Méthodes chimiques d'analyse des polyacroléines linéaires

Linear polyacroleins prepared by anionic polymerization give the structural repeat units of the types \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--}[{\rm CH}\left( {{\rm CHO}} \right)\hbox{--} {\rm CH}_{\rm 2} {\rm \rlap{--} ], \rlap{--} [CH}_{\rm 2} \hbox{--} {\rm CH}\left( {{\rm CHO}} \right)\rlap{--} ], $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}\left( {{\rm CH}\hbox {\rm CH}_2 } \right)\hbox{\rm O\rlap{--} ]} $\end{document} without any cyclization. Analysis of these polymers by several methods reveal the nature and amount of each structural species, and an estimation of their distribution along the polymeric chain.     

Structural study of alternating copolymerization of aziridines with cyclic imide

The structures of copolymers of aziridines with cyclic imides were determined by means of infrared spectrometry, paper electrophoresis of the hydrolyzate, and NMR spectrometry. The structure of the repeating unit in the copolymer of ethylenimine with succinimide was \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} ({\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CONH}\rlap{--} ) $\end{document}. The endgroups of the copolymer were N-acylethylenimine ring, N-substituted succinimide ring, and primary amide group. The copolymer of ethylenimine with N-ethylsuccinimide had the repeating unit of \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups of N-acylethylenimine and N-substituted succinimide ring. N-Ethylethylenimine did not copolymerize with succinimide, but in the presence of water, the reaction occurred to give an amorphous polymer. This copolymer had the repeating unit \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_2 {\rm CH}_2 {\rm NHCOCH}_2 {\rm CH}_2 {\rm CON}({\rm C}_2 {\rm H}_5 )\rlap{--} ] $\end{document} and the endgroups were N-substituted succinimide ring and amine group but not N-acylethylenimine ring. On the basis of this structural information, the initiation reaction was discussed.     

Polymerization of (o-methylphenyl)acetylene and polymer characterization

(o-Methylphenyl)acetylene polymerized with high yields in the presence of W and Mo catalysts. W catalysts were more active than the corresponding Mo catalysts. The weight-average molecular weight of the polymer formed with W(CO)₆–CCl₄–hv reached 8 × 10⁵, being higher than the maximum value (ca. 2 × 10⁵) for poly(phenylacetylene). The polymer had the structure $\rlap{--} [{\rm CH} \hbox{=\hskip-1pt=} {\rm C}(o - {\rm CH}_3 {\rm C}_6 {\rm H}_4 )\rlap{--} ]_n $. The stereochemical structure of the main chain could be determined by ¹³C-NMR; the cis content varied in a range of 41–61% depending on the polymerization conditions. The present polymer was thermally more stable than poly(phenylacetylene) according to thermogravimetric analysis. Interestingly, this polymer possessed deeper color than poly(phenylacetylene), and showed a fairly strong absorption in the visible region.     

Polycarboxyhydrazides with ferrocenylene groups in the main chain

Polycarboxyhydrazides essentially of the type \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm C}_{10} {\rm H}_8 {\rm Fe}\hbox{---}{\rm CONHNHCO}\rlap{--}]_n $\end{document} are synthesized by low-temperature solution condensation of 1,1′-di(chlorocarbonyl) ferrocene with hydrazine or 1, 1′-ferrocenedicarboxyhydrazide and hexamethylphosphoramide as solvent. In an analogous manner the polycondensation of 1, 1′-di(chlorocarbonyl)ferrocene with oxalyldihydrazide leads to polyhydrazides essentially possessing the structure \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm C}_{10} {\rm H}_8 {\rm Fe}\hbox{---}{\rm CONHNHCO}\hbox{---}{\rm CONHNHCO}\rlap{--}]_n $\end{document}. Both polymer types exhibit inherent viscosities (0.08–0.19 dl./g.) considerably lower than reported for analogous aliphatic or benzene-aromatic polyhydrazides. This behavior points to premature chain termination via heterobridging imide groups as a result of the welldocumented tendency of appropriately substituted ferrocene compounds to undergo intramolecular cyclization. In addition, elemental analytical and spectroscopic evidence, coupled with the failure of both polymer types to undergo cyclodehydration to the corresponding 1,3,4-oxadiazole polymers upon heat treatment, suggests some structural irregularities in the aliphatic connecting segments arising from ferrocenoylation of secondary amino groups with resultant branching. With the polyhydrazide prepared from 1, 1′-di(chlorocarbonyl)ferrocene and 1, 1′-ferrocenedicarboxyhydrazide it is shown spectroscopically that treatment with alkali results in conversation of the nonconjugated hydrazide structure of the connecting segments into the polyconjugated tautomeric enol form comprising azine groups.     

