Sustainable Thermoplastic Elastomers Derived from Fatty Acids

Abstract

Vegetable oils are an attractive source for polymers due to their low cost, abundance, annual renewability, and ease of functionalization. Stearyl and lauryl acrylate, derived from vegetable oils such as soybean, coconut, and palm kernel oil, have been polymerized through reversible addition−fragmentation chain transfer polymerization, resulting in poly(styrene-b-(lauryl acrylate-co-stearyl acrylate)-b-styrene) (SAS) triblock copolymers. Varying the length of the side chain on the polyacrylate midblock (C18 and C12 in stearyl and lauryl acrylate repeat units, respectively) is a convenient tool for tuning the physical properties of the triblock copolymers. The SAS triblock copolymers exhibit properties appropriate for thermoplastic elastomer (TPE) applications. Small-angle X-ray scattering and transmission electron microscopy experiments have elucidated the microphase-separated morphology of the SAS triblock copolymers, consistent with a spherical morphology lacking long-range order. The physical properties of the polymers can be readily tuned by varying the acrylate midblock composition, including the melting temperature, viscosity, and triblock copolymer tensile properties. Tensile testing reveals elastomeric behavior with high elongation at break. Surprisingly, the order−disorder transition temperature of the triblock copolymer is not dependent on the acrylate composition in the midblock. This indicates that the acrylate composition can be used as a tool to manipulate the physical properties of the triblock copolymers without affecting the order−disorder transition temperature, or processing temperature, of the TPEs.

Sustainable thermoplastic elastomers derived from renewable cellulose, rosin and fatty acids

“…32,60,61 However in our case, the rigid cellulose backbone is less than 1 wt% of the entire gra copolymer. The so PBA or PLMA segment is a majority component with another rigid PDAEMA as a minority component.…”

Close-Packed Spherical Morphology in an ABA Triblock Copolymer Aligned with Large-Amplitude Oscillatory Shear

“…A drastic change in the storage modulus was observed at the T ODT . 75 Prior studies on body-centered cubic spherical diblock copolymers observed a transition from the body-centered cubic phase to disordered spherical micelles, in which the disordered spherical micelles existed at temperatures above the T ODT (in place of the disordered phase) and exhibited a low modulus. 51, 90 In our study, the abrupt decrease in modulus at elevated temperatures suggests a significant change in the morphology at the T ODT , either homogenization of the sample (loss of spherical domains) and/or loss of the bridging chains which impart the elastomeric behavior in a triblock copolymer thermoplastic elastomer.…”

“…75 We attribute the presence of disordered spheres at low temperatures to the sample preparation process, in which the triblock copolymer was compression molded just above the T ODT for 5 min, and then quenched to room temperature (which is below the T g of the polystyrene end-blocks). Following prior literature, 82 the quenching process likely did not provide enough time above the T g of the endblocks for the equilibrium ordered structure to evolve.…”

Thermoplastic Elastomers Based on Block, Graft, and Star Copolymers

“…It was also found that by using a poly[styrene-alt-(maleic anhydride)] (PSM) as a macro-chain-transfer agent in emulsion polymerization for PS-PnBA-PS [67], ultimate stress increased whereas strain at break decreased as the percentage of PSM increased. Another TPE based on PS and poly(lauryl acrylate) was prepared by a solution RAFT polymerization process [68]. Ultimate stress was lower than 1 MPa and strain at break was lower than 280%.…”