Linear gradient copolymer melt brushes

The influence of gradient and statistical arrangements of guanidinium or primary amine groups in poly(methacrylate) copolymers on their DNA binding affinity

Herein, we report the first gradient guanidinium containing cationic copolymers and investigate their binding ability to plasmid DNA (pDNA).

Gradient and block side-chain liquid crystalline polyethers

Synthesis of gradient liquid crystalline copolymers is reported for the first time, phase structures of which on multiple length scales with composition and temperature are investigated and compared with the corresponding diblock copolymers.

Swelling of chemical and physical planar brushes of gradient copolymers in a selective solvent

We propose a mean-field theory of chemical and physical planar brushes of linear gradient copolymers swollen in a selective solvent. The polymer chains are grafted to the substrate by the ends with the excess of insoluble monomer units, and the majority of the soluble units are located near the free ends of the chains. The grafting points are considered to be immobile (chemical brush) and mobile in-plane (physical brush). In the latter case the grafting density is determined from the equilibrium conditions (minimum of the free energy). A common peculiarity of the brushes of both types is that the polymer concentration gradually changes from a relatively high value near the substrate (collapsed region of the brush) to a small value near the free surface (swollen region of the brush). In the case of the chemical brush, a polymer depletion zone can appear in the middle of the brush if incompatibility between insoluble and soluble (A and B) units is high enough. Here the polymer density is even lower than near the free surface of the brush. The grafting density of the physical brush is inversely proportional to the chain length and increases with the decrease of the solvent quality for the insoluble (A) units. The latter can be accompanied by shrinkage of the brush thickness due to broad distribution of the insoluble units through the chain: a minor fraction of insoluble units near the free ends can aggregate with a major fraction of them near the substrate. As a result, the concentration of the soluble (B) units can have a maximum in the middle of the brush rather than near the free surface.

pH Responsivity and micelle formation of gradient copolymers of methacrylic acid and methyl methacrylate in aqueous solution

A series of gradient copolymers of methacrylic acid (MAA)/methyl methacrylate (MMA) with four end-to-end composition profiles (uniform, linear gradient, triblock with linear gradient midblock, and diblock) but all having an average chain composition of ̅F(MMA) ≈ 0.5 and an average chain length of 200 were synthesized via model-based, computer-programmed, semibatch atom-transfer radical copolymerization (ATRcoP). These samples allowed us to investigate systematically the effects of the gradient composition profile on the pH responsivity and micelle formation of the copolymers in an aqueous solution. Measurements included light transmittance, TEM, AFM, DLS, (1)H NMR, and pH titration. It was found that linear gradient, triblock, and diblock copolymers formed spherical micelles at high pH. The micelles of the linear gradient copolymer contained MMA units in their hydrophilic shells, and those of the triblock and diblock copolymers had all of their MMA units residing in their cores. The composition profile showed a strong effect on the degree of acid dissociation at a given pH. The conformational transition of the copolymer chains was determined by both the pH value and composition profile. Copolymers having sharper gradients required a lower pH to trigger the conformational transition and a narrower pH range to complete the transition.