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The deviant and irregular polymerization behavior of 4-acetoxystyrene was found through the detailed study on the ATRP of various para-substituted styrenes bearing electron-withdrawing and electron-donating groups. The relationship between the rate constant for polymerization rate and the Hammett parameter was discussed.
We described the synthesis of PGA via an azeotropic distillation method that enables tunable molecular weights. This alternative method produces a white powdered PGA rather than a waxy brown product that is obtained by conventional melt-solid condensation methods. Additionally, improved solubility renders this method useful for producing soluble high molecular weight PGA for further applications. Highly crystalline PGA with a high molecular weight (Mn = 32,100 g/mol) was obtained with a homogenous polydispersity index of 1.2–1.4.
We prepared ionic conductive compound (ICC) by solution casting and the in situ polymerization of poly(ethylene glycol) methyl ether methacrylate (OEGMA) in the presence of PMMA and a cross-linking agent. Then, ionic conductive polymer blends was obtained by melt-mixing ICC and poly(L-lactic acid) (PLLA). We studied the relationship between phase structure and physical properties such as electrical and mechanical properties of the blends.
The toughness and flame retardancy of glass fiber (GF)-reinforced polycarbonate (PC) composites were tested by adding four impact modifiers and three kinds of flame reardants. Silicon acrylate rubber (SiR) could significantly toughen the composites by 2.52 times. Then only by addition of 0.2 wt% oligomeric siloxane-containing potassium dodecyl diphenylsulfone sulfonate (SiKSS), PC/GF/SiR composites can achieve good flame retardancy with a V0 rating in UL-94 burning vertical test. This formulation also maintained the system a relative high heat deflection temperature around 120 °C.
The electro-optic properties of polymer-stabilized blue phases (PSBP) with polar chiral dopant and polar substituent on polymer were significantly enhanced, which is in sharp contrast with the trend observed for PSBP with conventional chiral dopant. These results indicate that polar chiral dopant showing good affinity with polar polymer induces weak anchoring condition inside PSBP.
A novel surface wrinkling system, based on the fabrication of a polyion complex (PIC) skin layer, is introduced. PIC skin layers are fabricated on the surface of chitosan (CS) films via immersion in sodium alginate (AG) solutions. After removal of excess adsorbed AG, microscopic wrinkles appear upon drying. Water resistance in the wrinkled films was achieved by thermal crosslinking of the PIC skin layer. The thermally crosslinked wrinkled surfaces that were composed of covalently crosslinked CS and AG exhibited low cell adhesiveness and are suitable for use in implantable materials.
We optimized the sonoporation of a suspension culture with microbubbles for labeling and MR tracking of mesenchymal stem cells (MSCs). When water was used as the transmission medium between the acoustic probe and cell suspension, microbubbles gently collapsed with minimal cell damage. Under this condition, the number of labeled MSCs was 25%, which is 3.3-fold greater than the number of MSCs labeled using the conventional electroporation system, and the cell viability was maintained at approximately 80%. The MRI signal could be clearly observed for 2.0 × 106 MSCs.
The effect of silica nanoparticle size and concentration on the mechanical strength and wellbore plugging performance of SPAM/ chromium (III) acetate nanocomposite gels was investigated. First, the rheological behavior of gelant, surface chemistry, morphology, and viscoelastic properties of synthesized nanocomposites were investigated. In addition, an experimental setup was designed to determine the maximum differential compressive pressure (DCP) that the synthesized nanocomposite gels can tolerate before failing. The nanocomposites containing 20–30 nm particles have a higher DCP in comparison to those having 7–10 and 60–70 nm nanoparticles.
