摘要:

AbstractThe possible cross reactions indicated by solid‐state NMR between cyanate functionalized resin and epoxy functionalized resin have been investigated by using both natural abundance and labeled monofunctional model compounds. These soluble products were isolated and purified by silica gel adsorption chromatography and gel permeation chromatography. They were fully characterized by high resolution1H‐,13C‐,15N‐NMR spectroscopy and by mass spectrometry. The major cross‐reaction product is a racemic mixture of enantiomers, which contain an oxazolidinone ring formed by one cyanate molecule and two epoxy molecules. However, epoxy consumption lags cyanate consumption in the overall reaction as triazine formation from the cyanate is much faster than the two competing reactions, the cross reaction between cyanate and epoxy, and the self‐polymerization of epoxy, under the conditions investigated. The cross reaction between cyanate and epoxy is limited. Approximately 12% of cross reaction between cyanate and epoxy was found in the overall reaction. In addition to the cross reactions of epoxy and cyanate, the reactions of epoxy and the carbamate, which is the major side product for the curing reaction of cyanate resin in solution, have also been investigated, and the mechanism of these reactions discussed. From the reactions of epoxy and carbamate, several products related to cross reaction between epoxy and cyanate have been isolated and identified. It is suggested that the reaction of epoxy and carbamate is one of the pathways in the overall cross reaction between epoxy and cranate resins. Finally, the mechanism of the overall cross‐curing reaction between the diepoxy and dicyanate mixed resins is discussed. © 1994 John W

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321201

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe course of composition drift in copolymerization reactions is determined by reactivity ratios of the contributing monomers. Since polymer properties are directly correlated with the resulting chemical composition distribution, reactivity ratios are of paramount importance. Furthermore, obtaining correct reactivity ratios is a prerequisite for good model predictions. For vinyl acetate (VAc), vinyl 2,2‐dimethyl‐propanoate also known as vinyl pivalate (VPV), and vinyl 2‐ethylhexanoate (V2EH), the reactivity ratios with methyl acrylate (MA) have been determined by means of low conversion bulk polymerization. The mol fraction of MA in the resulting copolymer was determined by1H‐NMR. Nonlinear optimization on the thus‐obtained monomer feed–copolymer composition data resulted in the following sets of reactivity ratios:rMA= 6.9 ± 1.4 andrVAc= 0.013 ± 0.02;rMA= 5.5 ± 1.2 andrVPV= 0.017 ± 0.035;rMA= 6.9 ± 2.7 andrV2EH= 0.093 ± 0.23. As a result of the similar and overlapping reactivity data of the three methyl acrylate–vinyl ester monomer systems, for practical puposes these data can be described with one set of reactivity data. Nonlinear optimization of all monomer feed–copolymer composition data together resulted inrMA= 6.1 ± 0.6 andrVEst= 0.0087 ± 0.023. © 1

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321202

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractEmulsion polymerization of tetrafluoroethylene and propylene with ammonium perfluorooctanoate, initiated by a redox system containingtert‐butylperbenzoate (TBPB) was carried out. The effect of the components of the redox system Is (TBPB, FeSO4.7H2O, ethylenediamine tetraacetic acid (EDTA), and CH2(OH)SO2Na.2H2O) on the polymerization rate (R) and molecular weight ($\[ \bar M_n \] $) was studied. Among redox system components, Fe2+concentration exerts the most significant effect (by power of 0.54) on the polymerization rate. It was found that R ∝ [Is]0.2–0.54and Mn∝ [Is]0.0–0.1and polymerization reaction scheme was suggested for the action of the initiating system. The influence of the copolymerization conditions (pressure, temperature, stirring speed, and pH) is also discussed. The apparent activation energy of the reaction was found to be 46.0 kJ/mol. © 1994 John Wiley

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321203

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractEmulsion copolymerization of tetrafluoroethylene (TFE) and propylene (P) initiated by trilon‐rongalite catalytic system containingtert‐C4H9OH, initial monomer mixture, emulsifier (C7F15COONH4) concentration, and monomer mixture/water ratio on the polymerization rate (R) and molecular weight (M̄n) was investigated. BothRand M̄nincreased considerably with TFE content in monomer mixture up to 75 mol %. Alternating rubber‐like copolymers in a wide range of initial monomer mixture (from 55–85 mol %) were obtained. The reactivity ratio was found to berTFE= 0.005 ± 0.04 andrp= 0.17 ± 0.07. Above the critical miscelle concentration, the effects of the initiating systemIsand emulsifierCsonRand M̄nwere found to obey the following relations:\documentclass{article}\pagestyle{empty}\begin{document}$$ {R \propto [Is]^{0.54} \times [Cs]^{0.42} }\quad {{\rm and}}\quad {\bar M}_n \propto [Is]^{ - 0.1} \times [Cs]^{0.1} ,$$\end{document}according to which emulsion copolymerization proceeds by theIcase of Smith‐Ewart theory. Polymerization mechanism of the reaction studied was suggested. The copolymerization is mainly terminated by degradative chain transfer of the propagating radicals to propylene. © 1994 John

