Both thermoresponsive flat membranes and core-shell microcapsule membranes, with (N-isopropylacrylamide) (PNIPAM) a porous membrane substrate and grafted poly N-isopropylacrylamide PNIPAM gates, were successfully prepared using a plasma-graft pore-filling polymerization method. PNIPAM was prepared to be grafted homogeneously onto the porous membrane sub-strates, in the direction of both the membrane thickness and surface. Regardless of the solute molecular size, temperature had an opposite effection diffusion coefficients of the solute across the PNIPAM-grafted membranes with low graft yields as opposed to those with high graft yields. The PE-g-PNIPAM membranes change from positive thermo-response to negative thermoresponse types with increasing pore-filling ratios at around 30%. Phenomenological models were developed for predicting the diffusion coefficient of the solute across PNIPAM-grafted membranes at temperatures, both above and be-low the lower critical solution temperature LCST. Predicted diffusional coefficients of solutes across both the PNIPAM-grafted flat and PNIPAM-grafted microcapsule membranes fit the experimental values. To obtain an ideal result for the diffusional thermoresponsive controlled release through PNIPAM-grafted membranes, the substrates strong enough to prevent any conformation changes are more suitable for preparing thermoresponsive membranes than weak ones.

Wehave successfully prepared monodispersed thermoresponsive core-shell hydrogel microspheres with a mean diameter of 200-400nm with poly (N-isopropylacrylamide-co-styrene) [P (NIPAM-co-St)] cores and poly (N-isopropylacrylamide) (PNIPAM) shells. The submicrometer-sized monodispersed P (NIPAM-co-St) core seeds were prepared by using a surfactant-free emulsion polymerization method, and the PNIPAM shell layers were fabricated onto the core seeds by using a seed polymerization method. The particle size, morphology and monodispersity, and thermoresponsive characteristics of the prepared microspheres were experimentally studied. In the preparation of P (NIPAM-co-St) seeds, with increasing the initiator dosage, the mean diameters and the dispersal coefficients were almost at the same levels at first; however, when the initiator dosage increased further to a critical amount, the mean diameters decreased drastically and the monodispersity became worse significantly. With increasing the stirring rate, the particle diameter decreased, and when the stirring rate was larger than 600 rpm, the monodispersity became worse obviously. With increasing the phase ratio, the mean diameter became larger simply, and the monodispersity became worse first and then became better again. With increasing the reaction time, the particle sizes nearly did not change, while the monodispersity gradually became better slightly. For the core-shell microspheres, with increasing the NIPAM dosage in the preparation of the PNIPAM shell layers, the mean diameters became larger simply, the monodispersity became better, and the thermoresponsive swelling ratio of the hydrodynamic diameters increased.

A glucose-sensitive microcapsule with a porous membrane and with linear-grafted polyacrylic acid (PAAC) chains and covalently bound glucose oxidase (GOD) enzymes in the membrane pores acting as functional gates was successfully prepared. Polyamide microcapsules with a porous membrane were prepared by interfacial polymerization, PAAC chains were grafted into the pores of the microcapsule membrane by plasma-graft pore-filling polymerization, and GOD enzymes were immobilized onto the PAAC-grafted microcapsules by a carbodiimide method. The release rates of model drug solutes from the fabricated microcapsules were significantly sensitive to the existence of glucose in the environmental solution. In solution, the release rate of either sodium chloride or VB12 molecules from the microcapsules was low but increased dramatically in the presence of 0.2mol/L glucose. The prepared PAAC-grafted and GOD-immobilized microcapsules showed a reversible glucose-sensitive release characteristic. The proposed microcapsules provide a new mode for injection-type self-regulated drug delivery systems having the capability of adapting the release rate of drugs such as insulin in response to changes in glucose concentration, which is highly attractive for diabetes therapy.

Wehave successfully prepared monodispersed thermoresponsive core-shell microcapsules with a mean diameter of about 4μm with a porous membrane and with linear-grafted poly (N-isopropylacrylamide) (PNIPAM) chains in the membrane pores acting as thermoresponsive gates. The preparation was carried out by using a Shirasu porous glass (SPG) membrane emulsification technique to prepare small-sized monodispersed oil-in-water emulsions and using interfacial polymerization to prepare the core-shell microcapsules with porous membranes. Plasma-graft pore-filling polymerization was used to graft linear PNIPAM chains into the pores of the microcapsule membranes. In the SPG membrane emulsification process, theoptimumsurfactant sodium dodecyl sulfate (SDS) concentrationandpoly (vinyl alcohol) stabilizer concentration could be selected by solely considering the monodispersity of the emulsion droplets. However, before the interfacial polymerization process was started, these two oncentrations needed to be monitored to avoid any aggregation of the microcapsules and, if necessary, the appropriate quantity of SDS or Tween 80 needed to be added to prevent the microcapsules from aggregating in the interfacial polymerization stage. The prepared PNIPAM-grafted monodispersed microcapsules with a mean diameter of about 4μm showed satisfactory reversible and reproducible thermoresponsive release characteristics. The release of both NaCl and vitamin B12 (VB12) from the PNIPAM-grafted microcapsules was slow at 25℃ and fast at 40℃, which is due to the closed/open state of the grafted "gates". The "on/off" ratio of the release rate of VB12 from the PNIPAM-grafted microcapsules was much larger than that of NaCl.

A thermo-responsive core-shell microcapsule with a porous membrane and poly (N-isopropylacrylamide) (PNIPAM) gates was prepared using interfacial polymerization to prepare polyamide core-shell microcapsules, and plasma-graft pore-filling polymerization to graft PNIPAMinto the pores in the microcapsule wall. The proposed thermo-responsive microcapsule could be a positive thermo-response controlled-release one or a negative thermo-response one by changing the PNIPAM graft yield. When the graft yield is low, the release rate from the microcapsules is higher at temperatures above the lower critical solution temperature (LCST) than that below the LCST, due to the opened/closed pores in the microcapsule membranes controlled by the PNIPAM gates. In contrast, when the graft yield is high, the release rate is lower at temperatures above the LCST than that below the LCST, due to the hydrophilic/hydrophobic phase transition of the PNIPAM gates.