Wenyong Liu

Synthesis and Characterization of Water-Soluble POSS Hybrid Inorganic/Organic PDMAEMA Nanocomposite Hydrogels

A novel POSS hybrid nanocomposite hydrogel was designed and synthesized by introducing water-soluble Oa-POSS into the PDMAEMA hydrogels physically cross-linked by clay. The prepared OaP-NC gels exhibited obvious temperature and pH double responsiveness while the properties and structure of gels depended on the content of added Oa-POSS. The swelling ratio of OaP-NC gels decreased slightly and the deswelling rate raised gradually with the increase of Oa-POSS. Moreover, the tensile strength and resilience of OaP-NC gels was improved significantly. Interestingly, the swelling behavior of gels changed differentially in the drying/reswelling circulation process due to the rearrangement of particles in gels.

Stimulus-responsive hydrogels reinforced by cellulose nanowhisker for controlled drug release

Hybrid hydrogels (W–C gels), composed of PDMAEMA, cellulose nanowhisker (CNW) and carboxymethyl chitosan (CMCS), were prepared for developing a stimuli-responsive drug-release system. Compared to the neat gels, W–C gels exhibit improved properties, which are directly dependent on the content of both the CNW and CMCS. For W–C gels, an increase in the CNW has an obvious reinforcement effect, which could be strengthened further by an increased CMCS content, due to the strong interaction between these components. Better compression resistance and elasticity is also observed as the CNW and CMCS content increases. Moreover, the W–C gels retain good swelling capacity with obvious responsiveness to both pH and temperature, which is similar to that of neat gels; the ionization of CMCS increases the swelling ratio of gels in both acidic and alkaline conditions, except in a certain pH region (pH = 4–6), corresponding to the correlative isoelectric points (IEP) of CMCS with PDMAEMA, where a low swelling ratio is found. In the meantime, the increased CNW content brings about a decreased swelling ratio and a faster deswelling rate in the gels. To test the potential of W–C gels as drug carriers, flutamide was used as a target drug to analyze the drug-loading and release properties of the gels. The hybrid gels exhibit better drug-loading ability than neat gels; for W–C gels, a burst release is followed by a slow and sustained release, and the release of the drug could be controlled by deprotonation or protonation of PDMAEMA and CMCS in the gels under different pH conditions; this is fast in alkaline conditions and slow in acidic conditions, and the drug-release mechanism with a changed pH value could be explained by the superposition of Fickian diffusion.

Preparation and Characteristic of PC/PLA/TPU Blends by Reactive Extrusion

To overcome the poor toughness of PC/PLA blends due to the intrinsic properties of materials and poor compatibility, thermoplastic urethane (TPU) was added to PC/PLA blends as a toughener; meantime, catalyst di-n-butyltin oxide (DBTO) was also added for catalyzing transesterification of components in order to modify the compatibility of blends. The mechanical, thermal, and rheological properties of blends were investigated systematically. The results showed that the addition of TPU improves the toughness of PC/PLA blends significantly, with the increase of TPU, the elongation at break increases considerably, and the impact strength increases firstly and then falls, while the tensile strength decreases significantly and the blends exhibit a typical plastic fracture behavior. Meantime, TPU is conducive to the crystallinity of PLA in blends which is inhibited seriously by PC and damages the thermal stability of blends slightly. Moreover, the increased TPU makes the apparent viscosity of blends melt decrease due to the well melt fluidity of TPU; the melt is closer to the pseudoplasticity melt. Remarkably, the transesterification between the components improves the compatibility of blends significantly, and more uniform structure results in a higher crystallinity and better mechanical properties.

Robust and stimuli-responsive POSS hybrid PDMAEMA hydrogels for controlled drug release.

A new polyhedral oligomeric silsesquioxane (POSS) hybrid hydrogels were desinged and fabricated by introducing cationic octa-ammonium (Oa)-POSS) into chemically cross-linked cationic PDMAEMA hydrogels via in situ radical freezing polymerization. The prepared gels (shorten as OP-PD gels) show considerably improved properties through the effective incorporation and dispersion of Oa-POSS particles in gels. Comparing to the Oa-POSS-free gels, the hybrid gels own better mechanical properties with higher tensile and compressive strength. Meantime, except the decreased swelling ratio in acid condition, the OP-PD gels still keep excellent swelling ability with obvious pH and temperature double responsiveness, which is affected by the content of Oa-POSS slightly. All OP-PD gels exhibit an ultrarapid deswelling rate due to the interconnected micropores structure caused by freezing and the formation of microhydrophobic region around POSS particles. Moreover, the application potential of OP-PD gels in drug release was exploited by using flutamide as target drug, the result showed that the increased Oa-POSS could improve the drug loading ability, and OP-PD gels showed well controlled-release effect in simulated human stomachic condition.