Controllable synthesis of nanosilica surface-grafted PMMA macromonomers via catalytic chain transfer polymerization

Preparation of Biocompatible Poly(2-(methacryloyloxy)ethyl phosphorylcholine) Hollow Particles Using Silica Particles as a Template

Hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) shows biocompatibility because the pendant phosphorylcholine group has the same chemical structure as the hydrophilic part of phospholipids that form cell membranes. Hollow particles can be used in various fields, such as a carrier in drug delivery systems because they can encapsulate hydrophilic drugs. In this study, vinyl group-decorated silica particles with a radius of 150 nm were covered with cross-linked PMPC based on the graft-through method. The radius of PMPC-coated silica particles increased compared to that of the original silica particles. The PMPC-coated silica particles were immersed in a hydrogen fluoride aqueous solution to remove template silica particles to prepare the hollow particles. The PMPC hollow particles were characterized by dynamic light scattering, infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy observations. The thickness of the hollow particle shell can be controlled by the polymerization solvent quality. When a poor solvent for PMPC was used for the polymerization, PMPC hollow particles with thick shells can be obtained. The PMPC hollow particles can encapsulate hydrophilic guest molecules by immersing the hollow particles in a high-concentration guest molecule solution. The biocompatible PMPC hollow particles can be used in a drug carrier.

PTFE/EP Reinforced MOF/SiO2 Composite as a Superior Mechanically Robust Superhydrophobic Agent towards Corrosion Protection, Self-Cleaning and Anti-Icing

Organic resin cross-linking ZIF-67/SiO₂ superhydrophobic (SHPB) multilayer coating was successfully fabricated on metal substrate. The perfluoro-octyl-triethoxy silane (POTS) modified ZIF-67 and SiO₂ coating was applied on primary coated polytetrafluoroethylene (PTFE) and epoxy resin (EP) via spray coating method. Here, we present that the robust superhydrophobicity can be realized by structuring surfaces at two different length scales, with a nanostructure design to provide water repellence and a microstructure design to provide durability. The as-fabricated multilayer coating displayed superior water-repellence (CA=167.4°), chemical robustness (pH=1-14) and mechanical durability undergoing 120th linear abrasion or 35th rotatory abrasion cycle. By applying different acidic and basic corrosive media and various weathering conditions, it can still maintain superior-hydrophobicity. To get a better insight of interaction between inhibitor molecules and metal surface, density functional theory (DFT) calculations were performed, showing lower energy gap and increased binding energy of ZPS/SiO₂ /PTFE/EP (ZPS=ZIF-67+POTS) multilayer coating compared to the ZIF-67/SiO₂ /PTFE/EP, thereby supporting the experimental findings. Additionally, such coatings may be useful for applications such as anti-corrosion, self-cleaning, and anti-icing multi-functionalities.

Study on morphology and mechanical properties of PMMA-based nanocomposites containing POSS molecules or functionalized SiO2 particles

Nanocomposites of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) and functionalized SiO2 were investigated in order to determine the effect of particles on the morphology and mechanical properties of PMMA. The outcome of the study suggested that functionalized SiO2 and octavinylPOSS molecule had different morphology. As proved by X-ray diffraction and transmission electron microscopy analysis, the crystal structure of OVPOSS molecule was significantly different from amorphous aggregates of functionalized SiO2. With the additional particles in the nanocomposites, the sizes of octavinylPOSS and functionalized SiO2 began to reduce. This illustrated that the separation of aggregates led to the formation of irregular POSS molecules and amorphous SiO2 particles varied. Differential scanning calorimetry analysis indicated that PMMA-POSS nanocomposites had a homogeneous system. However, there was a significant phase separation at 3 wt.% SiO2. PMMA-SiO2 nanocomposites displayed lower reinforcing effects than expected, based on the mechanical properties of nanocomposites containing OVPOSS molecules.

Controllable fabrication of nanocrystal-loaded photonic crystals with a polymerizable macromonomer via the CCTP technique

We report an alternative strategy for fabricating nanocrystal-loaded photonic crystals with a polymerizable macromonomer via catalytic chain-transfer polymerization (CCTP) in which CoBF acted as a chain-transfer agent (CTAs). First, monodisperse, functionalized PS-co-PMAA microspheres with polystyrene (PS) cores and poly(methacrylic acid) (PMAA) shells were controllably prepared using styrene and the as-prepared PMAA macromonomer by surfactant-free emulsion polymerization. Then Cd(0.4)Zn(0.6)S nanocrystals capped with as-prepared PMAA macromonomer were synthesized by an in situ growth method. Finally, Cd(0.4)Zn(0.6)S nanocrystal-loaded PS-co-PMAA microspheres hybrids were obtained through simply mixing an aqueous solution of PS-co-PMAA microspheres with an aqueous solution of Cd(0.4)Zn(0.6)S nanocrystals in the appropriate proportions; the multianchor -COOH groups on the surface of core-shell PS-co-PMAA microspheres favor incorporation with Cd(0.4)Zn(0.6)S nanocrystals. Scanning electron microscopy (SEM) images confirm that PS-co-PMAA microspheres are uniformly surrounded by Cd(0.4)Zn(0.6)S nanocrystals. In addition, discrete electronic and photonic states can be combined both with PS-co-PMAA photonic crystals and fluorescent semiconductor Cd(0.4)Zn(0.6)S nanocrystals.

Controllable synthesis of new polymerizable macrosurfactants via CCTP and RAFT techniques and investigation of their performance in emulsion polymerization

We reported herein the synthesis of poly(methacrylic acid)-b-poly(butyl acrylate) (PMAA-b-PBA) block copolymers (surfmers) and their performance as novel polymerizable macrosurfactants in emulsion polymerization. The surfmers bearing terminal unsaturated carbon-carbon double bonds were first successfully designed and sythesized via catalytic chain transfer polymerization (CCTP) and radical addition-fragmentation polymerization (RAFT) techniques. The structures of surfmers were characterized by Raman spectra, nuclear magnetic resonance ((1)H NMR), and gel permeation chromatography (GPC). The critical micelle concentration of surfmers was determined. Subsequently, the surfmers were used as emulsifier to prepare polyacrylate latexes (PA-surf). The influence of the surfmer concentration as well as PMAA and PBA chain segment ratios of surfmer on their performance in emulsion polymerization was discussed thoroughly. The particle size, amount of coagulum, and stability against electrolyte solutions of the latexes were evaluated. Also, the relations between monomer conversion in emulsion polymerization, polymerization rate, emulsion particle size, surface tension, and reaction time were investigated, which showed some interesting information for the probable mechanism underlying this emulsion polymerization system. Atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectra (ATR FT-IR) were performed to investigate the surface morphology and component distribution of the latex films. The results show high efficiency of these surfmers in emulsion polymerization, suggesting that the resultant PMAA-b-PBA block copolymers act not only as the emulsifier but also as the stabilizer of monomer droplets as well as the so-called comonomer.