.A single scaling exponent of-2 reflecting the Ndependence of D was obtained for ring chains in non-crossing and intra-crossing systems,indicating that the intrachain constraints affected only the value of D,and had little influence on the scaling relationship between D and ***,the extended Stokes-Einstein relation broke down for the ring chains in the non-crossing and intra-crossing systems because the structural relaxation and translational diffusion were decoupled for the short ring systems,while both the translational diffusion and rotational relaxations,as well as diffusion at short and long time scales,were decoupled for long ring systems.

关键词： Ring polymer topological constraint Extended Stokes-Einstein relation Monte Carlo simulation

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