A library of thermoresponsive diblock and statistical copolymers: Unravelling the effect of molar mass

Abstract

In the past decades, thermoresponsive polymers have emerged as smart sensing units and promising candidates for a variety of biomedical applications, including targeted drug delivery and tissue engineering. Designing a well-defined thermoresponsive polymer that is versatile for applications requires a systematic study of its properties against its polymeric parameters (i.e., molar mass, composition, and architecture). In terms of the effect of molar mass (MM), previous studies mainly focused on thermoresponsive homopolymers, while the thermoresponsive behaviour of diblock copolymers remained less explored. In this study, we have successfully synthesised 14 different copolymers based on the ionic and thermoresponsive 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) and 14 different copolymers based on the non-ionic and thermoresponsive oligo(ethylene glycol) methyl ether methacrylate with average Mn 300 g mol−1 (OEGMA300) and MMA, in both diblock and statistical forms. Their molar masses were varied from 3000 g mol−1 up to 43 000 g mol−1, and their thermoresponsive and self-assembly behaviours in aqueous solutions were carefully characterised. Intriguingly, DMAEMA-based copolymers demonstrated an increase in cloud point temperature (Tcp) with MM in diblock structures, but a decrease in statistical structures. Conversely, OEGMA300-based copolymers initially exhibit an increase in Tcp as the MM increases, particularly at lower MMs, and then reach a plateau with only slight changes at higher MMs, irrespective of their architecture. This investigation not only explores the impact of MM on these thermoresponsive polymers but also contributes to the future design and application of these comonomers, owing to their wide versatility and established research interest in the biomedical field.