摘要:

AbstractMono‐ and dicationically living poly(1,3‐dioxolane) (pdxn) and poly (1,3‐dioxepane) (pdxp) were obtained with CF3SO3H (trifilic acid‐tfac) and (CF3SO2)2O (triflic anhydride‐tfan), respectively. Concentration of the active species and living character of polymers were established by applying the ion‐trapping technique. Addition of a second cyclic acetal to the living bifunctional polyacetal (e. g. addition of dxn to pdxp) leads to the formation of a block copolymer (according to13C NMR), but before the second monomer polymerizes completely, the transacetalization process leads to the conversion of the internal homoblock to a more or less (depending on time) statictical copolymer. Thus, competition of the homopropagation and transacetalization is not in favor of formation of the block copolymers with pure homoblocks, at least when the second block, built on the already existing homoblock, is formed slower than the homoblock is reshuffled by transac

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830401

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractA series of homo‐oligomeric peptides derived fromγ‐benzyl‐L‐glutamate, Nps‐[L‐Glu‐(OBzl)]n+m−OBzl(4(n,m)) (n+m= 2 to 12, 15, 16, 18, 21, and 24), were synthesized for the first time by the DCC‐ONSu method using and activated easter. The identification and conformation of these peptides in cast films were investigated successfully by IR spectroscopy. It was found that the formation of the β‐structure begins with the tetrapeptide, and that of the α‐helix in the range from the hexapeptide to octapeptide. There is some evidence for small quantities of other conformational nuclei which may coexist as preferred conformations in peptides between the hexa‐ and decapetides. These effect cannot be attributed to sample purity since they could be sho

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830402

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractCopolymerization of acrylamide with allyl glycidyl ether yielded water soluble polymers containing an epoxy group; addition of a crosslinking agent,N,N′‐methylenebis(acrylamide), to the copolymerization mixtures resulted in the formation of similar though water insoluble polymers. Condensation of a potent beta‐adrenergic antagonist AlmH, which contains a reactive amino group, with a polymer containing an epoxy group yeilded a pharmacologically active polymer. The polymer containing the epoxy group was also converted, by reaction with sodium thiosulfate and subsequent reduction, into a mecapto groups containing polymer which was also water soluble. The latter polymer was converted by condensation with a beta‐adrenergic antagonist AlmCOCH2Br, which contains a reactive bromoacetamido group, into a pharmacologically act

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830403

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractSoluble polymer with methylene‐1,4‐dioxane‐2,3‐diymethylene (75 − 65 mole‐%) and 2‐[(vinyloxy)ethoxy]ethylene structural units (25 − 35 mole‐%) were obtained in the radical polymerization of ethylene glycol divinly ether (EGVE) in benzene at conversions of about 30 – 45%. It was found that in the radical polymerization of EGVE the rate of polymerization is proportional to the 1,5th power of monomer concentration and to the 0, 6th power of initiator concentration. On the other hand, a soluble polymer with 1,4‐dioxepane‐5,7‐diylmethylene units was obtained from cationic polymerization of EGVE in dichloromethane by using iodine as as catalyst. Moreover, the photocrosslinking reactions by irradiation with UV light of the radically obtained polymer having pendant vinyloxy groups with dithiols or by diazonium tetrafluro

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830404

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractAromatic heterocyclic polymers are exceedingly attractive high performance materials because of their unusually high mechanical strength, chemical resistance and thermal stability, but are very difficult to process unless “swivel” atoms or groups are inserted along the chains to increase conformational flexibility. The present theoretical investigation employs the CNDO/2 method with direct geometry optimization to calculate such flexibility for the wholly aromatic swivels biphenyl, 2,2′‐bipyridyl, 2‐phenylpyridine, 2,2′‐bipyrimidyl, and 2‐phenylpyrimidine. The most important result is the prediction that both flexibility and accessibility of coplanar conformations should increase significantly with the number ofortho‐CH groups replaced by N‐atoms. The calculations also provide information on other conformation‐dependent properties such as optimized geometries, charge distributions, and dipole moments, and these results are found to be in satisfactory agreement with the results of previous theoretical and experimental studies. Finally, since these chains are soluble only in strongly acidic media, the species mono‐ and diprotonated 2,2′‐bipyridyl, 2,2′‐bipyridyl · H3O+, and 2,2′‐bipyrimidyl · 2H2O were also investigated with regard to some of

