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  • 1
    Electronic Resource
    Electronic Resource
    Radical copolymerization behaviors of styrene and coumarin (1994)
    Springer
    Journal of polymer research 1 (1994), S. 295-303 
    Details
    ISSN: 1572-8935
    Keywords: Coumarin ; 7-Acetoxycoumarin ; Radical copolymerization ; Monomer reactivity ratio ; Terminal model ; Penultimate model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The radical copolymerizations of styrene (M1) with coumarin (M2) (and 7-acetoxycoumarin) have been first carried out in benzene (and in DMF) at 60° C using AIBN as initiator. The terminal model monomer reactivity ratios (MRR) were determined by Fineman-Ross method, Kelen-Tudos method and nonlinear method. The respective estimated values are r1 = 43.08, r2 = 0.63; r1 = 39.17, r2 = 0.43; and r1 = 49.94, r2 = 1.04 for styrene-coumarin (S-C) system. For styrene-7-acetoxycoumarin (S-AC) system, the values are r1 = 51.44, r2 = 1.24; r1 = 50.56, r2 = 1.20 and r1 = 56.23, r2 = 1.48, respectively. The penultimate model MRRs are determined by Fenn-Barson method and nonlinear method to be r1= 49.18, r1′ = 2.01, r2 = r2′ = 0.43 and r1 = 51.21, r1′ = 0.86, r2= r2′ =0, respectively, for S-C system; r1 = 64.76, r1′= 3.46, r2 = r2′= 1.20 and r1 = 59.90, r1 = 0.57, r2 = r2′ = 0. respectively, for S-AC system. It is found that coumarin is about 1.2 times more reactive toward styrene-terminated radical than 7-acetoxycoumarin for steric reasons. The penultimate model of Fenn-Barson is fairly adequate in describing the copolymerization mechanism of styrene-coumarin system, while the terminal model is more suitable for styrene-7-acetoxycoumarin system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01374554
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of polyesters containing coumarin dimer components by photopolymerization of 7,7′-coumarinyl polymethylene dicarboxylates (1994)
    Springer
    Journal of polymer research 1 (1994), S. 285-293 
    Details
    ISSN: 1572-8935
    Keywords: 7,7′-Coumarinyl polymethylene dicarboxylate ; Photopolymerization ; Coumarin dimer ; Polyester, Cyclobutane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Eight 7,7′-coumarinyl polymethylene dicarboxylates have been successfully synthesized by solution condensation of 7-hydroxycoumarin (umbelliferone) or 7-hydroxy-4-methylcoumarin (4-methylumbelliferone) with various polymethylene diacid chlorides. Upon benzophenone-sensitized irradiation with 350 nm light, the terminal coumarin chromophores dimerize to form intermolecular cycloadducts or intermolecular polyesters with three kinds of cyclobutanes (syn head-to-head,anti head-to-head,anti head-to-tail), depending on structure of the dicarboxylates and reaction conditions. The structures of the cycloadducts and polyesters have been characterized by1H NMR spectra. When the methylene units exceed seven, intermolecular reaction becomes predominant and result inanti-rich configuration photo-cyclized products with higher viscosity. Lower polar solvents and 4-methyl substitution in coumarin chromophores also promote intermolecular reaction. The highest viscosity (ηred = 0.42 dL/g) is obtained with polyester from 7,7′-(4-methyl coumarinyl) decamethylene decarboxylate. Irradiation of the polyesters with 254 nm light leads to symmetric cleavage of the cyclobutane linkage in the main chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01374553
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  • 3
    Electronic Resource
    Electronic Resource
    Solid-phase synthesis of larger peptides by a new strategy of detachment from the resinThe abbreviations for amino acids and widely used blocking groups are those defined by the IUPAC-IUB Commission on Biochemical Nomenclature (1972) Eur. J. Biochem. 27, 201-207. (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 1833-1843 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attachment of the side-chain carboxyl of the protected aspartic or glutamic acid ester to the resin support has been established for the solid-phase synthesis of the asparagine or glutamine peptide. After further elongation of the α-amino deprotected resin-bound peptide ester with protected peptide fragments and the final detachment from the resin support by ammonolysis, the larger peptides containing, or preferably C-terminated with, asparagine or glutamine could be obtained. Thus, the C-peptide of human proinsulin was prepared by coupling to the resin-bound dipeptide derivative, Leu-Glu(OCH2Ph®)·OtBu, with six fragments consecutively. It was obtained in an overall yield of 36% after detaching from the resin with alcoholic ammonia, followed by mild acidolysis, DEAE cellulose chromatography, and gel filtration. This procedure has now been applied to the synthesis of the C-terminal fragment of the insulin A chain ending in asparagine, and also to the synthesis of the threonine or serine peptide, where the anchorage to the resin was designed by the reaction of the sidechain hydroxyl with succinic anhydride in the presence of 4-dimethylaminopyridine to form the hemiester of succinic acid, which in turn was condensed to the aminomethyl resin by the DCC-HOBt procedure. Model experiments on the synthesis of the Z-Thr(CO-CH2CH2CONHCH2Ph®)·OtBu and Bpoc-Lys(Boc)-Thr(COCH2CH2CONHCH2Ph®)·OtBu, as well as their detachment from the resin by amminolysis or hydrazinolysis, have shown the potential for a milder process in the solid-phase synthesis of larger peptides.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360200908