Thermal analysis of polysiloxanes. II. Thermal vacuum degradation of polysiloxanes with different substituents on silicon and in the main siloxane chain

Thermogravimetric (TG) investigations of various substituted polysiloxanes of the type \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm R}_1 {\rm R}_2 {\rm SiO\rlap{--} )}_n $\end{document} have been carried out in vacuo and the activation energies for the depolymerization processes calculated from the resulting thermograms. (R₁ and R₂ are methyl, ethyl, n-propyl, trifluoropropyl, or phenyl.) It is postulated that the activation energy is mainly a function of the inductive effect of the substituent group and that electron-withdrawing groups attached to silicon increase the activation energy, whereas electron-donating groups decrease it. A linear relation is found between the Taft constant σ^* for the substituent on silicon and the calculated activation energy for depolymerization. Product analysis results from isothermal degradations indicate that the degradation mechanism in a silmethylene siloxane polymer and a silethylene-siloxane polymer is very similar to that in polydimethylsiloxanes (PDMS). For the \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm R}_1 {\rm R}_2 {\rm SiO\rlap{--} )}_n $\end{document} polymers, the amount of cyclotrisiloxane in the degradation products increases with the size of the substituent on silicon, and it is postulated that the rate of depolymerization is mainly influenced by short-range steric interactions between the substituents on the silicon atoms of the siloxane chain.     

Efficient, “one-pot” synthesis of silylene–acetylene and disilylene–acetylene preceramic polymers from trichloroethylene

An extremely efficient process has been developed for the synthesis of linear silylene-acetylene and disilylene-acetylene polymers. Trichloroethylene is quantitatively converted by n-butyllithium to dilithioacetylene. Quenching with dialkyl-or diaryldichlorosilanes affords high yields of the polymers, $ \rlap{--} [{\rm SiR}_{\rm 2} \hbox{---} {\rm C} \equiv {\rm C\rlap{--} ]}_n ,{\rm and }\rlap{--} [{\rm SiMe}_{\rm 2} {\rm SiMe}_{\rm 2} - {\rm C} \equiv {\rm C\rlap{--} ]}_n $ if ClMe₂SiSiMe₂Cl is employed. Molecular weights are much higher with this route than when acetylene is used as the dilithio- or dimagnesium acetylide precursor. Some of these polymers can be pulled into continuous fibers, and all can be cast into coherent films and thermally converted into silicon carbide.     

Alternating copolymerization of dienes with α-olefins

Alternating copolymerization of butadiene with several α-olefins and of isoprene with propylene were investigated by using a mixture of VO(Acac)₂, Et₃Al, and Et₂AlCl as catalyst. The alternating copolymerization ability of the olefins decreases in the order, propylene > 1-butene > 4-methyl-1-pentene > 3-methyl-1-butene. The study on the sequence of the copolymer of isoprene with propylene by ozonolysis reveals that the polymer chain is reasonably expressed by the sequence \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} [{\rm CH}_{\rm 2} \hbox{--} {\rm CH} \hbox{=\hskip-1pt=} {\rm C(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \hbox{--} {\rm CH(CH}_{\rm 3}) \hbox{--} {\rm CH}_{\rm 2} \rlap{--}]_n $\end{document}. NMR and infrared spectra indicate that the chain is terminated with propylene unit, forming a structure of ?C(CH₃)? CH₂? C(CH₃)?CH₂ involving a vinylene group.     

