Cloud point suppression in dilute solutions of model gradient copolymers with prespecified composition profiles

Gradient copolymers of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) having prescribed linear, parabolic, and hyperbolic composition profiles were synthesized with the guidance of a numerical model that determines the instantaneous comonomer feed rate. These materials exhibit low polydispersity indices (<1.1); the evolution of the overall DMAEMA content and the absolute molecular weight of the copolymers are all in good agreement with the quantities predicted by our model. Compared to random copolymers of HEMA and DMAEMA, the cloud points of dilute buffered aqueous solutions of gradient copolymers decrease with increasing gradient strength; where the gradient strength is defined as the largest difference in the instantaneous composition along the copolymer. The temperature range over which the solutions transition from transparent to turbid also broadens significantly with increasing gradient strength. Both observations suggest the onset of transition to be dictated by the least soluble ends of the polymer chains. These correlations point to the importance of monomer sequence distribution in determining the macroscopic physical properties of copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 The details of monomer sequence distribution can alter the macroscopic properties of copolymers dramatically. Dilute aqueous solutions comprising gradient copolymers having prespecified linear composition profiles, targeted overall compositions and molecular weights, as well as and narrow molecular weight distributions exhibit suppressed cloud points compared to those of random copolymers having comparable compositions and molecular weights. Consistent with a reel-in model, the cloud point transitions of gradient copolymer solutions are also significantly broader than the cloud point transitions of random copolymers.