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation and photoreaction of copolymers derived from N-(1-phenylethyl)acrylamide and 7-acryloyloxy-4-methyl coumarin (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1867-1875 
    Details
    ISSN: 0887-624X
    Keywords: N-(1-phenylethyl)acrylamide ; 7-acryloyloxy-4-methyl coumarin ; copolymerization ; monomer reactivity ratio ; photocrosslinking ; photocleavage ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copolymers containing photoreactive 4-methyl coumarin pendant groups have been prepared by radical copolymerization of N-(1-phenylethyl)acrylamide (M1) and 7-acryloyloxy-4-methyl coumarin (M2) in DMF at 70°C. The monomer reactivity ratios (MRR) of M1 and M2 are estimated by Finenam-Ross, Kelen-Tüdos, Mayo-Lewis, and YBR methods to be about r1 = 0.12-0.16 and r2 = 1.13-1.28. Dilute dioxane solutions of the copolymers (10-4-10-5 M of 4-methyl coumarin chromophores) are first photocrosslinked intramolecularly by irradiating 350 nm light (dimerization of 4-methyl coumarin) and then photo-cleaved at 254 nm (symmetric cleavage of cyclobutane). Tracing by an UV-visible spectrophotometer, it is found that photocrosslinking and photocleavage proceed simultaneously when 254 nm is the light source and finally reaches to a dynamic equilibrium. However, only photocrosslinking can be observed under 350 nm light. Kinetic results show that both photocrosslinking and photocleavage are first-order reactions. Moreover, photocrosslinking rate constant increases with mole fraction of M2 in the copolymer (F2). On the contrary, rate constant of photocleavage decreases with increasing F2. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321007
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  • 5
    Electronic Resource
    Electronic Resource
    Photopolymerization of 7,7′-coumarinyl polymethylene dicarboxylates: Fluorescence and kinetic study (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2999-3008 
    Details
    ISSN: 0887-624X
    Keywords: 7,7′-coumarinyl polymethylene dicarboxylate ; photopolymerization ; fluorescence ; coumarin ; dimerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All eight 7,7′-(4-methylcoumarinyl) polymethylene dicarboxylates (3, 4) containing terminal photoreactive coumarin chromophores show strong fluorescence intensities at room temperature in dimethyl sulfoxide (DMSO) and CH2Cl2. After irradiation with 350 nm light for 2 h, the fluorescence characteristics of the dicarboxylates reveal their photopolymerization paths. On irradiation of the unsubstituted dicarboxylates (3) in DMSO, singlet excited state excimers are formed, leading to syn head-to-head coumarin dimer configuration. However, for all dicarboxylates in CH2Cl2, the dimerization of the coumarin chromophore proceeds via a triplet excited state in the presence of benzophenone to form the anti-configuration photoproducts. Further confirmations of the reaction mechanism are made by kinetic studies. At high concentration, photopolymerization of 7,7′-(4-methylcoumarinyl) polymethylene dicarboxylate (4c) obeys zero-order and first-order kinetics for coumarin chromophore and benzophenone, respectively. This is a powerful proof of the proposed mechanism of a triplet excited state reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2999-3008, 1997
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Linear dichroism induced by the photocleavage of polyamides containing cyclobutane rings (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 3397-3401 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1988.080261222
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  • 7
    Electronic Resource
    Electronic Resource
    Hydroxypropyl cellulose (HPC)-stabilized dispersion polymerization of styrene in polar solvents: Effect of reaction parameters (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2765-2772 
    Details
    ISSN: 0887-624X
    Keywords: dispersion polymerization ; hydroxypropyl cellulose ; steric stabilizer ; nucleation ; particle growth ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dispersion polymerization of styrene in polar solvents in the presence of hydroxypropyl cellulose (HPC) produces latex particles from ca. 1 to 26 μm depending on reaction parameters. Increasing the initiator concentration or temperature decreases the molecular weight, but increases the particle size and breadth of the size distribution. The decrease in molecular weight with increasing Ri, caused by larger initiator concentration or higher temperature, is expected based of fundamental kinetic relationships. The inverse correlation between size and rate of initiation is rationalized by polarity (stabilizing ability) of the grafted HPC-polystyrene formed in situ. High polar HPC-g-PS, which contains shorter graft polystyrene chain, stabilizes particles less effectively and this leads to larger particles. The primary influence of initial styrene concentration is a solvent effect: larger particles are obtained at high styrene concentration due to high solubility of polystyrene during the initial part of the reaction. The influence of the molecular weight of HPC is to change the polarity of the HPC-g-PS stabilizer. Comparison of particle growth of three critical polymerization systems suggests that the favorable continuous-phase solubility parameter for dispersion polymerization of styrene is around 11.6 (cal/mL)1/2. Too high or too low polarity generates particles with broad size distribution because large particles are formed during the initial stage and nucleation continues as the polymerization proceeds. © 1992 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301312
