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Cross-linked poly(methyl methacrylate) (PMMA) microspheres have been successfully prepared by using the asymmetric cross-linker allyl methacrylate (AMA) via dispersion polymerization. The influence of the AMA amount and polymerization process on the PMMA particle size and morphology has been studied thoroughly. It was found that micron-sized, cross-linked PMMA particles with narrow size distributions could be obtained by a semi-continuous process with the asymmetric cross-linker AMA. The obtained micron-sized, cross-linked PMMA particles could be further used as a light diffusion agent in a polycarbonate matrix, and their light diffusion properties were significantly enhanced by increasing the gel content in the cross-linked particles. Moreover, the influence of the polymerization process, cross-linker content in PMMA and PMMA content in the polycarbonate matrix on light diffusion was carefully investigated. The results showed that the PMMA particles containing 5.0 wt% AMA, obtained by semi-continuous polymerization, had a higher haze and gel content and exhibited a better light diffusion effect than did the other particles. [ABSTRACT FROM AUTHOR]

Nanoscale poly(alkyl methacrylate)s including poly(methyl methacrylate), poly(ethyl methacrylate), poly(cyclohexyl methacrylate), poly(iso-butyl methacrylate) and poly(benzyl methacrylate) were prepared by a modified microemulsion polymerization procedure. NMR analysis suggested that these poly(methacrylate)s samples were higher in syndiotactic content, lower in isotactic content and the glass transition temperatures (Tgs) of them were also higher than those reported in the literature. The tacticities of the poly(methacrylate)s, beside the restricted volume effect of nanoparticles during the modified microemulsion polymerization, were mainly influenced by the reaction temperature, the lower the reaction temperature, the higher the syndiotacticity of the products. The syndiotacticity of the product decreased obviously when the polymerization was carried out at a temperature far above the Tg of the resulting polymer. It was also shown that the tacticity of the polymer was affected by the monomer structure, a monomer with the bulkier alkyl side group would liable to result in a polymer with richer syndiotacticity. Possible mechanism of rich-syndiotacticity was also discussed. [ABSTRACT FROM AUTHOR]

Nanoscale poly(cyclohexyl methacrylate) (PCHMA) particles were prepared by a modified microemulsion polymerization procedure. 13C-NMR analysis suggested that such PCHMA samples were higher in syndiotactic content (61-72% rr) and lower in isotactic content (1-3% mm). The glass transition temperatures (Tg's) of the products were also higher than that reported in the literature. The polymer properties, such as particle size, molecular weight, tacticity, and Tg were affected by the reaction conditions. The smaller the particle size, the higher the syndiotacticity, the lower the isotacticity and the greater the molecular weight, then the higher the Tg of the PCHMA samples. Possible mechanism of rich-syndiotacticity was also discussed. [ABSTRACT FROM AUTHOR]

Modified microemulsion polymerization is a useful method to prepare nanoscale poly(methyl methacrylate) (PMMA) latex with a high solid content (10–30 wt%) and nanoscale (20–40 nm) particles by only using 1–2 wt% surfactant. The main feature of modified microemulsion polymerization is that most of the monomer is post‐added gradually into the initiated pre‐microemulsion, and the surfactant can be utilized adequately. We find that the polymerization rate increases with the increasing of the post‐addition rates, using the Mettler Toledo Reaction Calorimeter to accurately record the heat of reactions and calculate data. Furthermore, after analyzing the products in GPC, the post‐addition rate is found to significantly influence the molecular weight of polymer: the molecular weight also increases with the increasing of the post‐addition rate. [ABSTRACT FROM AUTHOR]

Semi-transparent reactive microgel in nanosize has been prepared by modified microemulsion polymerization using a common emulsifier, crosslinking agent and functional monomer. The microgels are translucent reactive nanoparticles, with the size of 40–100 nm, consisting of inner-crosslinked polymer up to 40%. FT-IR proved the functional groups, such as epoxy and hydroxy, are on the surface of the microgel nanoparticles. Rheological detection demonstrated the apparent pseudoplasticity of the non-aqueous microgel dispersion prepared by the phase transfering from the O/W microlatexes. [ABSTRACT FROM AUTHOR]

Abstract: Monte Carlo simulation of chemically reacting systems based on the master equation was used to describe the stochastic time evolution of the microemulsion polymerization system. A model was developed to demonstrate its applicability for hexyl methacrylate and styrene microemulsion polymerization. The properties of final latex, such as the particle size and molecular weight distributions were obtained simultaneously. The polymerization behavior and properties of final latexes were well reproduced. The model is valuable in confirming or elucidating the various mechanisms in the polymerization. The entry and desorption mechanism was well established to account for the polymerization kinetics. The general polymerization behavior of hydrophobic monomer in microemulsions was properly simulated by the model proposed. [Copyright &y& Elsevier]