Influence of addition of ethylene on the γ-ray-induced alternating copolymerization of ethylenimine and carbon monoxide

The influence of the addition of ethylene on the γ-ray-induced alternating copolymerization of ethylenimine and carbon monoxide was investigated. A mixture of ethylenimine, carbon monoxide, and ethylene was irradiated to produce a polymer containing these monomeric units. The infrared spectrum of the copolymer showed the characteristic absorption peaks of the secondary amide and ketone bond and was different from that of the reaction product of polyketone with ethylenimine and that of the γ-ray irradiation product of ethylene and poly-ß-alanine. The x-ray diffraction diagram of the copolymer was different from those of poly-ß-alanine and polyketone and exhibited an amorphous structure. Paper chromatographic analysis showed that the hydrolysis product of the copolymer contained ß-alanine and δ-aminovaleric acid. These results indicate that terpolymerization of ethylenimine, carbon monoxide, and ethylene took place under γ-ray irradiation and gave an amorphous polymer containing the units \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{} ({\rm CH}_{\rm 2} {\rm CH}_{\rm 2} {\rm NHCO}\rlap{}),\rlap{} ({\rm CH}_{\rm 2} {\rm CH}_{\rm 2} {\rm CO}\rlap{}),{\rm and}\rlap{} ({\rm CH}_{\rm 2} {\rm CH}_{\rm 2} {\rm CH}_{\rm 2} {\rm CH}_{\rm 2} {\rm NHCO}\rlap{}) $\end{document}     

Living reversible anonic polymerization of N,N-diethylamine-1,3,2-dioxaphosphorinan

Polymerization of the cyclic amide of P^III is described for the first time. The N,N-diethylamine-1,3,2-dioxaphosphorinan was shown to give living reversible polymerization with anionic initiators. Lithium and sodium derivatives were found to be inactive. ¹H-, ¹³C-, and ³¹P-NMR indicated that the polymer strictly reflects the monomer structure and is formed without any isomerization, the polymer chain being $\rlap{--} ({\rm OP}\left( {{\rm NR}_{\rm 2} } \right){\rm O(CH}_{\rm 2} \rlap{--} )_3 )_n $. Initiation involves attack of the anion on the P atom. From the dependence of the equilibrium monomer concentration on temeprature ΔH_1s = 1.5 ± 0.2 kcal·mol^?1 and ΔS_1s = 4.6 ± 0.6 cal·mol^?1·°K^?1.     

Aspects of the synthesis and the properties of linear poly-2,5-dimethylbenzylenes

Polydimethylbenzylenes, \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} [C_6 H_2 (CH_3 )_2 CH_2 \rlap{--} ]_n$\end{document}, have been obtained by polycondensation of the monochloromethyl, acetoxymethyl, and methoxymethyl derivatives of p-xylene, via an acid-catalyzed reaction in anhydrous acetic acid and in 1-nitropropane. In the highly ionizing solvent acetic acid, because of ionic depolymerization, chain growth takes the form of an equilibrating polycondensation, of a maximum number-average molecular weight of 2200. In the noninteracting solvent 1-nitropropane, the molecular weight distribution is more random, and soluble polymers of number-average molecular weight up to 3900 are formed. The polycondensation reaction in 1-nitropropane is also initiated by perchlorate salts, in support of the suggestion of a “hot carbonium ion” propagation mechanism. The results are explained by a cataionic polycondensation reaction, yielding crystalline “living polymers” of high structural purity.     

Block copolymers derived from azobiscyanopentanoic acid. VI. Synthesis of a polyethyleneglycol–polystyrene block copolymer

Polycondensations were carried out between azobiscyanopentanoly chloride (ACPC) and polyethyleneglycols (PEG) having average molecular weight of 600, 2000, 8400, and 21,500, resulting in the chain extended PEG of several times the original polymer chain length and containing scissile ? N?N? units of azobiscyanopentanoic acid (ACPA). The poly(polyethyleneglycol-azobiscyanopentanoate), designated as \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--} (PEG\rlap{--} )_n^*$\end{document} were thermally decomposed in the presence of styrene (St) to obtain PEG–PSt block copolymers. The amount of St consumed was proportional to [? N?N? ]^0.5 and [St]^1.2, whereas the chain length of the PSt segment was proportional to [? N? N? ]^?0.5 and [St]^0.8.     