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830405

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe compact → coil conformational transition of hydrophilic‐hydrophobic copolymers derived from poly(methacrylic acid) was studied by UV Spectroscopy. Two copolymers were used in this study: a Poly(N‐methacryloylalanine‐co‐N‐phenylmethacrylamide) (P50) and a poly(methacrylic acid‐co‐benzyl methacrylate) (S25). Both samples exhibit hypochromism in the absorption band of the aromatic chromophore when they are under the compact conformation: 7% and 30% hypochromism for P50 and S25, respectively. This difference is explained by differences in the hydrophobic side chain‐side chain interactions between the aromatic residues. Increasing the temperature was found to increase strongly the hypochromism of S25 and to have lit

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830406

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe compact → coil conformational transition of two series of hydrophilic‐hydrophobic copolymers derived from poly(methacrylic acid) was studied by potentiometric and conductimetric titrations. The samples used were poly(N‐methacryloylalanine‐co‐N‐phenylmethacrylamide) containing up to 50 mole‐% of the hydrophobic residue (P series) and poly(methacrylic acid‐co‐benzyl methacrylate) containing up to 25 mole‐% of the hydrophobic residue (S series). The determination of the free enthalpy of the transition and of the domain of the degree of ionization in which the transition occurs, show inportant differences in the behaviour of the two series of copolymers. These differences are explained by an entropy‐enthalpy compensation for the S series due to strong hydrophobic interactions between the aromatic side chains. Conductimetric titrations allow, in some cases, the determination of the degree of ionization at the beginning and at the end of the conf

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830407

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractMeasurements of the solubilization of a water insoluble compound, azobenzene, inside the hydrophobic domains of compact conformations, were carried out using different polymers and copolymers. The influence of the tacticity of the polymer and the hydrophobic character of the copolymers was investigated, as well as specific intramolecular interactions between the hydrophobic residues. The influence of the solubilization on the spectral properties (λmaxand εmax) of azobenzene and the copolymers was also studied. Experimental results show that no close correlation exists between the solubilizing power and the stability of the compact conformation, especially since some copolymers which take a compact conformation have no solubilizing powe

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830408

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe interaction of heparin with salmine protamine was investigated using the electrostatically bound fluorescent probes acridine orange and eosin Y and the 1‐(dimethylamino)‐5‐naphthalene sulfonyl group which is covalently bound to the protamine molecule. Dye displacement experiments indicate a 1 : 1 pairing of anionic heparin sites with cationic protamine sites. Further binding of heparin occurs, after all the cationic sites of protamine are bound up with heparin. This is thought to occur as a result of the different affinities of the sulfate and carboxyl groups of heparin for guanidino groups; the sulfate groups binding preferentially to the complex releasing some of the bound carboxyl groups. Fluorescence polarisation measurements suggest a heparin‐protamine complex greater in volume than would be expected from a simple pairing of heparin and protamine molecules, indicating some degree of cross‐linking. The limiting salt concentrations for the heparin‐protamine complex were determined in the prescence of a number of Group IA and IIA meta

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830409

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe free radical polymerization ofN‐vinylcarbazole (VK) was investigated in hexane, nonane, toluene, HMPT, DMF, DMAC, and DMSO. Isotactic propagation was found to be energetically favoured by between 1500 and 4600 J · mol−1for all the solvents investigated, although the entropy difference between syndiotactic and isotactic propagation strongly favoured syndiotactic propagation by between 11 and 20 J · mol−1K−1. Variation in the steric microstructure between an isotactic mole fraction of 0,25 and 0,47 was obtained by varying the polymerization temperature and solvent. The activation enthalpy differences between isotactic and syndiotactic propagation (ΔH≠s/i− ΔH≠i/s), for the free radical polymerization of methyl methacrylate (MMA) and VK were compared and the steric configurations involved in the propagation process considered. It was concluded that electronic interaction between radical and monomer appeared to determine the energetic preference of the growing chain for isotactic or syndiotactic propagation in free radical propagation. This energetic preference was correlated with thee‐factor in theQ−escale. Data for the free radical polymerization of VK, MMA, and vinyl trifluoroacetate showed that solvent polarity has a weak influence on the energetic preference of the growing chain for isotactic or syndiotactic propagation. This energetic preference was correlated with the π*

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830410

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY