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

Impact of surfactant raw material variability on extrudate clarity appearance (transparency) in HME continuous manufacturing

The appearance of an extrudate formulation was monitored during hot-melt extrusion (HME) continuous manufacturing over 3 days. The formulation matrix consisted of a polymeric component, copovidone, and a low molecular weight surfactant, polysorbate 80. Based on studies prior to the continuous manufacturing, the desired appearance of the target extrudate is translucent. Although process parameters such as feed rate and screw speed were fixed during the continuous manufacturing, the extrudate appearance changed over time from turbid to translucent. For root-cause investigation, the extrudates were analyzed offline by differential scanning calorimetry (DSC) and advanced polymer chromatography (APC™). Although the polysorbate 80 content of both turbid and translucent extrudates was within target, the glass transition temperature of the turbid extrudate was 2 °C above expected value. The observed turbidity was traced to lot-to-lot variability of the polysorbate 80 used in the continuous manufacturing, where APC™ analysis revealed that the relative content of the low molecular weight component varied from 23% to 27% in correlation with the evolution from turbid to translucent extrudates. This work stresses the importance of taking feeding material variability into account during continuous manufacturing.

Polymers and Composites Derived from Castor Oil as Sustainable Materials and Degradable Biomaterials: Current Status and Emerging Trends

Recent years have seen rapid growth in utilizing vegetable oils to derive a wide variety of polymers to replace petroleum-based polymers for minimizing environmental impact. Nonedible castor oil (CO) can be extracted from castor plants that grow easily, even in an arid land. CO is a promising source for developing several polymers such as polyurethanes, polyesters, polyamides, and epoxy-polymers. Several synthesis routes have been developed, and distinct properties of polymers have been studied for industrial applications. Furthermore, fillers and fibers, including nanomaterials, have been incorporated in these polymers for enhancing their physical, thermal, and mechanical properties. This review highlights the development of CO-based polymers and their composites with attractive properties for industrial and biomedical applications. Recent advancements in CO-based polymers and their composites are presented along with a discussion on future opportunities for further developments in diverse applications.

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.

Chain Conformation of Water-Insoluble Hyperbranched Polysaccharide from Fungus

Water-insoluble polysaccharide (TM3a), extracted from sclerotia of Pleurotus tuber-regium, was identified as a hyperbranched beta-d-glucan from the results of one- and two-dimensional NMR and GC-MS analysis. The degree of branching of TM3a is 65.5%. TM3a was fractionated by using a non-solvent addition method into 14 fractions, and its solution properties in 0.25 M LiCl/dimethylsulfoxide (DMSO) solution were studied systematically by using static laser light scattering, dynamic light scattering, and viscometry at 25 degrees C. The dependences among the values of intrinsic viscosity ([eta]), radius of gyration (<S2>z 1/2), and hydradynamic radius (Rh) on weight-average molecular weight (Mw) were found as the following: [eta] = 0.46Mw0.30+/-0.01, <S2>z 1/2 = 4.79 x 10-2Mw0.43+/-0.04, and Rh = 5.01 x 10-2Mw0.41+/-0.02 in the Mw range from 1.94 x 105 to 2.06 x 107 for TM3a in a 0.25 M LiCl/DMSO solution at 25 degrees C. The current theory of polymer solution was applied to explain the relationship among the fractal dimension, ratio of geometric to hydrodynamic radius (rho = <S2>z 1/2/Rh), and MwA2/[eta] of TM3a. The results indicated that TM3a existed as a compact chain conformation with a sphere-like structure in LiCl/DMSO solution. Furthermore, by using transmission electron microscopy, we observed directly the spherical molecules with an average diameter of 23.0 +/- 1.8 nm.

Hydrogel-elastomer composite biomaterials: 2. Effects of aging methacrylated gelatin solutions on the preparation and physical properties of interpenetrating polymer networks

This study was conducted to understand the effects of aging methacrylated gelatin solutions on the properties of gelatin-HydroThane Interpenetrating Polymer Network (IPN) films. The latter were prepared from methacrylated gelatin solutions that were either freshly made or stored at different concentrations and temperatures for various periods. The morphology, swelling stability and mechanical properties of the IPNs were then accordingly characterized. The IPNs prepared with aged solutions showed a reduced phase separation; changed from a network-like structure to a continuous phase structure; and demonstrated higher swelling stabilities and higher elasticity under optimal aging conditions, compared to the IPN prepared with a fresh methacrylated gelatin solution. An increase in viscosity and a change in phase transition of aged methacrylated gelatin solutions were also observed, presumably due to the physical structuring of methacrylated gelatin chains (e.g., by the formation of a helix structure), thus altering the resulting IPN characteristics. A better understanding of the effects of aging methacrylated gelatin solution on the formation and properties of gelatin-HydroThane IPNs should enable us to further develop our composite biomaterials for different dressing applications.

Effects of Ethyl and Benzyl Groups on the Miscibility and Properties of Castor Oil-Based Polyurethane/Starch Derivative Semi-Interpenetrating Polymer Networks

Cornstarch derivative (ES), prepared using diethyl sulfate as an etherifying reagent, was blended with castor oil-based polyurethane (PU) prepolymer to obtain a series of semi-interpenetrating polymer network (semi-IPN) materials, named as UES films. Simultaneously, other kinds of semi-IPN (UBS2) were prepared from PU and benzyl starch (BS2) to compare the effects of the substitute groups. The differences in the miscibility and properties of the two series of materials were investigated using attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, dynamic mechanical thermal analysis, ultraviolet-visible spectroscopy, water-sensitivity and tensile testing. The experimental results revealed that UBS2 films exhibit stronger interfacial attraction and better phase mixing than the UES films, as a result of specific interactions between the PU hard segments and BS2 phenyl groups. The optical transmittance, water-resistivity, tensile strength, and elongation at break of the UBS2 films were clearly higher than those of the UES films containing the same concentration of PU. In particular, the miscibility and properties of the UES film with 40 wt.-% ES, were very poor, whereas the semi-IPN films containing 70 wt.-% benzyl starch still had a certain miscibility and good properties. Therefore, the phenyl groups play an important role in the improvement of the miscibility and properties of the semi-IPN materials.