POSS-induced enhancement of mechanical strength in RAFT-made thermoresponsive hydrogels

Abstract

To understand the effect of polyhedral oligomeric silsesquioxane (POSS) moieties on the rheological properties of thermoresponsive hydrogels, poly(ethylene glycol) methyl ether methacrylate (PEGMA) based gels have been synthesized via conventional free radical polymerization (FRP) and reversible additionfragmentation chain transfer (RAFT) polymerization techniques. Two different chain transfer agents (CTAs), namely 4-cyano-4-(dodecylsulfanylthiocarbonyl) sulfanylpentanoic acid (CDP) and a POSS chainended CTA (POSS-CDP) have been employed for the RAFT polymerization of PEGMA in the presence of a di-functional cross-linker, di(ethylene glycol) dimethacrylate (DEGDMA). Swelling, deswelling and reswelling behaviors due to the introduction of the POSS moiety have been systematically examined and compared with the CDP based hydrogels at similar compositions. The surface topology and structural porosity of the hydrogel matrix are examined by field emission-scanning electron microscopy (FE-SEM). The mechanical behavior of the swollen hydrogels has been investigated through rheological measurements.Interestingly, we find that the mechanical stability of the hydrogels improved by increasing both the cross-linking density and total net fraction of the POSS moieties.

Biodegradable Inorganic–Organic POSS–PEG Hybrid Hydrogels as Scaffolds for Tissue Engineering

“…Polyhedral oligomeric silsequioxanes (POSS), with a special cage-shaped structure formed by rigid SiO bonds and eight organic corner groups to the vertexes of the cage, are a family of inorganic-organic hybrid materials. [16][17][18][19] Their functional arms create the opportunity for reacting with other polymers via covalent bonding. A number of POSS-based hybrid biomaterials with tunable mechanical stabilities have been prepared by copolymerizing POSS into polymer matrix since POSS macromers exhibit enhanced mechanical stability and be used for biomedical application.…”

“…Polyhedral oligomeric silsequioxanes (POSS), with a special cage‐shaped structure formed by rigid SiO bonds and eight organic corner groups to the vertexes of the cage, are a family of inorganic–organic hybrid materials . Their functional arms create the opportunity for reacting with other polymers via covalent bonding.…”

Preparation of a Salecan/poly(2‐acrylamido‐2‐methylpropanosulfonic acid‐co‐[2‐(methacryloxy)ethyl]trimethylammonium chloride) Semi‐IPN Hydrogel for Drug Delivery

“…For example, SPAM1 released over 89.4 % of its absorbed water after 600 min, whereas during identical time intervals SPAM2, SPAM3, and SPAM4 lost about 92.7, 95.6, and 98.5 % of their water, respectively. Such an improvement in water retention might be ascribed to the fact that the addition of hydrophilic polysaccharides (i.e., salecan), which can act as water‐releasing channels upon gel shrinkage, facilitates the removal of water …”

Aliphatic Polyester/polyhedral Oligomeric Silsesquioxanes Hybrid Networks via Copper‐free 1,3‐dipolar Cycloaddition Click Reaction

“…The sample specimens were molded into rectangular bars with 1 mm × 10 mm × 50 mm dimensions. The swelling ratio of hybrid networks with various protic and aprotic solvents such as acetonitrile, chloroform, N,N ‐dimethylformamide, dimethyl sulfoxide, 1,4‐dioxane, hexane, methanol, tetrahydrofuran, and toluene were measured by gravimetric analysis, a small piece of hybrid network was taken in a 25 mL beaker and immersed in solvent at 22 °C for 48 h to attain the maximum swelling ratio . Then, the swollen hybrid network was taken out carefully from the beaker, wiped with blotting paper to remove the surface solvent and weighed on a dry Petri dish.…”

“…The swelling ratio of hybrid networks with various protic and aprotic solvents such as acetonitrile, chloroform, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, hexane, methanol, tetrahydrofuran, and toluene were measured by gravimetric analysis, a small piece of hybrid network was taken in a 25 mL beaker and immersed in solvent at 22 C for 48 h to attain the maximum swelling ratio. 46 Then, the swollen hybrid network was taken out carefully from the beaker, wiped with blotting paper to remove the surface solvent and weighed on a dry Petri dish. This value was calculated by following equation: Swelling ratio (SR HN ) = (W t -W d )/W d where W t was the weight of the swollen hybrid network at time 48 h and W d was the weight of the dry hybrid network.…”