The innovation engine for new materials

Trenton Koeper

Trenton Koeper


Mechanical Engineering


University of California, Santa Barbara


Joshua Lequieu

Faculty Sponsor(s): 

Glenn Fredrickson

Faculty Sponsor's Department(s): 


Project Title: 

Novel Synthetic Rubbers: Using Miktoarms to Improve Phase Behavior

Project Description: 

Thermoplastic elastomers (TPEs) are a widely used type of synthetic rubber, that exhibit similar properties to vulcanized rubber at room temperature, but can be melted and injection molded at high temperatures. The most common TPEs consist of linear triblock copolymers, and are widely used in industry for their combination of strength, elasticity and melt processability. Each of these useful properties are derived from the triblock copolymer’s ability to self-assemble into domains of hard, glassy polymer surrounded by a matrix of elastic polymer. Increasing the volume fraction of glassy polymer increases the strength of the TPE, however when the concentration is increased beyond a certain point, the polymer begins to self assemble into undesirable, brittle structures that lack a continuous elastic domain. Miktoarm star polymers, consisting of one homopolymer arm and multiple diblock arms, have been shown to increase the volume fraction of glassy domains, while maintaining elasticity. In this study we investigated how the number of arms, and the block fraction of the diblock arms of a miktoarm polymer impacts TPE self-assembly. Polymer phase behavior was determined using a computational implementation of self-consistent field theory. We found that both increasing the number of arms, and including asymmetric diblock arms should allow an increase in the volume fraction of glassy domains, while maintaining a continuous elastic phase. These results indicate that TPE strength can be improved by utilizing a miktoarm star polymer architecture with more than three diblock arms, rather than the typical triblock copolymer.