ISSN:0258-0322    

DOI:10.1002/masy.19860010102

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0258-0322    

DOI:10.1002/masy.19860010103

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractQualitative discrepancies are found between what is predicted by available theory and what is actually observed, for several concentration regimes of the dynamical properties of polymer solutions. The difficulties are most severe, from the standpoint of experiment or simulation as well as theory, for the entanglement concentration regime. However, the classical problems of chain polymers in dilute solution are not fully understood. For example, the constants of proportionality that relate hydrodynamic radii to the radius of gyration, in the nondraining limit and in theta solvents, may not be universal constants. That is, the proportionality constants may vary with polymer and solvent species. Discrepancies between theory and experiment are discussed for the two different systems, dilute chains and semidilute rods. Speculation is offered on the resolution of these difficulties.

ISSN:0258-0322    

DOI:10.1002/masy.19860010104

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper describes recent developments in polymerization of cyclic imino ethers, 2‐oxazolines and 5,6‐dihydro‐4H‐1,3‐oxazines, which have been performed mainly in our laboratory. Cationic ring‐opening polymerizations of these two kinds of monomers gave poly(N‐acylethylenimine)s and poly(N‐acyltrimethylenimine)s, whose hydrolysis produced linear poly‐ethylenimine and poly(trimethylenimine), respectively. The mechanism of the polymerization is mainly governed by the nature of monomer and of the counter anion derived from initiator. There are two types of stable propagating species; cyclic onium species and covalent alkyl halide species. In a specific case, e.g., the polymerization of 5‐methyl‐2‐oxazoline with MeI initiator, both ionic and covalent species are involved in equilibrium and propagate concurrently. Then, a new terminology of “Electrophile Polymerization” has been proposed as a broader expression including cationic and covalent propagating species. By utilizing living nature of the cyclic imino ether polymerization, block copolymerizations between these monomers were performed. A poly(cyclic imino ether) chain becomes hydrophilic or lipophilic depending on the monomer. Product AB and ABA type block copolymers were soluble in water and showed excellent surface properties reflected by values of surface tension (γ), when A (or B) and B (or A) are hydrophilic and lipophilic. Thus, various nonionic polymer surfactants of block and graft type have been prepared from cyclic imino ethers. Finally, poly(N‐acetylethylenimine) chain showed good compatibility with poly(vinyl chloride). Cellulose diacetate and poly(vinyl chloride) are not miscible, but cellulose diacetate g‐poly(N‐acetylethylenimine) is miscible with poly(vinyl chloride), the graft

ISSN:0258-0322    

DOI:10.1002/masy.19860010105

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractAfter an introduction describing the development of1H,2H, and13C solid state NMR two sections on13C and2H NMR, respectively, outline the physical background as related with molecular motion. Some representative examples demonstrate the potential of recent NMR techniques in polymer dynamics studies.

ISSN:0258-0322    

DOI:10.1002/masy.19860010106

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractInvestigations over the past decade have disclosed that the structure of DNA in solution is far from uniform and static. The present view of DNA structure is that it is: 1) dynamically variable, displaying relatively large flexibility in both bending and torsional modes, 2) it is not perfectly helical because of sequence dependent departures from a regular helix and 3) it is capable of adopting entirely different conformations, including a switch in the sense of the helix as is the case for the B to Z transition, as well as new folding patterns as is the case for cation induced DNA collapse.One of the principal problems in the field today is the detection and evaluation of structural changes in solution. Many experimental techniques are in use and a number of these will be reviewed. The discussion includes models of flexible DNA, the structural aspects revealed by several experimental techniques, and results for a number of systems in which solution environment brings about changes in structure.

ISSN:0258-0322    

DOI:10.1002/masy.19860010107

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe solute structure in concentrated polyelectrolyte solutions is discussed in terms of the following observations:1) The broad peak in the global structure function measured by radiation scattering (neutron, X rays or light), in the interval q<2 nm−1,2) The separate intra and intermolecular structure functions obtained by neutron scattering,3) The separate polyion‐counterion partial structure factors derived from neutron scattering,4) The variation with wave vector of neutron and light quasi‐elastic broad

ISSN:0258-0322    

DOI:10.1002/masy.19860010108

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractSeveral new reactive polymers containing various nitrogen functionalities have been prepared in bead form and tested as catalysts or ligands for reactive moieties in organic synthesis. In particular polymers containing 4‐dialkylaminopyridine pendant groups show good to excellent catalytic activities depending on their structure and their microenvironment. Best results are obtained on polystyrene backbones when the catalytic species are removed from the styrene rings by a three carbon spacer. Poly‐benzimidazole resins prepared by precipitation polymerization are good ligands for transition metal catalysts used in the catalytic hydrogenation of nitro compounds or olefinic double‐bonds. The PBI resins can also be used to prepare a polymeric oxidizing reagent through the binding of Cr(VI); the reagent oxidizes alcohols to the corresponding carbonyls while spent Cr(II) or Cr(III) remains anchored to the polymer. Other polymers containing chiral amino‐alcohol pendant groups show useful properties as chiral auxiliaries in the asymmetric reduction of ketones using polymer‐complexed lithium aluminiu

ISSN:0258-0322    

DOI:10.1002/masy.19860010109

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractChemical binding or strong complexing of individual antigens (proteins, polysaccharides) or antigenic determinants with non‐natural membrane active polyelectrolytes results in formation of effective immunogens with high protective properties. These artificial antigenic conjugates develop strong immunogenicity also in the absence of T‐cells. The strength of the immune response is not controlled by Ir‐genes. An antigenic moiety of a conjugate is responsible for its “focusing” on B‐lymphocytes of the proper clone. Linear polyion moiety being adsorbed on the cell membrane surface aggregates membrane proteins and induces nonspecific transmembrane ionic permeability. K+‐flux from the cell and Ca+2‐flux into the cell disturb cell homeostasis and thus, pull trigger mechanism of K+, Na+‐ATPase and Ca+2‐ATPase activity. Then the cell synthesizing apparatus starts to operate. The covalent conjugates of Salmonella typhimurium and influenza A‐virus individual antigens with synthetic polyelectrolytes seem to represent a new generation of vacci

ISSN:0258-0322    

DOI:10.1002/masy.19860010110

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractWe Have Measured Directly The Forces Between Two Smooth Solid Surfaces Immersed In Liquid Media In The Range Of Surface Separation 0 ∼ 2000Å. By Measuring The Interactions Both With And Without Polymers Adsorbed Onto The Surfaces From The Solution, We Could Characterize The Effects Due To The Adsorbed Polymers Themselves. This Has Been Done For Several Model Polymer Systems In A Wide Range Of Solvency Conditions: Poor‐, Theta‐ And Good Solvents, As Well As For Charged Polymers In Ionic Media. The Present Paper Describes Two Recent Studies Of Adsorbed Polymers In Theta‐Solvent And Good Solvent Conditions, And The Effect Of Polymer Bridging At Low Adsorbance Values. The Experimental Studies Are Extremely Direct, And Can Be Compared With Molecular Models: We Briefly Describe Such A Detailed Comparison For The Case Of Interaction Between Adsorbed Polymer Layers In A poor

ISSN:0258-0322    

DOI:10.1002/masy.19860010111

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY