Porous carboxymethylcellulose/polyethyleneimine composite beads: formation process, enhanced physical properties, and pH-induced response mechanism

Abstract

Carboxymethylcellulose (CMC) composite beads formed by physicochemical crosslinking have emerged as functional biomaterials. However, the effects of the crosslinker dosage on the structure and properties of these beads have not been thoroughly examined. In this study, robust CMC composite beads with porous channel structures were synthesized via a dropping method and acetic acid solidification after physicochemical crosslinking with (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and polyethylenimine (PEI). The influence of the PEI dosage on the physicochemical, structural, and physical properties of the produced CMC/GPTMS/PEI beads (CGPBs) was investigated. The physical properties of wet CGPBs were evaluated by conducting rheological tests, such as strain/frequency sweep and creep/recovery tests. With increasing PEI dosage, more PEI species effectively reacted with CMC and GPTMS molecules through multiple physicochemical interactions (covalent/ionic/hydrogen bonds) to increase the channel width, channel wall thickness, nanopore size, and CGPB porosity and improve the mechanical properties of wet CGPBs, such as yield stress, storage modulus, and resistance to deformation. Moreover, CGPBs exhibited pH-induced response behavior, and their swelling/shrinkage and mechanical stability were strongly affected by the solution pH. This study establishes a relationship between the PEI dosage and physicochemical, structural, and mechanical properties of CGPBs, providing theoretical guidance for the design of stable CMC composite beads.