Multiblock copolymers (MBCPs) are an emerging class of materials that are becoming more accessible in recent years. However, to date there is still a lack of fundamental understanding of their physical properties. In particular, the glass transition temperature (Tg) which is known to be affected by the phase separation has not been well characterized experimentally. To this end, we report the first experimental study on the evolution of the Tgs and the corresponding phase separation of linear MBCPs with increasing number of blocks while keeping the overall degree of polymerization (DP) constant (DP = 200). Ethylene glycol methyl ether acrylate (EGMEA) and tert-butyl acrylate (tBA) were chosen as monomers for reversible addition-fragmentation chain transfer polymerization to synthesize MBCPs. We found the Tgs (as measured by differential scanning calorimetry) of EGMEA and tBA segments within the MCBPs to converge with increasing number of blocks and decreasing block length, correlating with the loss of the heterogeneity as observed from small-angle X-ray scattering (SAXS) analysis. The Tgs of the multiblock copolymers were also compared to the Tgs of the polymer blends of the corresponding homopolymers, and we found that Tgs of the polymer blends were similar to those of the respective homopolymers, as expected. SAXS experiments further demonstrated microphase separation of multiblock copolymers. This work demonstrates the enormous potential of multiblock architectures to tune the physical properties of synthetic polymers, by changing their glass transition temperature and their morphologies obtained from microphase separation, with domain sizes reaching under 10 nm.
Bibliographical noteCopyright: 2017 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolecules , copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/acs.macromol.7b01831.
Funding: German Research Foundation (DFG, GZ: HA 7725/1-1) Thuringian Ministry of Science, Education, and Culture (TMBWK; Grant B515-11028).
Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/F500378/1 through the Molecular Organisation and Assembly in Cells Doctoral Training Centre (MOAC-DTC).
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 704459.