Volume 44 Issue 9, September 2012

Recent developments in artificial cutters for site-selective scission of single-stranded DNA are described. With the cutters composed of two oligonucleotide additives and Ce(IV)/EDTA, long single-stranded DNA can be selectively cut at target site and manipulated according to our needs.

Interfacial entanglement and co-crystallization are identified to cause adhesion. Adhesion between polyethylene and different types of polypropylenes (PPs), including impact-modified PP isotactic PP and ethylene-propylene random copolymers, was increased with concentration of ethylene or ethylene–propylene rubber and faster cooling in co-extrusion. A more miscible interface is the key for improved adhesion.

Supramolecular films consisting of guanosine derivatives modified with a tetrathiafulvalene moiety have been prepared. The hydrogen bonding network of the guanosine unit enables the formation of a robust and self-supporting cast film by a solution process. The self-supporting films were mechanically flexible. The physical properties of the films of the derivatives depended on both the length of the alkyl chains and the structure of their terminal group. The composite film of the derivatives with 7,7,8,8,-tetracyanoquinodimethane exhibited electrical conductivity.

Un-expected large increase in crystallization temperature (c.a. 53 °C) was found for Nylon-6 nanocomposites with both kind of carbon nanotubes (CNTs) and plasma-polymerized CNTs (CNTM) compared with Nylon-6 homopolymer. This behavior was associated with a high level of dispersion of CNT in all nanocomposites and the ability of CNT to act like a nucleating agent for semi-crystalline polymers. Besides, the steps involved in polymerization procedure help in dispersion of CNT, which is reported for the first time.

Novel phenylethynyl (4-phenylethynyl phthalic anhydride) terminated addition-type imide oligomers derived from pyromellitic dianhydride and 2-phenyl-4,4′-diaminodiphenyl ether showed a high solubility and a very low minimum melt viscosity. These imide oligomers were also converted to crosslinked cured resins with Kapton-type backbone structures after curing at 370 °C. The glass transition temperature and elongation-at-break of the cured resins were extremely high (almost 350 °C and >10%, respectively). These epoch-making imide oligomers were found to have excellent processability for molding of fiber-reinforced plastics with high heat resistance.

Our approach concerning a photo-based patterning for general purpose polymer films is described. Patterned UV light irradiation of a thin polystyrene film under controlled temperature generates surface relief structures by mass transfer from shaded to irradiated areas. The resulting surface relief structure can be arbitrarily erased by heating and reconstructed by patterned ultraviolet (UV) light irradiation, and this process is repeatable. This new method thus enables fabrication of dynamic reversible patterning structures from various general polymers.

In order to study the kinetic mechanism of photochlorination of polyethylene, a proposed model was suggested in which the conversion of methylene (—CH₂—) units to chloromethylene (—CHCl—) ones were considered as the main reaction. The simplified versions of the obtained kinetic model indicate that the reaction is first order with respect to the chlorine gas concentration and zero order with respect to the methylene groups concentration up to 40% of chlorination, where the concentration of γ-methylene sequences is high. The mechanism of reaction was exactly reversed at higher conversions.

A novel Se-containing heterocycle 4,6-Bis(4′-hexylthiophen-2′-yl)thieno[3,4-c][1,2,5]selenadiazole (DTTSe) was synthesized for the first time and used as a new acceptor unit for developing donor−acceptor-conjugated copolymers.

In this study, we developed a method to prepare (R)-3-hydroxybutyryl-CoA for enzymatic cell-free polymerization, using crotonic anhydride as a starting material.