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  • 1
    Electronic Resource
    Electronic Resource
    Catalytic chain transfer for molecular weight control in the emulsion homo- and copolymerizations of methyl methacrylate and butyl methacrylate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 859-878 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of catalytic chain transfer in semi-batch emulsion polymerization has been studied for two monomers, viz, methyl and n-butyl methacrylate. Two different catalytic chain transfer reagents were used with different water solubilities: cobaloxime boron fluoride (COBF), which was found to partition approximately equally between organic and aqueous phases, and tetra-phenyl cobaloxime boron fluoride (COPhBF), which was found to reside predominantly in the organic phase. The difference in hydrophilicity between the two transfer agents was found to affect the polymerization mechanism. COBF exhibited superior transfer behavior in all cases, whereas the restricted mobility of the COPhBF had a deleterious effect on the efficiency of the transfer mechanism. The best results were achieved under monomer flooded conditions using COBF. MALDI-TOF mass spectrometry analysis shows catalytic chain transfer to be the dominant mechanism initiating and stopping chain growth as none of the chains appear to have initiator fragment end groups. Analysis of copolymers by MALDI-TOF mass spectrometry reveals both molecular weight and composition data. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 859-878, 1997
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of propagation rate constants for the copolymerization of methymethacrylate and styrene using a pulsed laser technique (1989)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 27 (1989), S. 181-185 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1989.140270601
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  • 3
    Electronic Resource
    Electronic Resource
    Copolymerization kinetics of 4-methoxystyrene with methyl methacrylate and 4-methoxystyrene with styrene: A test of the penultimate model (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 2097-2106 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The propagation kinetics for the copolymerization of 4-methoxystyrene with methyl methacrylate and 4-methoxystyrene with styrene have been investigated using a pulsed laser technique. The dependence of the copolymerization propagation rate constant on the monomer feed ratio shows a diviation from classic Mayo-Lewis model kinetics for 4-methoxystyrene with methyl methacrylate but not for 4-methoxystyrene with styrene. These results have been interpreted to indicate that a penultimate effect is apparent in the first monomer pair but not in the second. With r1r2 = 0.092 for the copolymerization of 4-methoxystyrene with methyl methacrylate and r1r2 = 0.95 for 4-methoxystyrene with styrene, it is suggested that a deviation of the product of the coplymerization reactivity ratios from unity may be an indication of the presence of a penultimate effect.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280807
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of solvent on the homo-propagation rate coefficients of styrene and methyl methacrylate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2311-2321 
    Details
    ISSN: 0887-624X
    Keywords: styrene ; methyl methacrylate ; pulsed-laser polymerization ; “living” free radical ; propagation rate coefficient ; solvent effects ; benzyl alcohol ; N-methyl pyrrolidinone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The free radical propagation rate coefficients of both Methyl Methacrylate (MMA) and Styrene (STY) have been measured using Pulsed-Laser Polymerization. The effect of solvents on the propagation rate coefficient, kp, is reported for several solvents, namely, bromobenzene, chlorobenzene, dimethyl sulphoxide, diethyl malonate, diethyl phthalate, benzonitrile, and benzyl alcohol, at 26.5°C. This preliminary data indicated that benzyl alcohol (BzA) had a large effect on the MMA propagation reaction. As earlier work indicated that N-methyl pyrrolidinone (NMP) would also have a large effect on the kp of MMA, Arrhenius parameters were evaluated for both MMA and STY at two different concentrations of monomer in BzA and NMP. BzA had a significant effect (at 95% confidence) increasing both the activation energy (Ea) and the preexponential factor (A) for MMA and STY. In NMP, a similar trend is observed for MMA polymerization; however, while a solvent effect on STY was observed, the effect on Ea and A was too small to discern with confidence. A series of additional experiments was performed to evaluate the influence of camphorsulfonic acid (CSA) as an additive in STY polymerization. There was no effect of CSA on kp, confirming that the strong effect CSA has on “living” radical polymerization of styrene does not originate from complexation leading to an accelerated propagation step but rather by altering the ratio of active-to-dormant chains in the reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2311-2321, 1997
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of porous hydrogel structures by polymerizing the continuous phase of a microemulsion (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 219-226 
    Details
    ISSN: 0959-8103
    Keywords: microemulsion ; hydrogel ; poly(2-hydroxyethyl methacrylate) ; equilibrium water content ; oxygen permeability ; scanning electron microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of microemulsions have been formulated, with 2-hydroxyethyl methacrylate (HEMA) or HEMA/water/propanol mixtures as the continuous phase and methylcyclohexane as the discontinuous phase. The effect of surfactant type was investigated with the utilization of both anionic and nonionic surfactants. The microemulsion continuous phase was polymerized by UV radiation and a thermal post-cure. The resultant polymers were extracted to remove the discontinuous phase and the surfactant. On swelling, the majority of the polymers became opaque, although transparent PHEMA hydrogels were synthesized with an improved equilibrium water content (EWC). The cause of opacity was shown by field emission scanning electron microscopy (FESEM). The breakdown in the microemulsion on polymerization is caused by unfavourable interactions between the PHEMA and the stabilizing surfactants causing agglomerization of the discontinuous phase. All the hydrogels were found to have higher water retention than PHEMA, with EWCs of up to 70%. The modified polymers also demonstrated an increased rate of water diffusion into the matrix. A preliminary study of oxygen permability revealed that a significant improvement had been made over standard PHEMA membranes. The porous structure of the PHEMA gels has been shown to be dependent on the type of surfactant used during synthesis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360301
