Comparison of chain-growth polymerization in solution versus on surface using reactive coarse-grained simulations. (27th October 2017)

• Record Type: Journal Article
• Authors: Deng, Binghui; Palermo, Edmund F.; Shi, Yunfeng
• Is Part Of: Polymer. Volume 129(2017)
• Page Start: 105
• Page End: 116
• Publication Date: 2017-10-27
• Subjects: Reactive force field -- Surface-initiated polymerization -- Chain distribution -- Dispersity -- Polymer brush; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2017.09.048
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: We developed a reactive coarse-grained model for chain-growth polymerization to study the chain length distribution of polymers grafted from a surface as compared to those grown in solution. The surface-initiated polymer chains exhibit a markedly broader distribution of chain lengths (larger dispersity) and slower chain growth kinetics as compared to the solution phase process. Two key factors that cause deviation from ideal grafting are identified: (1) the formation of chain "loops" with both termini attached to the substrate via recombination and (2) the "starvation" effect, in which the live chain ends of short polymers are sterically shielded from monomers by the presence of longer neighboring chains. Both effects are markedly amplified with increasing initiator surface density, thus limiting the density of high molecular weight chains grafted from the surface. Whereas the "loop" effect is absent in systems that are very strictly "living" (no termination), the starvation effect is likely operative in most real systems. Taken together, these results suggest a theoretical limit on the density of polymer brushes that can form on surfaces by a "grafting-from" technique, based on the kinetics of the chain-growth polymerization process. Graphical abstract: Highlights: A reactive coarse-grained model capable of chain-growth polymerization is developed. Surface-initiated polymer brush has higher dispersity than those grown in solutions. Both looped chain and starved chains cause deviation from ideal grafting on substrate. The results suggest a theoretical limit on the grafting density of polymer brush.