Hydrogels are interesting as wound dressing for burn wounds to maintain a moist environment. Especially gelatin and alginate based wound dressings show strong potential. Both polymers are modified by introducing photocrosslinkable functionalities and combined to hydrogel films (gel‐MA/alg‐MA). In one protocol gel‐MA films are incubated in alg‐MA solutions and crosslinked afterward into double networks. Another protocol involves blending both and subsequent photocrosslinking. The introduction of alginate into the gelatin matrix results in phase separation with polysaccharide microdomains in a protein matrix. Addition of alg(‐MA) to gel‐MA leads to an increased swelling compared to 100% gelatin and similar to the commercial Aquacel Ag dressing. In vitro tests show better cell adhesion for films which have a lower alginate content and also have superior mechanical properties. The hydrogel dressings exhibit good biocompatibility with adaptable cell attachment properties. An adequate gelatin‐alginate ratio should allow application of the materials as wound dressings for several days without tissue ingrowth.
Polysaccharides, and especially alginate, can be useful for self-healing of cracks in concrete. Instead of weak electrostatic bonds present within calcium alginate, covalent bonds, by methacrylation of the polysaccharides, will result in mechanically stronger superabsorbent polymers (SAPs). These methacrylated alginate chains as backbone are combined with two acrylic monomers in a varying molar fraction. These SAPs show a moisture uptake capacity up to 110% their own weight at a relative humidity of 95%, with a negligible hysteresis. The swelling capacity increased (up to 246 times its own weight) with a decreasing acrylic acid/2 acrylamido-2-methylpropane sulfonic acid ratio. The SAPs also showed a thermal stability up to 200°C. Interestingly, the SAP composed of alginate and acrylic acid exerted a very limited decrease in compressive strength (up to 7% with addition of 1wt% SAP) rendering this material interesting for the envisaged self-healing application.
In the present contribution, we report the MADIX/RAFT polymerization for the synthesis of thermoresponsive homo and statistical copolymers of N-vinylcaprolactam (NVCL) and N-vinylpyrrolidone (NVP). The conditions for the polymerization of NVP were optimized using an automated parallel synthesizer and these optimal conditions were applied for preparing copolymers with systematical variation in composition. The cloud point temperatures (T-CP's) of aqueous solutions of PNVCL and P(NVCL-stat-NVP)'s (CP1-CP5) were found to be tuneable between 40 degrees C and >95 degrees C at 5 mg mL(-1). Next, stable colloidal solutions of AuNPs coated with PNVCL and CP1-CP5 were obtained via an exchange reaction of pre-synthesized citrate stabilized AuNPs with PNVCL and CP1-CP5 by a direct 'grafting to' approach. The maximum absorbance wavelength (lambda(max)) of the surface plasmon resonance (SPR) band and size of all the thermoresponsive polymer coated AuNPs were found to be almost unchanged up to 65 degrees C (above the T-CP of PNVCL and CP5) in MilliQ water which is presumably due to electrostatic stabilization of the AuNPs by residual citrate groups on the surface. However, in 0.1 M NaCl aqueous solution the lambda(max) of the thermoresponsive AuNPs were red shifted when heated up to 65 degrees C which is attributed to the screening of the citrate negative charges on the surface of AuNPs that suppress electrostatic stabilization enabling T-induced aggregation leading to a shift in the SPR band. These thermoresponsive AuNPs may find applications as colorimetric temperature and/or salt sensors
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