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321204

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe photodissociation of severalN,N‐diethyldithiocarbamate derivatives (RDC), i.e., benzyl, 1‐phenylethyl, 2‐phenylethyl,n‐butyl,sec‐, andtert‐butylN,N‐diethyldithiocarbamates, was investigated by the spin trapping technique to elucidate the polymerization mechanism of styrene (St) with RDC as iniferters. The scission of RDC occured at two different CS bonds depending on the structure of the alkyl groups of RDC and the cleavage manner was dominated by both resonance and steric effects. It has been confirmed that RDC generating anN,N‐diethyldithiocarbamyl radical acts as an effective iniferter and induces the living radical polymerization of St in homogeneous system. The polymerizations of St with tetraethylthiuram disulfide andp‐xylylene bis(N,N‐diethyldithiocarbamate) were also discussed on the basis of the results of the spin trapping for RDC as the model compounds of the poly(St) chain ends. © 199

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321205

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractN‐vinyl carbazole (VCZ) was grafted on cellulose acetate film using simultaneous cobalt‐60‐γ ray irradiation grafting technique. Absorption, excitation, and emission spectral studies on the grafted film were carried out to ascertain the grafting of VCZ on the polymer matrix. Laser‐flash photolysis studies with the solution of grafted film indicate the opening of the double bond of VCZ, which leads to the grafting. On the basis of the observed results, the mechanism of grafting in the system was proposed. © 1994 John Wiley&

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321206

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA partial hydrolysis of amylose followed by the addition of iodine provides a spectrum almost identical to that of the amylopectin–iodine (API) complex suggesting the involvement of smaller “amylose‐like” units in the API complex. Our theoretical studies on different polyiodine and polyiodide species suggest that a nearly linear I4unit stabilized within the cavity of a small “amylose‐like” helix is responsible for the characteristic API spectrum. Since there are 2.75 anhydroglucose residues (AGU) for every iodine atom in the amylose–iodine (AI) complex and a structural similarity exists between the API and the AI (amylose–iodine) complexes, we identify (C6H10O5)11I4to be the chromophore in the API complex. © 1994 Jo

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321207

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe iodine binding capacity (IBC) of amylopectin (AP, from potatoes) is determined to be around 0.38% (w/w) of the total AP in the solution. The mass of iodine bound comprises about 13.6% of the mass of AP involved with the complex, suggesting that with every four iodine atoms bound there are 23 anhydroglucose residues (AGU). Since our previous study indicates that four iodine atoms within the helix of 11 AGUs form a chromophore unit in the API complex, only 48% of the AGUs (11 out of 23) in the AP molecule are directly involved with the iodine. The heat of reaction for the API complex formation is determined to be around −47 kJ/mol of I–I units bound and is significantly lower in magnitude than that of the amylose‐iodine (AI) complex [Biopolymers,31, 57 (1991)]. A possible mechanism has been proposed for the formation of AI and API complexes with fixed compositions. © 1994 John Wiley&Son

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321208

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPlasma polymerized methyl methacrylate (PPMMA) films have been synthesised on silicon substrates in RF glow discharge using oxygen plasma. The electron beam delineation sensitivity of the PPMMA films has been studied systematically by varying oxygen and monomer flow rates. X‐ray photoelectron spectroscopy (XPS) analysis clearly illustrates how C/O ratio in the films determines the properties of PPMMA films as electron beam resist. © 1994 John Wiley&Sons, I

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321209

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractVarious bicyclic amide acetals were synthesized from the cycloaddition reactions of 2‐substituted‐2‐oxazolines with styrene oxide. Ring‐opening polymerization of the bicyclic amide acetals occurred upon heating in the presence of methyl tosylate. Characterization of the bicyclic amide acetals and their polymers was accomplished by NMR and elemental analysis. Vapor pressure osmometry showed the highest polymer molecular weight was only 2,400. The mechanisms for cycloaddition and polymerization are discussed. © 1994 John Wiley&S

ISSN:0887-624X    

DOI:10.1002/pola.1994.080321210

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY