Thermoresponsive gels are an exciting class of materials with many bioapplications, like tissue engineering and drug delivery, but they are also used in formulation industry and 3-D printing. For these applications to be feasible, the gelation temperature must be tailored. Here, it is reported how the gelation temperature is affected and can be tailored by varying the architecture of tetrablock terpolymers. Specifically, 15 copolymers based on penta­(ethylene glycol) methyl ether methacrylate (PEGMA, A block), n-butyl methacrylate (BuMA, B block), and the thermoresponsive 2-(dimethyl­amino)­ethyl methacrylate (DMAEMA, C block) were synthesized using group transfer polymerization. Nine tetrablock copolymers of varying architectures, and one triblock copolymer for comparison, with constant molar mass and composition were fabricated. Specifically, the polymers that were investigated are (i) three polymers that contain two A blocks (ABCA, ABAC, and ACAB), (ii) three polymers that contain two B blocks (BACB, BABC, and ABCB), (iii) three polymers that contain two C blocks (CABC, CACB, and ACBC), and (iv) one ABC triblock terpolymer that was synthesized as the control polymer. Then, the five more promising architectures were chosen, and five more polymers with a slightly different composition were synthesized and characterized. Interestingly, it was demonstrated that the block position (architecture) has a significant effect on self-assembly (micelle formation), cloud point, and the rheological and gelling properties of the polymers with two of the tetrablocks showing promise as injectable gels. Specifically, the ACBC terpolymer with 20–30–50 w/w % PEGMA–BuMA–DMAEMA formed gels at at lower concentration but at higher temperatures than the ABC triblock copolymer that was synthesized as a control. On the other hand, the BABC terpolymer with 30–35–45 w/w % PEGMA–BuMA–DMAEMA formed gels at the same concentrations as the ABC triblock control polymer but at lower and more desirable temperatures, slightly below body temperature.

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.

The one-pot syntheses of two pentadeca-(15)-block methacrylate-based amphiphilic copolymers, specifically a bipolymer (AB)7A and a quintopolymer (ABCDE)3, are being reported using a fast and easy to scale up procedure that does not require any intermediate purification steps.

Gold nanoparticles (AuNPs) fabricated via the self-assembly of block copolymers of various architectures.