Cationic Poly(N-isopropylacrylamide) Block Copolymer Adsorption Investigated by Dual Polarization Interferometry and Lattice Mean–Field Theory

Abstract

A series of cationic diblock copolymers, poly(N-isopropylacrylamide)(48)-block-poly((3-acrylamidopropyl)trimethylammonium chloride)(X), abbreviated as PNIPAAM(48)-b-PAMPTMA(+)(X) (X = 0, 6, 10, 14, and 20), has been synthesized, and their adsorption onto silicon oxynitride from aqueous solution has been investigated using dual polarization interferometry. The polymer adsorption was modeled by using a lattice mean-field theory, and a satisfactory consistency between theory and experiments was found in terms of surface excess and layer thickness. Both theory and experiments show that the adsorption is limited by steric repulsion for X < X(max) and by electrostatic interactions for X > X(max). Modeling demonstrates that significant surface charge regulation occurs due to adsorption. Both the nonionic and cationic block exhibit nonelectrostatic affinity to silicon oxynitride and thus contribute to the driving force for adsorption, and modeling is used for clarifying how changes in the nonelectrostatic affinity affects the surface excess. The segments of the nonionic and cationic blocks seem less segregated when both have a nonelectrostatic affinity for the surface compared to the case where the segments had no surface affinity. Adsorption kinetics was investigated experimentally. Two kinetic regimes were observed: the adsorption rate is initially controlled by the mass transfer rate to the surface and at higher coverage is limited by the attachment rate.

Thermo-responsive diblock and triblock cationic copolymers at the silica/aqueous interface: A QCM-D and AFM study

“…The PAMPTMA block of the copolymers is positively charged in aqueous solution, thus can electrostatically adsorb onto negatively charged surfaces such as silica. [44][45][46] This feature can be employed to produce stable polymer layers, which can be used in various practical applications, e.g., to prevent adhesion of biomolecules or conversely to promote specific attachment of cell types to surfaces. [47][48][49] Dynamic light scattering (DLS) is employed to inquire the thermo-responsive behavior and hydrodynamic size of the copolymers in bulk aqueous solution.…”

Synthesis of cationic poly((3-acrylamidopropyl)trimethylammonium chloride) by SARA ATRP in ecofriendly solvent mixtures

“…The cationic monomer (3-acrylamidopropyl)trimethylammonium chloride (AMPTMA) has been investigated for various applications. AMPTMA has been included in temperature-responsive copolymers [24][25][26] with potential to be used as drug delivery systems, 27 and as a microcarrier for cell proliferation 28 or in gene delivery. 29,30 The existing protocols for the ATRP of AMPTMA require more than 10 000 ppm of CuCl or CuCl 2 coordinated with Me 6 TREN, in DMF-water mixtures (DMF: dimethylformamide), using ethyl-2-chloropropionate (ECP) as the initiator.…”

“…29,30 The existing protocols for the ATRP of AMPTMA require more than 10 000 ppm of CuCl or CuCl 2 coordinated with Me 6 TREN, in DMF-water mixtures (DMF: dimethylformamide), using ethyl-2-chloropropionate (ECP) as the initiator. [24][25][26][27][28][29][30] To perform these reactions under more ecofriendly conditions, lower catalyst loadings and less toxic solvents are desired.…”

Mechanistic insights into the formation of polyion complex aggregates from cationic thermoresponsive diblock copolymers

“…A limited number of articles describe the synthesis of PAPTAC-b-PNIPAM diblock copolymers and the study of their physicochemical properties, with no focus on their interaction with oppositely charged polymers. [15][16][17][18] Although ATRP of 3acrylamidopropyltrimethylammonium chloride (APTAC) was reported in water-ethanol mixtures, [19] the synthesis of PNIPAM-PAPTAC diblock copolymers by ATRP was only performed in water-DMF (50/50 v/v) at 20 °C. [15][16] In the latter conditions, Patrizi et al first polymerized APTAC using the CuCl/Me6TREN catalyst before adding N-isopropylacrylamide (NIPAM) according to a "one-pot"…”

“…protocol. [15] Nyström and coworkers [16][17][18] slightly modified these conditions by polymerizing NIPAM first with the CuCl/CuCl2/Me6TREN catalyst before chain extension with APTAC polymerization. A more eco-friendly, metal-free approach is reported here by performing the synthesis of PAPTAC-b-PNIPAM diblock copolymers in water at room temperature by means of reversible addition-fragmentation chain transfer (RAFT) polymerization.…”