Preparation of acrylamide‐based poly‐HIPEs with enhanced mechanical strength using PVDBM‐b‐PEG‐emulsified CO₂‐in‐water emulsions

Abstract

Poly(vinyl acetate-alt-dibutyl maleate)-block-poly(ethylene glycol) (PVDBM-b-PEG) copolymers were synthesized via reversible addition-fragmentation chain transfer radical polymerization and used as emulsifiers to form stable CO 2 -in-water high internal phase emulsions (C/W HIPEs). Then, highly interconnected cellular polyacrylamide (PAM) and poly(acrylamide-co-N-hydroxymethyl acrylamide) [P(AM-co-HMAM)] poly-HIPEs with enhanced mechanical strength were prepared based on the stable C/W HIPEs. The porous structures of the PAM poly-HIPEs, as well as morphology and compressive modulus, could be influenced by the surfactant concentration and the length of the CO 2 -philic tails of the surfactants. PAM poly-HIPEs with the smallest average pore diameter (11.12 6 0.62 lm) and the highest compressive modulus (22.65 6 0.10 MPa) could be obtained by using the short CO 2 -philic chains of the PVDBM-b-PEG surfactant at a high concentration (1.0 wt %). Moreover, with the copolymerization of N-hydroxymethyl acrylamide (HMAM) comonomers with acrylamide, the compressive modulus of the obtained P(AM-co-HMAM) poly-HIPEs was three times higher than that of PAM poly-HIPEs. Both PAM and P(AM-co-HMAM) poly-HIPEs were employed as scaffolds to guide H9c2 cardiac muscle cellular growth. Fluorescence images showed that a smaller average pore size and a narrower pore-size distribution were helpful for cell growth and proliferation on these materials. INTRODUCTIONHigh internal phase emulsions (HIPEs, internal phase volume >74.05%) are of great interest in the synthesis of porous organic polymers (poly-HIPEs) by polymerizing the monomers dissolved in the external phase. 1 Removing the internal phase of HIPEs gives poly-HIPEs an open-cell and highly interconnected pore network structure. 2 Due to their advantages of high permeability, uniform cellular structure, easy preparation, and facile control of pore size, poly-HIPEs have been widely discussed as supports for catalysts, 3-5 scaffolds for cell culture, 6,7 and separation media 8 over the last several decades. Poly-HIPEs can be prepared from different HIPEs, such as water-in-oil (W/O) HIPEs, oil-in-water (O/W) HIPEs, and CO 2 -in-water (C/W) HIPEs. 9-11 Among these HIPEs, the C/W HIPE templating method is a green and facile approach, where the internal phase (CO 2 ) can be easily removed by simply depressuring the system. Meanwhile, no volatile organic compounds (VOCs) are used in the process, which makes it suitable for the synthesis of biocompatible materials like cell scaffolds. As we know, the porosity, interconnectivity, and pore size can significantly affect the transport issues of cell scaffolds, including cell migration, nutrient delivery, waste removal, and exclusion of materials or cells. 12 Nevertheless, CO 2 has a poor capability for dissolving most polar and macromolecular substances because of its weak polarity. The design of effective surfactants is a key factor in the formation of stable C/W emulsions as well as polymerization of C/W HIPEs. 13 In this regard, many research...

Natural hydrogels for cartilage regeneration: Modification, preparation and application

“…The compressive strength of the hydrogel scaffolds consists of alginate, chitosan, polyvinyl alcohol or hyaluronan that can range from 0.46 to 5.64 MPa [3], [4], [5]. However, the hydrogels made by artificial polymers, such as polylactic-co-glycolic acid (PLGA), polymethyl methacrylate (PMMA), polycaprolactone (PCL) and poly(ethylene glycol) (PEG) can achieve the mechanical strength of ≥20–120 MPa [6], [7], [8]. The natural and synthetic polymers can be prepared using polymeric blending to achieve hydrogels for diverse application in biomedical fields, thereby allowing the adjustment of the physical and chemical properties of both kinds of polymers [9].…”