Nanoscale poly(ethyl methacrylate) (PEMA) particles were prepared by a monomer post-added microemulsion polymerization procedure. ¹H NMR analysis suggested that the PEMA samples were rich in syndiotactic content (58-64% rr) and lower in isotactic content (4-6%mm). The glass transition temperatures (Tg's) of the products were also higher than those of the PEMA samples prepared by ordinary free-radical polymerization. The polymer properties, such as particle size, molecular weight, tacticity, and Tg were affected by the reaction conditions. The smaller the particle size, the higher the syndiotacticity, the lower the isotacticity, the greater the molecular weight, then the higher the Tg of PEMA. A possible mechanism of rich-syndiotacticity was also discussed primarily. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, novel thermosensitive poly(N-isopropylacrylamide) (PNIPAM) nanocapsules with temperature-tunable diameter and permeability are reported. Firstly, the core-shell composite microparticles were synthesized by precipitation polymerization with isothiocyanate fluorescein (FITC) entrapped SiO2 as core and cross-linked PNIPAM as shell. Then, the SiO2 core was etched by hydrofluoric acid at certain condition and the pre-trapped FITC molecules remained within the inner cavity. The FITC release profile and TEM studies clearly indicate that the release behavior of FITC could be controlled effectively by the external temperature. Above the LCST of PNIPAM (32°C), the dehydrated PNIPAM shell inhibited the release of FITC from the internal cavity while below its LCST, the fluorophore could permeate the swollen shell easily. [Copyright &y& Elsevier]

Copolymer microspheres consisting of styrene and N-vinyl carbazole (NVC) have been prepared by dispersion polymerization. The effects of various polymerization parameters on the particle size were systematically studied. The particle size increased with the decrease of the system's initial solubility parameter and stabilizer concentration. When a small amount of inhibitor was added into the system, the particle size notably increased and the particle size distribution widened. The ratio of styrene to NVC in the monomer mixture had no obvious effect on particle size. The amount of NVC in the copolymers increases with the increase of NVC in the monomers. [ABSTRACT FROM AUTHOR]

A strategy is presented to control the disassembly of nanogels using near‐infrared light. Novel diselenide‐cross‐linked nanogels with a newly synthesized diselenide cross‐linker are prepared. Indocyanine green is incorporated into nanogels to trigger the cleavage of diselenide bond through generating reactive oxygen species. The appropriate control of illumination allows for on‐demand degradation of nanogels and controlled drug release. [ABSTRACT FROM AUTHOR]

Abstract: pH-responsive polymer shell chitosan/poly (methacrylic acid) (CS-PMAA) was coated on mesoporous silica nanoparticles (MSN) through the facile in situ polymerization method. The resultant composite microspheres showed a flexible control over shell thickness, surface charges and hydrodynamic size by adjusting the feeding amount of MSN and the molar ratio of [–NH2]/MAA. The MSN/CS-PMAA composite microspheres were stable in the pH range of 5–8 as well as in the physiological saline (0.15M NaCl). Doxorubicin hydrochloride (DOX) was applied as a model drug to investigate the drug storage and release behavior. The results demonstrated that DOX could be effectively loaded into the composite microspheres. The cumulative release of DOX-loaded composite microspheres was pH dependent and the release rate was much faster at low pH (5.5) than that of pH 7.4. The cytotoxicity test by MTT assay showed that the blank carrier MSN/CS-PMAA microspheres were suitable as drug carriers. The cellular uptake of composite microspheres was investigated by confocal laser scanning microscopy (CLSM), which indicated that MSN/CS-PMAA could deliver the drugs into HeLa cell. The above results imply that the composite microspheres are a promising drug delivery system for cancer therapy. [Copyright &y& Elsevier]

Abstract: Raspberry-like magnetic polystyrene microspheres were prepared via soap-free emulsion polymerization using 2,2′-azobis(2-methylpropionamidine) dihydrochloride (V50) as initiator. The effect of polymerization parameters, such as initiator type, initiator content and the feeding sequence on the particle size and morphology of magnetic polystyrene microspheres, were examined. The final magnetic polystyrene microspheres were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). The experimental results showed that V50 was a suitable initiator for preparation of raspberry-like magnetic polystyrene microspheres. [Copyright &y& Elsevier]