Paciolla Mariarita, Likos Christos N, Moreno Angel J
Centro de Física de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain.
Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria.
Macromolecules. 2022 Apr 12;55(7):2659-2674. doi: 10.1021/acs.macromol.1c02610. Epub 2022 Mar 24.
We perform simulations to compute the effective potential between the centers-of-mass of two polymers with reversible bonds. We investigate the influence of the topology on the potential by employing linear and ring backbones for the precursor (unbonded) polymer, finding that it leads to qualitatively different effective potentials. In the linear and ring cases the potentials can be described by Gaussians and generalized exponentials, respectively. The interactions are more repulsive for the ring topology, in analogy with known results in the absence of bonding. We also investigate the effect of the specific sequence of the reactive groups along the backbone (periodic or with different degrees of randomness), establishing that it has a significant impact on the effective potentials. When the reactive sites of both polymers are chemically orthogonal so that only intramolecular bonds are possible, the interactions become more repulsive the closer to periodic the sequence is. The opposite effect is found if both polymers have the same types of reactive sites and intermolecular bonds can be formed. We test the validity of the effective potentials in solution, in a broad range of concentrations from high dilution to far above the overlap concentration. For this purpose, we compare simulations of the effective fluid and test particle route calculations with simulations of the real all-monomer system. Very good agreement is found for the reversible linear polymers, indicating that unlike in their nonbonding counterparts many-body effects are minor even far above the overlap concentration. The agreement for the reversible rings is less satisfactory, and at high concentration the real system does not show the clustering behavior predicted by the effective potential. Results similar to the former ones are found for the partial self-correlations in ring/linear mixtures. Finally, we investigate the possibility of creating, at high concentrations, a gel of two interpenetrated reversible networks. For this purpose we simulate a 50/50 two-component mixture of reversible polymers with orthogonal chemistry for the reactive sites, so that intermolecular bonds are only formed between polymers of the same component. As predicted by both the theoretical phase diagram and the simulations of the effective fluid, the two networks in the all-monomer mixture do not interpenetrate, and phase separation (demixing) is observed instead.
我们进行模拟，以计算具有可逆键的两种聚合物质心之间的有效势。我们通过使用前驱体（未键合）聚合物的线性和环状主链来研究拓扑结构对势的影响，发现这会导致定性不同的有效势。在直线型和环状情况下，势分别可以用高斯函数和广义指数函数来描述。与无键合情况下的已知结果类似，环状拓扑结构的相互作用更具排斥性。我们还研究了沿着主链的反应基团的特定序列（周期性或具有不同程度的随机性）的影响，确定其对有效势有显著影响。当两种聚合物的反应位点在化学上是正交的，以至于只可能形成分子内键时，序列越接近周期性，相互作用就越具排斥性。如果两种聚合物具有相同类型的反应位点并且可以形成分子间键，则会发现相反的效果。我们在从高稀释到远高于重叠浓度的广泛浓度范围内，测试了溶液中有效势的有效性。为此，我们将有效流体和测试粒子路径计算的模拟与真实全单体系统的模拟进行了比较。对于可逆线性聚合物，发现了非常好的一致性，这表明与它们的非键合对应物不同，即使在远高于重叠浓度时，多体效应也很小。对于可逆环状聚合物，一致性不太令人满意，并且在高浓度下，真实系统并未表现出有效势所预测的聚集行为。对于环状/线性混合物中的部分自相关，发现了与前者类似的结果。最后，我们研究了在高浓度下创建由两个相互贯穿的可逆网络组成的凝胶的可能性。为此，我们模拟了一种 50/50 的两组分可逆聚合物混合物，其反应位点具有正交化学性质，使得分子间键仅在相同组分的聚合物之间形成。正如理论相图和有效流体模拟所预测的那样，全单体混合物中的两个网络不会相互贯穿，而是观察到相分离（分层）现象。
