摘要:

AbstractHydroxymethylation of melamine with formaldehyde to formN‐(hydroxymethyl)melamine (2,4‐diamino‐6‐hydroxymethylamino‐1,3,5‐triazine) was investigated kinetically by the use of hydrogen phosphate/phosphate buffers in aqueous media at pH 11 − 12. This reaction was found to follow a general base catalysis which results from the kinetic investigation, showing that the reaction takes place by a concerted mechanism involving base, melamine, and formaldehyde. This mechanism differs from that of the base catalyzed hydroxymethylation of phenol or benzamide with formaldehyde, because the acidic phenol and benzamide easily form their conjugate bases by addition of the basic catalyst in a preceding equ

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830411

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe absorption band at 1378 cm−1was used for the quantitative determination of branching in polyethylene. Using various models with different alkyl groups (12‐alkyltriacosanes, 11,20‐dialkyltriacontances, alkylcyclohexanes, homopolymers), new absorption coefficients, depending on their branching, were obtained. The degrees of branching of a series of copolymers deriving from α‐olefins (15 compounds) determined by infrared spectroscopy with the new coefficients and by13C NMR spectroscopy were

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830412

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractSemiflexible mesophasic polymers of the general formula\documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm OOC(CH}_{\rm 2} {\rm )}_{n - 2} - {\rm COO} - {\rm R}^1 \rlap{--} ]_{\rm X} ,n = 9,11,13,\rlap{--} [{\rm OOC(CH}_{\rm 2} )_{n - 2} - {\rm COO} - {\rm R}^2 \rlap{--} ]_{\rm X} ,n = 9,11,13,14, $\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm OOCO} - {\rm (CH}_{\rm 2} {\rm )}_{n - 4} - {\rm OCOO} - {\rm R}^2 \rlap{--} ]_{\rm X} ,n = 9,11,13, $\end{document}where\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}^{\rm 1} = - {\rm C}_{\rm 6} {\rm H}_{\rm 5} - {\rm C}({\rm CH}_3 ) = {\rm CH} - {\rm C}_6 {\rm H}_5 - $\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}^{\rm 2} = {\rm C}_{\rm 6} {\rm H}_{\rm 5} - {\rm C}({\rm CH}_3 ) = {\rm N} - {\rm N} = ({\rm CH}_3 ){\rm C} - {\rm C}_6 {\rm H}_5 - $\end{document}are prepared and their solid and liquid crystalline behaviour examined and compared to that of the corresponding homologues withneven. Evidence is given of relevant odd‐even effects in the thermodynamic parameters of the clearing transition. The conclusion is drawn in favour of an anisotropic structuration also of the flexible parts of the polymer chain in the liquid crystal phas

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830413

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPolymerisation of methyl acrylate (MA) initiated by O2‐ascorbic acid (AA)‐Cu2+system was studied in aqueous medium at 40°C. The rate of polymerisationRp, was found to increase, remain constant, and then decrease with increasing [Cu2+].Rpwas found to depend on [Cu2+]0,6, [AA]0, [O2]0,6, and [MA]1,3in the increasing region, on [Cu2+]0, [AA]0, [O2]0,6, and [MA]1,6in the constant region and on [Cu2+]−0,9, [AA]0, [O2]0,7, and [MA]2,0in the decreasing region. Rate laws were derived assuming a plausible reaction mechanism for the different regions.Rpincreased with ionic strength and decreased with [H2SO4,]. An initial increase, then steady state followed by a decrease in rate with temperature was noticed in the range 25 − 55°C.kp/kt1/2values were calculated and compared with literature values. Chain lengths were determined viscom

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830414

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

Abstract2,6‐Dimethoxyphenol was polymerized using Ag2O‐triethylamine complex as catalyst and a study made of the effect of the catalyst‐monomer ratio on the yield, molar mass and polydispersity of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene). The glass transition temperaturesTgwere measured with a computerized differential scanning calorimeter. The effect of the molar mass onTgof poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene) is discussed. The equation,Tg=Tg, ∞−K/M v0,64, describes well the dependence ofTgon the viscosity‐average molar massMvfrom 1900 to 176000 g/mol. Some poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) sampl

