Novel hybrid magnetic cross-linked enzyme aggregates of phenylalanine ammonia lyase (HM-PAL-CLEAs) were developed by co-aggregation of enzyme aggregates with magnetite nanoparticles and subsequent crosslinking with glutaraldehyde. The HM-PAL-CLEAs can be easily separated from the reaction mixture by using an external magnetic field. Analysis by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) indicated that PAL-CLEAs were inlayed in nanoparticle aggregates. The HM-PAL-CLEAs revealed a broader limit in optimal pH compared to free enzyme and PAL-CLEAs. Although there is no big difference in Km of enzyme in CLEAs and HM-PAL-CLEAs, Vmax of HM-PAL-CLEAs is about 1.75 times higher than that of CLEAs. Compared with free enzyme and PAL-CLEAs, the HM-PAL-CLEAs also exhibited the highest thermal stability, denaturant stability and storage stability. The HM-PAL-CLEAs retained 30% initial activity even after 11 cycles of reuse, whereas PAL-CLEAs retained 35% of its initial activity only after 7 cycles. These results indicated that hybrid magnetic CLEAs technology might be used as a feasible and efficient solution for improving properties of immobilized enzyme in industrial application.

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Castor oil and microcrystalline cellulose were employed as biomass feedstock to produce bio-based polymer composites with increased tensile strength. The polymer composites were prepared by curing castor oil with 4,4'-methylenebis (phenyl isocyanate) (MDI) in the presence of microcrystalline cellulose (MC) or modified MC (MMC). The MMC was prepared by reacting MDI with MC to introduce isocyanate groups to the surface of MC. X-ray diffraction spectra suggested the good retention of the crystalline structure of MC or MMC in the composites. SEM analysis showed the well dispersion of MC or MMC in the composites. All of these factors are critical to reinforcing the composites. Mechanical tests of the composites revealed that the reinforcing effect of MMC was more significant than MC at high cellulose content such that the highest tensile strengths of 4.87 MPa was obtained for the composite containing 43% (wt) of MMC. That is almost 5 times higher than that of neat castor oil-based polyurethane.

A variety of castor oil-based cationic polyurethane dispersions (PUDs) were synthesized. The effects of hard segment content on the properties of PUDs and the resulting polyurethane films were investigated by mastersizer, Fourier transform infrared (IR), thermal gravimetric analysis (TGA) and stress-strain test. As the hard segment content increased from 37.1 to 45.6 wt %, the particle size of the PUDs increased from 10 to 190 nm. IR analysis showed that hydrogen bonding between hard segments enhanced with the increase of hard segment content. For this enhancement the films had an increased tensile strength from 2.0 to 9.4 MPa and an improved glass transition temperature (Tg) from 48oC to 75oC. TGA showed the films were thermally stable up to 200oC and had biphasic degradation at around 330oC and 440oC. The versatile castor oil-based cationic waterborne polyurethanes are promising in applications as adhesives and coatings.