Interplay of Thermosensitivity and pH Sensitivity of Amphiphilic Block–Gradient Copolymers of Dimethylaminoethyl Acrylate and Styrene

Abstract

Novel pH- and thermoresponsive amphiphilic diblock copolymer, comprising hydrophilic poly­(2-dimethyl­aminoethyl acrylate) (PDMAEA) and amphiphilic poly­(styrene-grad-2-dimethyl­aminoethyl acrylate) (P­(S-grad-DMAEA)) blocks, was synthesized by nitroxide-mediated radical polymerization. A series of copolymers (PS-grad-PDMAEA) with controlled molar masses and low dispersities over a wide range of monomer feed ratios (0 < f S,0 < 1) were synthesized. Both conventional linearization and nonlinear least-squares methods were applied to estimate reliable values of the reactivity ratios for S and DMAEA radical polymerization. The calculated values of the reactivity ratios (r DMAEA = 0.25 and r S = 1.15) perfectly fitted the drift in monomer feed ratio versus conversion, showing a gradient distribution along the copolymer chains. The self-assembling behavior of the copolymers in the aqueous medium was investigated by dynamic light scattering and small-angle neutron scattering over a wide range of pH, temperature, and salt concentration. These block-gradient copolymers show reversible self-association into micelle-like structure (D h ∼ 20 nm) in aqueous solutions triggered by both pH and temperature.

Effect of Hydrophilic Monomer Distribution on Self‐Assembly of a pH‐Responsive Copolymer: Spheres, Worms and Vesicles from a Single Copolymer Composition

“…Diblock and triblock copolymers containing hydrophilic polyacrylic acid and hydrophobic poly(acrylic acid‐ ran ‐butyl acrylate) [22–24] or poly(acrylic acid‐ ran ‐styrene) [25–27] segments show reversible associations across a wide pH range. Copolymers with more complex composition profiles, incorporating hydrophilic homopolymer and moderately hydrophobic gradient copolymer segments may also undergo reversible self‐assembly in response to changes in temperature [28–30] or pH [8, 29] . These results indicate that the incorporation of hydrophilic groups into the hydrophobic segment of an amphiphilic copolymer can have a significant effect on its self‐assembly behavior.…”

“…[5,[9][10][11]15] More recently,a mphiphilic copolymers containing mixed segments (e.g.g radient copolymers and block copolymers with hydrophilic monomers incorporated into the hydrophobic segment) have been shown to form self-assemblies that respond dynamically to changes in their environment. [17,18] Gradient copolymer assemblies may exhibit reversible changes in size [7,19,20] or shape [20,21] in response to changes in solvent quality.D iblock and triblock copolymers containing hydrophilic polyacrylic acid and hydrophobic poly(acrylic acid-ran-butyl acrylate) [22][23][24] or poly(acrylic acid-ran-styrene) [25][26][27] segments show reversible associations across awide pH range.C opolymers with more complex composition profiles,incorporating hydrophilic homopolymer and moderately hydrophobic gradient copolymer segments may also undergo reversible self-assembly in response to changes in temperature [28][29][30] or pH. [8,29] These results indicate that the incorporation of hydrophilic groups into the hydrophobic segment of an amphiphilic copolymer can have as ignificant effect on its self-assembly behavior.…”

Dual stimuli‐responsive polypeptide prepared by thiol‐ene click reaction of poly(l‐cysteine) and N, N‐dimethylaminoethyl acrylate

“…In particular, temperature and pH are two of the most widely used stimuli even tunable in the body environment, which enables innovative approaches to drug delivery, biological diagnostics, and tissue engineering. For example, poly(meth)acrylates including poly(2‐( N , N ‐dimethylamino) ethyl (meth)acrylate) (PDMAE[M]A) and poly[2‐( N , N ‐diethylamino) ethyl methacrylate] (PDEAEMA) have been extensively studied to develop novel carriers that were sensitive to both pH and temperature for controlled drug delivery . Such polymers were generally synthesized from monomers that are weakly basic of a tertiary amine substituted with different alkyl groups.…”

Phase Behavior of Gradient Copolymer Melts with Different Gradient Strengths Revealed by Mesoscale Simulations

“…Linear copolymer chains with various molecular weights and composition profiles (including diblock, triblock or multiblock copolymers; and random, taper or gradient copolymers) are now seen in many industrial applications [2]. Moreover, they are found in environment-sensitive applications, e.g., as bioactive molecular carriers, when used in solution [3][4][5] or self-healing materials [6].…”