Effect of molecular weight and molecular architecture of PMMA on the phase morphology of pseudo-IPN's of PCU/PMMA

Hydrogel-elastomer composite biomaterials: 3. Effects of gelatin molecular weight and type on the preparation and physical properties of interpenetrating polymer networks

To optimize the preparation of a gelatin-HydroThane Interpenetrating Polymer Network (IPN) and obtain optimum physical properties for its use as a wound dressing, we studied IPN films prepared with two types of gelatin having different molecular weights. The effects of the gelatin molecular weight and type on the IPN film's structure, morphology, swelling and mechanical properties were determined. While FTIR did not reveal any noticeable differences between the IPNs prepared using different gelatin, light microscopy showed a lesser phase separation of the film prepared with a high-molecular-weight type A gelatin. Furthermore, these films displayed slightly less swelling, higher strength and lower strain, compared to the IPNs prepared with either low-molecular-weight type A or type B gelatin. The IPN prepared with type B gelatin showed higher swelling in serum-containing medium than those prepared with type A gelatin, because of its ionic charges under the condition. Increases in viscosity were observed with increasing molecular weight, type A being more viscous than type B gelatin despite having a lower bloom number. The viscosity of the high-molecular-weight gelatin was in the same magnitude as that of HydroThane, which might lead to less phase separation. A better understanding of the effects of alterations in the gelatin molecular weight and type on the formation and properties of the gelatin-HydroThane IPN should facilitate the development of promising composite biomaterials for wound dressing applications.

Effects of Molecular Weight on the Miscibility and Properties of Polyurethane/Benzyl Starch Semi-Interpenetrating Polymer Networks

We successfully prepared a series of semi-interpenetrating polymer networks (semi-IPNs) from castor oil-based polyurethane (PU) and 20 wt % benzyl starch (BS) with different weight-average molecular weights (M(w)), coded as the PU/BS films. The M(w) values of a series of BSs were determined by size-exclusion chromatography combined with laser light scattering. The effects of the BS M(w) on the miscibility and properties of the resulting PU/BS films were investigated using reflection Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, scanning electron microscopy, optical microscopy, ultraviolet-visible spectroscopy, and tensile testing. The results revealed that the PU/BS films possessed much higher optical transmittance and tensile strength than the pure PU film. Interestingly, with a decrease of the BS M(w) from 1.69 x 10(7) to 5.70 x 10(5), the optical transmittance, tensile strength, and elongation at break of the PU/BS films increased from 82% to 89%, from 11.7 to 15.7 MPa, and from 121% to 180%, respectively. Therefore, the M(w) of BS plays an important role in the improvement of the miscibility and properties of the semi-IPN materials. On the basis of the analysis of the miscibility and the morphology of the PU/BS films, the interaction between the PU and the BS with relatively low M(w) was stronger than that with high M(w).