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  • 6
    Electronic Resource
    Electronic Resource
    Application of dielectric spectroscopy and DSC to the study of relaxations in some copolymeric hydrogels (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 397-404 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The nature of water in copolymeric N-vinyl pyrrolidone/methyl methacrylate hydrogels has been investigated using dielectric thermal analysis (DETA) and differential scanning calorimetry (DSC). Dielectric tan δ measurements are reported over a frequency range 500 Hz-20 kHz and a temperature range of -140 to +20°C. The observed complex relaxations were attributed to the mobility of water and the relaxation processes of the copolymer matrix. In addition DSC was used to measure the melting endotherm of water in gels partially swollen to a pseudoequilibrium. The resultant data were fitted to a two-phase approximation model. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560310
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  • 7
    Electronic Resource
    Electronic Resource
    Studies on the application of matrix-assisted-laser-desorption-ionisation time-of-flight mass spectrometry to the determination of chain transfer coefficients in free radical polymerization (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2403-2408 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chain transfer coefficient (Cs) has been determined for 2-methyl-2-propanethiol (t-Bu-SH) in the solution polymerization of methyl methacrylate (MMA). Three different analytical methods were investigated. The Mayo and chain length distribution (CLD) methods yielded consistent Cs values of 0.12 and 0.13, respectively, at 60°C. A third, new approach to the evaluation of Cs values was also attempted using Matrix-Assisted-Laser-Desorption-Ionisation (MALDI) Time-Of-Flight Mass Spectrometry to analyse the end-groups of the polymer chains. The values of Cs obtained from MALDI analyses were not consistent with the other two methods and the relative intensities of the peaks with different end-groups were found to be dependent on the selection of cation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Observations on the swelling behaviour of copolymeric hydrogels containing N-vinyl-2-pyrrolidone (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 321-330 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymer-water interaction parameters, sequence length distributions and contents of total, freezing and non-freezing water have been discussed for a family of hydrogels. The xerogel precursors contained N-vinyl-2-pyrrolidone (VP) with several co-monomers of different levels of hydrophobicity present in the xerogel over a wide range of composition. Common trends in the behaviour of these systems have been noted and rationalised. In particular the findings indicate that (i) in the poly-VP hydrogel ther are ca. 8-10 molecules of non-freezing water per VP unit and (ii) in the copolymeric hydrogels the maximum occurring in the variation of mole fraction of VP versus mole fraction of water is due substantially to the sharp increase in uptake of freezing (or bulk) water by copolymers rich in VP.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910206
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of crosslinker on properties of copolymeric N-vinyl-2-pyrrolidone/methyl methacrylate hydrogels and organogels (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 331-343 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The γ-ray initiated copolymerisation of N-vinyl-2-pyrrolidone with methyl methacrylate in the presence of crosslinker has been effected to high conversion. At two fixed compositions of the principal monomers, the inclusion of different concentrations of the tetrafunctional crosslinkers ethylene dimethacrylate and a low molar mass poly(ethylene glycol) dimethacrylate produced crosslinked xerogels, which were subsequently swollen in water and 1,4-dioxane to yield hydrogels and organogels, respectively. These gels were characterised by determinations of sol fraction, equilibrium solvent content and uniaxial compression stress/strain measurements. Differences among the swelling and mechanical properties according to the nature and concentration of crosslinking agent and according to the nature of the swelling medium are noted and discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910207
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  • 10
    Electronic Resource
    Electronic Resource
    Atom transfer radical copolymerization kinetics (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 371-375 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Starting from the basic radical mechanism of atom transfer radical polymerization (ATRP), simple expressions are derived for the description of atom transfer radical copolymerization kinetics. It is shown that kinetic parameters are interchangeable between atom transfer and conventional free-radical copolymerization, which is important for two reasons. Firstly, it enables the prediction of the average equilibrium constant (and hence average rate of polymerization) in an ATRP system with two monomers if the corresponding conventional kinetic parameters are known. Secondly, it enables the determination of the relative fractions of propagating radicals by a detailed ATRP study.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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