Gradient‐IPN‐modified hydrogel beads: Their synthesis by diffusion–polycondensation and function as controlled drug delivery agents

Abstract

SynopsisInterpenetrating polymer network (IPN) membranes and gradient-IPN polymers were synthesized by immersing crosslinked, 2-hydroxyethylmethacrylate copolymer beads which were swollen in polyol in solutions of diisocyanates. Diffusion of reactants and polycondensation take place simultaneously, and the polymer beads are modified by a polyurethane-IPN layer whose thickness and compositional gradient are a function of reaction rate and diffusion rate. When the reaction is fast relative to diffusion, the reaction zone is narrow and the IPN boundary layer is sharp, whereas when diffusion dominates, the reaction zone and the IPN-modified region becomes broader and more diffuse. A water-soluble drug imbibed into such gradient-IPN-modified hydrogel beads is released over a prolonged time period due to the less permeable IPN barrier and because of a drug-distribution gradient in the polymer, which follows the polyurethane gradient. Diffusion polycondensation can be considered a special case of interfacial polycondensation, one in which the interface area is expanded into and stabilized by a preformed polymer matrix, which serves as reaction medium.

Releasing property from surface polyion complex gel

“…Gradient structures on hydrogels have attracted much attention. The simple preparation of an interpenetrating polymer network and the concentration of the crosslinker have been investigated for hydrogels with a gradient density of networks. The surface condition of the hydrogel preparation also has a great influence on the physical characteristics .…”

Synthesis and characterization of styrene‐butyl acrylate polymers, varying feed composition in a semicontinuous emulsion process

“…16 The gradient composition concept has been also applied in small beads prepared by suspension polymerization, to release, in a controlled way, a pharmaceutical drug over a prolonged time, due to the drugdistribution gradient. 17 Looking at particle level, in seeded emulsion polymerizations (SEPs), seed latices have been used to prepare two-component materials in two-stage processes, pursuing properties combination. In such processes, as a consequence of the incompatibility between polymer components, two-phase particles are usually obtained.…”

Gradient Structure Polymer Obtained from a Homogeneous Mixture: Synthesis and Mechanical Properties

“…The main advantage of such gradient polymers is the possibility, because of their spatial gradient, of making polymer systems with customized properties for different applications. [2][3][4][5][6][7][8][9][10][11] Recently, a new method to create gradient materials has been developed. [12,13] Compared to what is usually encountered in the literature, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] the originality of this method relies on the fact that it does not make use of a mixture containing at least one polymer, but it involves a photopolymerization reaction of a homogeneous system, that is to say a system of monomers and oligomers.…”