scholarly journals Enantioselective terpolymerization of racemic andmeso-epoxides with anhydrides for preparation of chiral polyesters

2020 ◽  
Vol 117 (27) ◽  
pp. 15429-15436
Author(s):  
Jie Li ◽  
Ye Liu ◽  
Wei-Min Ren ◽  
Xiao-Bing Lu
Keyword(s):  
Crystallization Behavior ◽  
Random Distribution ◽  
Main Chain ◽  
Glycidyl Ether ◽  
Catalyst System ◽  
Optically Active ◽  
The Other ◽  
Cyclohexene Oxide ◽  
Convenient Route ◽  
Butyl Glycidyl Ether

The preparation of stereochemistry- and sequence-defined polymers, in which different monomer units are arranged in an ordered fashion just like biopolymers, is of great interest and has been a long-standing goal for chemists due to the expectation of unique macroscopic properties. Here, we describe the enantioselective terpolymerization of racemic terminal epoxides,meso-epoxides, and anhydrides mediated by the privileged chiral dinuclear Al(III) catalyst system, to afford optically active polyester terpolymers with either gradient or random distribution as determined by the epoxides employed during their preparation. The enantioselective terpolymerization of racemictert-butyl glycidyl ether (rac-TBGE) and cyclopentene oxide with phthalic anhydride (PA) or naphthyl anhydride (NA) gives novel gradient polyesters, in which the crystallization behavior varies continuously along the main chain, due to the decrement of one ester component and the increment of the other occurring sequentially from one chain end to the other. In contrast, the enantioselective terpolymerization ofrac-TBGE andmeso-epoxide (cyclohexene oxide, 3,4-epoxytetrahydrofuran, or 1,4-dihydronaphthalene oxide) with an anhydride (PA or NA) provided chiral statistical terpolyesters with the random distribution of two kinds of ester units, resulting in a material possessing a mixed glass transition temperature. The present study therefore provides a convenient route to chiral polyesters bearing a range of physical and degradability properties.

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.

scholarly journals Autonomously Replicating Macronuclear DNA Pieces Are the Physical Basis of Genetic Coassortment Groups in Tetrahymena thermophila

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1119-1125
Author(s):  
Laura Wong ◽  
Lana Klionsky ◽  
Steve Wickert ◽  
Virginia Merriam ◽  
Eduardo Orias ◽  
...  
Keyword(s):  
Random Distribution ◽  
Tetrahymena Thermophila ◽  
Physical Basis ◽  
The Other ◽  
Site Specific ◽  
Phenotypic Assortment ◽  
Somatic Genome

Abstract The macronucleus of the ciliate Tetrahymena thermophila contains a fragmented somatic genome consisting of several hundred identifiable chromosome pieces. These pieces are generated by site-specific fragmentation of the germline chromosomes and most of them are represented at an average of 45 copies per macronucleus. In the course of successive divisions of an initially heterozygous macronucleus, the random distribution of alleles of loci carried on these copies eventually generates macronuclei that are pure for one allele or the other. This phenomenon is called phenotypic assortment. We have previously reported the existence of loci that assort together (coassort) and hypothesized that these loci reside on the same macronuclear piece. The work reported here provides new, rigorous genetic support for the hypothesis that macronuclear autonomously replicating chromosome pieces are the physical basis of coassortment groups. Thus, coassortment allows the mapping of the somatic genome by purely genetic means. The data also strongly suggest that the random distribution of alleles in the Tetrahymena macronucleus is due to the random distribution of the MAC chromosome pieces that carry them.

scholarly journals Hydrophobization of arabinoxylan with n-butyl glycidyl ether yields stretchable thermoplastic materials

2021 ◽  
Author(s):  
Parveen Kumar Deralia ◽  
Aline Maire du Poset ◽  
Anja Lund ◽  
Anette Larsson ◽  
Anna Ström ◽  
...  
Keyword(s):  
Glycidyl Ether ◽  
Butyl Glycidyl Ether

Conjugated Polymers with Main Chain Chirality. 3. Synthesis of Optically Active Poly(aryleneethynylene)s

1996 ◽  
Vol 29 (15) ◽  
pp. 5083-5090 ◽  
Author(s):  
Liang Ma ◽  
Qiao-Sheng Hu ◽  
Kwon Yon Musick ◽  
Dilrukshi Vitharana ◽  
Chi Wu ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Main Chain ◽  
Optically Active

Poly(amide) oligomers with silarylene and/or germarylene units – synthesis, characterization and thermal studies

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Luis H. Tagle ◽  
Claudio A. Terraza ◽  
Angel Leiva ◽  
Patricia Alvarez
Keyword(s):  
Main Chain ◽  
Effective Interaction ◽  
Thermal Studies ◽  
The Other ◽  
Spectroscopic Techniques ◽  
Aromatic Diamines ◽  
Packing Factor ◽  
Degradation Temperature ◽  
General Terms ◽  
Acid Dichloride

AbstractTen poly(amide) oligomers were prepared from four acid dichlorides and two full-aromatic diamines, the latter containing silicon or germanium in their structure. The polymers, which contain Et/Me, Et/Et and nBu/nBu combinations on heteroatom of the acid dichloride moiety, were characterized by spectroscopic techniques, including 29Si NMR. The yields obtained and the ηιnh values established were low, indicating the low molecular weight nature of the polymers. Thermal stability was also evaluated by TG and DSC techniques. When a methyl group was replaced by a Et, the Tg of the poly(amides) (PAs) was increased in accordance with the gain in the flexibility of the chain. However and in general terms, the PAs with nBu groups show the inverse effect. Probably, the possibility of an effective interaction between these side chains affects negatively the flexibility of the main chain. On the other hand, PAs that contain single silicon in their structure show lower Tg values than the Ge-containing PAs. For the other heteroatom combinations, similar results were obtained. This fact does not agree with the lower size of silicon atom which should increase the molecular rigidity and therefore their Tg values. Probably, the influence of the side groups is decisive in hindering the chain rotation. The thermal degradation temperature (TDT) changed in agreement with the packing factor of the chains which was depending on the size of substitute groups. So, when Et group was replaced by nBu as lateral group, lower TDT were recovered. With respect to the heteroatoms used in the main chain, the TDT values do not show a clear tendency.

scholarly journals Statistical analysis of chromosome distribution to the poles in interspecific hybrids with variable chromosome pairing

1963 ◽  
Vol 4 (2) ◽  
pp. 266-275 ◽  
Author(s):  
A. G. Sficas
Keyword(s):  
Statistical Analysis ◽  
Interspecific Hybrids ◽  
Random Distribution ◽  
The Other ◽  
Meiotic Pairing ◽  
Variable Amount ◽  
Short Discussion ◽  
Equal Distribution ◽  
Chromosome Separation ◽  
Opposite Tendency

A probability distribution of chromosome separation to the poles was developed to test the randomness of movement of univalents in asynaptic material where a variable amount of meiotic pairing occurs. Two tables were calculated, one for 24 chromosomes which can be used for any even number equal or less than 24, and the other for 19 chromosomes which can be used for any odd number equal or less than 19.Three Nicotiana hybrids, namely N. glutinosa × N. otophora, N. glutinosa, N. sylvestris, and N. tabacum × N. glutinosa, and one polyhaploid were investigated. All hybrids had a tendency towards an equal distribution of unpaired chromosomes to the poles. The polyhaploid N. tabacum (with a substituted N. plumbaginifolia chromosome) had an opposite tendency, i.e. towards a flatter distribution than expected from random distribution of univalents. A short discussion of the problem is given.

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