Practical Preparation of 2‐Halomethyl‐Allyl Carboxylates

An improved, efficient preparation of 2‐(halomethyl)allyl carboxylates starting from diethyl bis(hydroxymethyl)malonate and hydrobromic acid is reported. The allylic halogen of 2‐(chloromethyl)acrylate and 2‐(bromomethyl)acrylate are readily exchanged during esterification.     

Radiation-Induced Polymerization of Acrylic Esters at High Pressure and Pressure-Volume Behavior of Polymer-Monomer Coexistence System as Polymerized

Pressure-volume (P-V) behavior and radiation-induced polymerization of methyl and n-butyl acrylic esters (MA and BA, respectively) were studied up to 7000 kg/cm² at 20°C. The P-V isotherms broke at 1900 and 1200 kg/cm² for MA and BA, respectively. The P-V isotherm for MA was not smooth in the pressure range between 3500 and 4000 kg/cm². The polymerization behavior varied with change in the P-V behavior; the polymerization rates were maximum at 1800 kg/cm for MA and 1000 kg/cm² for BA, and then minimum at 1900 kg/cm² for MA and 1100 kg/cm² for BA. The polymerization rates increased again above the pressures giving the minimum rates up to about 3000 kg/cm². Above 3000 kg/cm² the pressure dependence of the rates decreased up to 4000 and 4500 kg/cm² for MA and BA, respectively. Above these pressures, the pressure dependence of polymerization rates increased again. The P-V isotherms of as-polymerized polymer-monomer coexistence systems showed characteristic behavior near the polymerization pressure. From a comparison of these polymerizations and P-V behavior with those of methacrylic esters, we propose that acrylic esters align at high pressure and that freedom of rotation of ester group plays an important role in the mode of pressure-induced alignment of monomer molecules.     

Preparation of thermosensitive polymeric organogels and their drug release behaviors

Stimuli-sensitive drug delivery systems—in particular, stimuli-sensitive polymeric hydrogels swollen with water—have attracted considerable attention in medical and pharmaceutical fields. This study concerns with the synthesis of thermosensitive polymeric organogels for controlled drug release; a copolymerization of stearyl acrylate (SA) with a cross-linker and the loading of indomethacin as a model lipophilic drug were accomplished in oleyl alcohol. The pulsatile (on-off) drug release was successfully conducted: release was halted at 36 °C and release occurred at over ca. 40 °C. This drug release pattern is suitable for thermochemotherapy combined with hyperthermia. The differential scanning calorimetric measurement suggests the following mechanism: the ordered crystalline structure, i.e., the alignment of hydrophobic alkyl side chains, works to prevent indomethacin diffusion from the organogel below the crystallization temperature, while the disordered amorphous structure above the melting temperature allows indomethacin to diffuse.     

Modification and chemical transformation of Si(1 1 1) surface

Modification of hydrogen-terminated Si(1 1 1) surfaces by hydrosilylation of activated alkenes and further chemical transformation of the modified surfaces is reported. A Si(1 1 1)-H surface was reacted with activated alkenes such as acrylate esters, acrylonitrile, and maleic anhydride under mild conditions to give modified surfaces with terminal functional groups. A modified surface with a terminal ester group was reduced by LiAlH₄ to give a hydroxy-terminated surface, and the hydroxy-terminated surface was transformed to a bromo-terminated surface. XPS analysis revealed that the brominated surface (Si(1 1 1)-CH₂CH₂CH₂Br) had 32% coverage with the 3-bromopropyl group. Ester and amide formation reactions were carried out on hydroxy- and carboxy-terminated Si surfaces by reaction with tert-butoxycarbonyl glycine, glycine tert-butyl ester, 2,2,2-trifluoroethanol and 4-trifluoromethylbenzyl alcohol in the presence of carbodiimide. XPS characterization indicated that the esters and amide were successfully formed with coverage ranging from 16% to 58%. Coverage ratios of octadecyl ester modified surfaces were also estimated by combination of surface reduction and gas chromatography analysis to be 25-35%.     

