Benzyne as a Monomer for Polymerization:  Alternating Copolymerization of Benzyne and Pyridine To Give Novel Polymers witho-Phenylene and 2,3-Dihydropyridine Units in the Main Chain

2005 ◽  
Vol 38 (6) ◽  
pp. 2167-2172 ◽  
Author(s):  
Eiji Ihara ◽  
Atsushi Kurokawa ◽  
Takeshi Koda ◽  
Takahito Muraki ◽  
Tomomichi Itoh ◽  
...  
Keyword(s):  
Main Chain ◽  
Alternating Copolymerization

scholarly journals Asymmetric catalytic synthesis of polyketones and polycarbonates

2004 ◽  
Vol 76 (3) ◽  
pp. 541-546 ◽  
Author(s):  
K. Nozaki
Keyword(s):  
Main Chain ◽  
Active Species ◽  
Nitrile Group ◽  
Optically Active ◽  
Side Chain ◽  
Optically Active Polymers ◽  
Theoretical Studies ◽  
Cyclohexene Oxide ◽  
Asymmetric Catalytic ◽  
Alternating Copolymerization

Two examples are presented for the synthesis of optically active polymers with main-chain chirality from achiral monomers using chiral metal-complexes as catalysts. Asymmetric alternating copolymerization of α-olefins with carbon monoxide provided optically active polyketones when catalyzed by an (R,S)-BINAPHOS-Pd complex. From propene and CO, highly isotactic polyketone with high enantioselectivity (>97 % like diad and >95 % ee). Spectroscopic and theoretical studies revealed that the olefin insertion is the key step for the enantiofacial selection and that this step takes place at cis to the phosphine part of (R,S)-BINAPHOS. The catalyst is applicable not only to propene/CO but also to styrene/CO, which enabled the first asymmetric terpolymerization of propene/styrene/CO. The catalyst tolerates funational groups such as fluorocarbons and a nitrile group so that they can be incorporated in the side chain. Optically active polycarbonate was also synthesized by the alternating copolymerization of cyclohexene oxide with carbon dioxide via the desymmetrization of the meso-epoxide. Dinuclei zinc species prepared from diethylzinc, ethanol, and α,α'-diphenylprolinol, was revealed to be the real active species.

Temperature-dependent photoluminescence from MEH-PPV and MEH-OPPV containing oxadiazole in the main chain

2006 ◽  
Vol 84 (1-2) ◽  
pp. 203-206 ◽  
Author(s):  
F. Kong ◽  
X.L. Wu ◽  
G.S. Huang ◽  
R.K. Yuan ◽  
C.Z. Yang ◽  
...  
Keyword(s):  
Main Chain ◽  
Temperature Dependent ◽  
Temperature Dependent Photoluminescence

scholarly journals Internal constraints and arrested relaxation in main-chain nematic elastomers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Takuya Ohzono ◽  
Kaoru Katoh ◽  
Hiroyuki Minamikawa ◽  
Mohand O. Saed ◽  
Eugene M. Terentjev
Keyword(s):  
Mechanical Properties ◽  
Main Chain ◽  
Polymer Networks ◽  
Nematic Order ◽  
Nematic Elastomers ◽  
Nematic Director ◽  
Highly Nonlinear ◽  
Nonlinear Mechanical ◽  
Liquid Crystal Elastomers ◽  
Memory Applications

AbstractNematic liquid crystal elastomers (N-LCE) exhibit intriguing mechanical properties, such as reversible actuation and soft elasticity, which manifests as a wide plateau of low nearly-constant stress upon stretching. N-LCE also have a characteristically slow stress relaxation, which sometimes prevents their shape recovery. To understand how the inherent nematic order retards and arrests the equilibration, here we examine hysteretic stress-strain characteristics in a series of specifically designed main-chain N-LCE, investigating both macroscopic mechanical properties and the microscopic nematic director distribution under applied strains. The hysteretic features are attributed to the dynamics of thermodynamically unfavoured hairpins, the sharp folds on anisotropic polymer strands, the creation and transition of which are restricted by the nematic order. These findings provide a new avenue for tuning the hysteretic nature of N-LCE at both macro- and microscopic levels via different designs of polymer networks, toward materials with highly nonlinear mechanical properties and shape-memory applications.

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