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.