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  • 8
    Electronic Resource
    Electronic Resource
    Reversible photodimerization of coumarin derivatives dispersed in poly(vinyl acetate) (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2705-2714 
    Details
    ISSN: 0887-624X
    Keywords: coumarin derivatives ; photodimerization ; photocleavage ; reversible ; pho-tosensitizer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four photoreactive coumarin derivatives were successfully synthesized from 7-hydroxy-coumarin and 7-hydroxy-4-methylcoumarin, i.e., 7-propionyloxy-4-methylcoumarin (M1), 7-palmitoyloxy-4-methylcoumarin (M2), 7-propionyloxycoumarin (M3), and 7-palmitoy-loxycoumarin (M4). Reversible photodimerization (350 or 300 nm) and photocleavage (254 nm) of these coumarin derivatives dispersed in poly(vinyl acetate) (PVAc) were investigated by tracing their UV absorbance variations at 310 nm. The M2 and M4 with long palmitoyl chain show much better photoreaction reversibility than M1 and M3 with short propionyl chain. Moreover, photodimerization rate (under 350 nm) of M2 is greater than 200 times of that of M1. This has been explained by the formation of suitable conformation for revers-ible photodimerization due to the hydrophobic interactions. Photodimerization of M2 is ca. 3 times quicker than that of M4, indicating 4-methyl substitution enhances pho-todimerization. The influence of photodimerization wavelength (350 and 300 nm) and photosensitizer (benzophenone) have also been investigated in detail. © 1995 John Wiley & Sons. Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331604
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, and chiroptical property of optically active poly(urea-urethane)s (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1719-1727 
    Details
    ISSN: 0887-624X
    Keywords: (1S,2S)-(+)-2-amino-3-methoxy-1-phenyl-1-propanol ; optically-active poly(urea-urethane) ; DSC ; TGA ; circular dichroism spectra ; direct resolution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five new optically active poly(urea-urethane)s were synthesized by solution polyaddition of (1S,2S)-(+)-2-amino-3-methoxy-1-phenyl-1-propanol (4) with diisocyanates (diphenylmethane-4,4′-diisocyanate, toluene-2,4-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, m-xylylene diisocyanate) at 80°C for 60 h. In some cases, the reaction mixture transformed into a gel when cooled to room temperature. The reduced viscosities are between 0.14 and 0.63 dL/g depending on the solvents and diisocyanates. Thermal behaviors of these polymers were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The Tg and crystallization temperature (Tc) were in the range of 80-200°C and 220-238°C, respectively. Thermal decomposition started at about 275°C, and the residual weights at 400°C were 15-60% depending on the polymers. The conformation of the polymers in film state was studied by circular dichroism (CD) spectra, by comparison with the corresponding model compounds which were synthesized from 4 and phenyl isocyanate or propyl isocyanate. Polymers derived from aromatic diisocyanates formed as ordered conformation in the film state, while those from aliphatic diisocyanates did not. After packing as chiral stationary phases of high-performance liquid chromatography (HPLC), the polymers showed selective resolution to trans-stilbene oxide and trans-1,2-cyclopentanedicarboxanilide. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310710
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and reversible photocleavage of novel polyurethanes containing coumarin dimer components (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 613-624 
    Details
    ISSN: 0887-624X
    Keywords: anti head-to-head 7-hydroxycoumarin dimer ; anti head-to-tail 7-hydroxy-4-methylcoumarin dimer ; polyurethane ; photocleavage ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six polyurethanes containing coumarin dimer components in the main chain have been prepared by polyaddition of diisocyanates with anti head-to-head 7-hydroxycoumarin dimer or anti head-to-tail 7-hydroxy-4-methylcoumarin dimer. 7-Acetoxycoumarin and 7-acetoxy-4-methylcoumarin were first prepared and then photodimerized under 350 nm UV light to give anti head-to-head 7-acetoxycoumarin dimer and anti head-to-tail 7-acetoxy-4-methylcoumarin dimer, respectively. After hydrolyzing under acidic conditions to 7-hydroxycoumarin dimer and anti head-to-head 7-hydroxycoumarin dimer, they were polymerized with aliphatic and aromatic diisocyanates in N,N-dimethylacetamide to give the polyurethanes. Addition of dibutyltin dilaurate (T-12) as catalyst increases the polymer yield with the viscosity remaining almost unchanged. It was also found that lithium chloride enhances both the yield and viscosity of the polyurethanes by increasing their solubility possibly through complexation. The polyurethanes are symmetrically photocleaved at cyclobutane rings under 254 nm UV light to dicoumarins. Reversible photodimerization of the photocleaved compounds have also been investigated under 300 and 350 nm UV light. The polyurethanes from aromatic diisocyanates or with 4-methyl substituent exhibit greater reactivity in the photocleavage reaction. © 1997 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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