Tricomponent thermoresponsive polymers based on an amine-containing monomer with tuneable hydrophobicity: Effect of composition

Abstract

In the present study, six dual-responsive ABC triblock copolymers were synthesised via group transfer polymerisation (GTP) and investigated through visual inspections in terms of their thermoresponsive behaviour. The copolymers consist of i) penta(ethylene glycol) methyl ether methacrylate (PEGMA), which is hydrophilic and thermoresponsive at high temperatures, ii) n-butyl methacrylate (BuMA) as the hydrophobic counterpart to promote self-assembly, and iii) 2-(diethylamino)ethyl methacrylate (DEAEMA), which is pH-responsive by adjusting its hydrophilicity depending on the pH. The effect of the degree of ionisation of DEAEMA units as well as the ionic strength effect on the self-assembly behaviour of the copolymers was tested via dynamic light scattering (DLS). The dissociation constants (pKa) of the amine units of DEAEMA were determined via potentiometric titrations. The thermoresponse has been primarily been investigated in means of cloud points (CPs) at various pH values in deionised water. Detailed phase diagrams were constructed for all the polymer solutions in phosphate buffered saline (PBS), with the interest being focused on the gelation area. It has been clearly proven that gelation is promoted as the content in BuMA and DEAEMA is increased. The polymer that presented the widest gelation area has been further investigated via rheology in terms of its gelation temperature, gelation time and shear-thinning properties.

A library of thermoresponsive PEG‐based methacrylate homopolymers: How do the molar mass and number of ethylene glycol groups affect the cloud point?

“…As shown in Table 1, the MMDs of these homopolymers were all lower than 1.21 similar to previous GTP polymerizations using PEG based methacrylates, indicating a successful polymerization. 36,42,45,53,54,[56][57][58] The MMDs of PEGMA and NEGMA polymers were slightly higher than others which agreed with previous studies. The first reason was the PEGMA and NEGMA are macromonomers with an average MM.…”

“…The effective pK a s of the DMAEMA homopolymers were determined and were in the range of 7.2-7.3 which agreed with previously reported pK a values of DMAEMA polymers. 36,42,44,53,54,[56][57][58]…”

How does the hydrophobic content of methacrylate ABA triblock copolymers affect polymersome formation?

“…The polymers were synthesized by group transfer polymerization (GTP), a living polymerization method ideal for the fabrication of methacrylate block polymers on large scales. [40][41][42] The two monomers used were: a PEG-based monomer, specifically, the triethylene glycol methyl ether methacrylate (TEGMA) and the pH responsive DEA-EMA 28 which is normally hydrophobic at physiological conditions (pH 7.4). The hydrophilic and nonionic monomer TEGMA forms the A block while the hydrophobic DEAEMA is the B block and thus, these ABA amphiphilic polymers can self-assemble into polymersomes or micelles.…”

“…In total, five ABA polymers were synthesized, with the Đ smaller than 1.32, which is adequate for polymers made via GTP when using a PEG-based methacrylate macromonomer. 28,[43][44][45][46][47][48][49] A narrow Đ is critical in this study to be able to carry out a systematic investigation. 50 The illustration of the sequential polymerization reaction is shown in Figure 1.…”

“…Specifically the pH responsive hydrophobic block was based on 2-(diethylamino) ethyl methacrylate (DEAEMA). 28 Several polymersomes or polymer vesicles studies used DEAEMA containing polymers. 25,[29][30][31][32][33][34][35][36][37][38][39] These studies were either on AB diblocks 25,30,32,[34][35][36][37][38] or ABC block copolymers.…”