Crystallization-Induced Self-Assembly of Poly(ethylene glycol) Side Chains in Dithiol-yne-Based Comb Polymers: Side Chain Spacing and Molecular Weight Effects.

Abstract

The chain architecture and topology of macromolecules impact their physical properties and final performance, including their crystallization process. In this work, comb polymers constituted by poly(ethylene glycol), PEG, side chains, and a dithiol-yne-based ring polymer backbone have been studied, focusing on the micro- and nanostructures of the system, thermal behavior, and crystallization kinetics. The designed comb system allows us to investigate the role of a ring backbone, the impact of varying the distance between two neighboring side chains, and the effect of the molecular weight of the side chain. The results reflect that the governing factor in the crystalline properties is the molar mass of the side chains and that the tethering of PEG chains to the ring backbone brings important constraints to the crystallization process, reducing the crystallinity degree and slowing down the crystallization kinetics in comparison to analogue PEG homopolymers. We demonstrate that the effect of spatial hindrance in the comb-like PEG polymers drives the morphology toward highly ordered, self-assembled, semicrystalline superstructures with either extended interdigitated chain crystals or novel (for comb polymers) interdigitated folded chain lamellar crystals. These structures depend on PEG molecular weight, the distance between neighboring tethered PEG chains, and the crystallization conditions (nonisothermal versus isothermal). This work sheds light on the role of chain architecture and topology in the structure of comb-like semicrystalline polymers.