UV-curable coatings of highly crosslinked trimethylmelamine based acrylates and methacrylates

The synthesis and characterization of N¹,N²,N³-trimethylmelamine based (meth)acrylates and their application as components of UV-curable lacquers is described. A pre-condensed oligomeric mixture with a degree of condensation up to five is obtained via a one-pot conversion. Dividing the synthesis into two steps gives access to the mostly monomeric tris(meth)acrylates in overall yields higher than 76%. In general, the prepared compounds can easily be applied on glass, metal, and polystyrene glass affording highly transparent, hard, and scratch resistant coatings after UV-curing. The UV-cured monomeric trimethylmelamine trisacrylate was fully characterized by means of hardness, gloss, scratch-, abrasion-, and chemical resistance. Remarkably, the trimethylmelamine trisacrylate does not release cancerogen formaldehyde even at 150 °C.     

MOLECULAR INTERACTIONS OF CARBOXYLATED URETHANE ACRYLATE IONOMERS IN LOW-POLARITY AND POLAR SOLVENTS

Carboxylated urethane acrylate ionomers that have a small number of ionic groups per chain were synthesized with varying the molecular weight of soft segment, the degree of ionization, and the sort of diisocyanate. The effect of intra-and intermolecular interactions on solution properties was studied by viscosity measurements in low-polarity and polar solvents. In a low-polarity solvent (1,4-dioxane), ionomers showed almost no intramolecular interaction at dilute concentration and a small degree of intermolecular interaction at high concentrations, resulting from a small number of ionic groups per chain. In a polar solvent (dimethylacetamide, DMAc), ionomers showed typical polyelectrolyte behavior, even though ionomers have a small number of ionic groups per chain. Intermolecular interaction caused by polyether soft segment, phenyl group, and hydrogen bond between urethane acrylate ionomer chains contributed to the increase of reduced viscosity at low concentration.     

Synthesis and Enzymatic Degradation of Aliphatic Polyesters Copolymerized with Trimesic Acid

Abstract

Network copolyesters were made from adipic acid and ethylene glycol with 10–40 mol% trimesic acid (Y). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and postpolymerized at 260°C for various times to form a network. The degree of reaction (D _R), estimated from the infrared absorbance of hydroxyl and methylene groups, increased with increasing postpolymerization time and leveled out at about 90% after 4–6 hours. Heat distortion temperatures (T _h) measured by thermomechanical analysis increased greatly from ?83 to 48°C upon the incorporation of Y. Wide-angle x-ray diffraction patterns showed that the copolymer films are amorphous. Density, tensile strength, and Young's modulus decreased for the copolymers with 10–30 mol% Y, whereas they increased drastically for the copolymer with 40 mol% Y. The enzymatic degradation was estimated by the weight loss of the copolymer films in buffer solutions with a lipase at 37°C. The weight loss decreased remarkably with increasing Y and showed no weight loss for the copolymer with 40 mol% Y. On the other hand, the weight loss by alkali hydrolysis increased for the copolymers with 10 and 20 mol% Y, implying a difference in the degradation mechanism between enzymatic degradation and alkali hydrolysis.     

Monitoring frontal photopolymerization by electroresistance

The frontal photopolymerization of acrylates was conducted in tube with TPO as bleachable photoinitiator and was identified to reach complete conversion in the formed polymer phase. The spatiotemporal temperature profiles of the frontal photopolymerization of acrylates were detected with a series of immobilized thermocouples along with the reactor. Monomer with high functionality resulted great summit temperature and was favorable for accelerating the traveling of polymerization front. It was found that the front traveling may be affected by the protruded thermocouples head. Based on the sudden increase of electrical resistance during rapid photopolymerization, an electrical measurement was setup to follow the front traveling of frontal photopolymerization.     

Effect of C-Tetramethyl Calix[4]resorcinarene Acrylate on Curing Behavior and Film Properties of Thiol-acrylate Coating System

An octa-functional acrylate of C-tetramethyl calix[4]resorcinarene(CMC-4-RA) was facilely synthesized and characterized with 1H NMR, 13C NMR and FTIR spectroscopy. The CMC-4-RA was added to a thiol-acrylate system with different mass ratios, and exposed to a middle pressure mercury lamp. The maximum photopolymerization rate and final vinyl group conversion in the cured film increased greatly along with CMC-4-RA addition that was monitored with Photo-DSC. The tensile strength and pendulum hardness were impro...     

聚硫橡胶和环氧树脂互穿网络和共聚网络

本文以丙烯酸酯封端的聚硫橡胶，环氧封端的聚硫橡胶分别同双酚环氧树脂合成互穿网络和共聚网络，并研究了它们的相结构和性能。结果表明，所有样品都具有低温柔性和良好的力学性。