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830415

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe heat capacities of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene) were measured from 160 to 480 K using a differential scanning calorimeter (DSC) interfaced to a computer for data collection and processing. The values for the heat capacities between 160 and 420 K were tabulated. Below 280 K they depend only slightly on the molar mass, whereas above 280 K the conformational changes of the end groups have a noticeable effect. Wunderlich's addition scheme for the calculation of heat capacities from the empirical group contributions gives results that agree within ± 1% with the experimental data. The heat capacity jump ΔCpatTgdepends inversely on the molar mass. Wunderlich's “bead” model for ΔCpvalues is discussed for poly(oxy‐2,6‐disubstitu

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830416

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe thermal expansion coefficient of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene), PPOO, was measured from 150 to 500 K, using a thermomechanical analyzer connected to a computer for the data handling. Poly(oxy‐2,6‐dimethyl‐1,4‐phenylene), PPO, and some brominated poly(oxy‐2,6‐disubstituted‐1,4‐phenylene)s were studied as reference materials. The apparent glass transition temperatures of the high molar mass polymers were 456 K for PPOO and 487 K for PPO, and the changes in cubic thermal expansion coefficients atTgwere 6,01 · 10−4K−1for PPOO and 4,23 · 10−4K−1for PPO. The activation of the β‐relaxation was found for PPOO at 260 K and attributed to the hindered torsional oscillations of the backbone phenylene groups. Another transition was found at 160 − 170 K and interpreted as the γ‐relaxation due to the oscillatory motion of the methoxy groups. Reasons for the differences in the thermal expansio

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830417

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe activation enthalpies for the structural relaxation of poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene) and poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) were determined by studying the dependence of the limiting fictive temperature on the cooling rate, using a differential scanning calorimeter (DSC) interfaced to a computer. The molar mass dependence of the activation enthalpies complied with the empirical equation, ΔH˙= ΔH ∞˙−A/M va, where ΔH ∞˙is the activation enthalpy of an infinite chain length polymer, Mvis the viscosity‐average molar mass,a= 0,64, andAis a constant that depends on the free volume of the chain ends of the polymers. The values of ΔH ∞˙are 433 kJ/mol for poly(oxy‐2,6‐dimethoxy‐1,4‐phenylene) and 44

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830418

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractRelations between molar massMand molar mass dependent propertiesEof polymers are mostly strictly valid only for monomolecular samples i:\documentclass{article}\pagestyle{empty}\begin{document}$ M_i = {\rm f (}E_i )\quad \quad \quad \quad \quad \quad (1{\rm a}) $\end{document}For polymolecular polymer samples thecorresponding averagesMavandEavmust be applied:\documentclass{article}\pagestyle{empty}\begin{document}$ M_{{\rm av}} = {\rm f (}E_{{\rm av}} )\quad \quad \quad \quad \quad \quad (1{\rm b}) $\end{document}Provided the kind of average (number‐, weight‐ or any general average) of e.g.Mavis known, the corresponding averageEavis given by. Eqs. (1a, b). This is demonstrated for the relationships of van't Hoff and Mark‐Houwink, frequently used for the determination of molar masses of polymers. It is also shown that the four different relations for the expansion factor α by Flory‐Stockmayer, Fixman, Ptitsyn, and by Yamakawa‐Tanaka can be applied topolymolecularpolymer samples (i.e. without fractionation), provided the corresponding averages[η]avandMavfrom the Mark‐Houwink relationship are taken for the evaluation of the para

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830419

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractN‐Methacryloyl‐N‐methylcrotonamide (MMCA) was prepared by the reaction of methacryloyl chloride withN‐methylcrotonamide. WhileN,N‐disubstituted methacrylamide and crotonamide, which can be considered as structual moieties of MMCA, do not homopolymerize, nevertheless MMCA yielded a homopolymer consisting of 5‐membered cyclic repeating units. MMCA was found to be more reactive than N‐propyldimethacrylamide in copolymerization with styrene and methyl methacrylate. Since the polymer radical adds to the methacrylamide moiety, the steric hindrance of a β‐methyl group in the crotonamide moiety must be less significant than that of the α‐methyl group of the methacrylamide moiety in the dimethacrylamide. The 5‐membered ring formation during the polymerization of MMCA was facilitated by the favorable conformation of the three carbon atoms concerned in the ring closure to achieve coplanarity, which is required for the fast 5‐membered ring closure. The coplanarity of the three carbon atoms and reluctance to homopolymerize of the reacting double bonds seem to be the minimum requirements for forming of a polymer consisting of solely 5‐member

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830420

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY