Study of Linear and Cyclic Graft Polystyrenes with Identical Backbone Contour in Dilute Solutions: Preparation, Characterization, and Conformational Properties

Exploring the difference in the topology-structure-conformation relationship for linear and cyclic graft polymers is an interesting topic. In this work, two libraries of linear graft (l-PPA-g-PS, with a linear backbone) and cyclic graft (c-PPA-g-PS, with a cyclic backbone) polystyrenes with low ratios of the backbone-to-sidechain contour length (r(c), from 1.26 to 6.22) and various grafting densities (sigma, from 0.16 to 0.86) have been studied as models. Atomic force microscopy (AFM) characterization has indicated ellipsoidal and spherical morphologies for both l-PPA-g-PS and c-PPA-g-PS with no significant difference. By comparing the absolute (M-w,M-abs) and apparent (M-w,M-app) molar masses, it is found that M-w,M-abs/M-w,M- app varies from 1.5 to 3.5 and gradually increases with sigma. By measuring g(h)(1/2) (g(h)(1/2) = R-h,R-graft/R-h,R-linear), it is found that the two topologies have different compactness of conformation. By following the temperaturedependent interchain aggregation in cyclohexane, it is found that the cyclic backbone feature can suppress the interchain association and be more susceptible to graft density than linear graft polymers. The present study has clearly showed that the cyclic graft topology can potentially display unique structural and conformational properties, which can be attributed to the topological advantages such as more compact conformation and significant isotropic features.

Automated summary

The study explores the difference in topology-structure-conformation relationship between linear and cyclic graft polymers, showing that cyclic graft polymers exhibit more compact conformation and suppress interchain association compared to linear graft polymers.