Applications of NMR spectroscopy of chiral association complexes 5. Stereodynamics and diastereotopism in chiral 1,3-dienes \documentclass{article}\pagestyle{empty}\begin{document}${\rm HOCMe}_{\rm 2} \rlap{--} ({\rm CCl =\!= CCl\rlap{--})}_{\rm 2} {\rm X}$\end{document}

The barriers to partial rotation around the central single bond in chiral dienes \documentclass{article}\pagestyle{empty}\begin{document}${\rm HOCMe}_{\rm 2} \rlap{--} ({\rm CCl =\!= CCl\rlap{--})}_{\rm 2} {\rm X}$\end{document} have been determined by coalescence of either ¹H NMR signals (X = CH₂OCH₃) or ¹³C NMR signals (X = H). In the presence of the optically active shift reagent (+) ? Eu(hfbc)₃ all ¹H signals were split at temperatures where the interconversion of enantiomers is slow. The temperature dependence of these spectra also yielded free activation enthalpies for the enantiomerizations which were in agreement with the ones obtained without Eu(hfbc)₃. The assignment of the four methyl resonances appearing in the presence of (+) ? Eu(hfbc)₃ at low temperature was possible by gradually increasing the rate of enantiomerization or gradually replacing the optically active auxiliary compound by the racemic one.     

Synthesis of polyamides by the polyaddition of bissuccinimides with diamines

Polyamides which contain succinamide units, ? NHCO? (CH₂)₂? CONH? were prepared by the ring-opening polyaddition of bissuccinimides with diamines at 200°C. in bulk. Nylon 24 and nylon 64 were prepared by the reaction of N,N′-ethylenedisuccinimide with ethylenediamine and of N,N′-hexamethylenedisuccinimide with hexamethylenediamine, respectively. It was suggested that the transamidation reaction by aminolysis influenced the detailed structures of the polymers prepared from N,N′-ethylenedisuccinimide and hexamethylenediamine and from N,N′-hexamethylenedisuccinimide and ethylenediamine. The detailed structures of the polymers are discussed on the basis of their melting points and x-ray diagrams. It is concluded that the polymers contain a crystalline portion of \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--}[{\rm NH \hbox{--} (CH}_2 {\rm)}_{\rm 2} {\rm \hbox{--} NHCO \hbox{--}}({\rm CH}_2)_2 {\rm \hbox{--} CONH \hbox{--}}({\rm CH}_2)_6 {\rm \hbox{--} NHCO \hbox{--}}({\rm CH}_2)_2 {\rm \hbox{--} CO\rlap{---}]} $\end{document} sequences.     

Reactions of/n\pi ^{\rlap{--} x} / and/\pi \pi ^{\rlap{--} x} / states of triplet acetophenone with hydroperoxide moleculesstates of triplet acetophenone with hydroperoxide molecules

The photochemical interaction of triplet acetophenone /^TRO/ with α-phenyl ethyl hydroperoxide /HROOH/ has been studied in CCl₄ and CH₃CN. In CCl₄ only the \(/n\pi /^{\rlap{--} x}\) state of^TRO is active abstracting hydrogen from HROOH molecules. In CH₃CN both hydrogen abstraction and homolysis of HROOH take place, that is both \(/n\pi /^{\rlap{--} x}\) and \(/\pi \pi /^{\rlap{--} x}\) states of triplet RO play active role.     

A phase polymorphism N?SAd?I in liquid-crystalline polymethacrylates with 4′-trifluoromethoxyazobenzene mesogenic side groups

The mesophase behaviour of liquid-crystalline polymethacrylates with 4′-trifluoromethoxyazobenzene mesogens and alkylene spacers $ \left( {\rlap{--} ({\rm CH}_{\rm 2} \rlap{--} )_n ,n = 2 - 6} \right) $ in the side chains was investigated and compared with that of the corresponding non-fluorinated polymers. The fluorinated polymers with spacer lengths n = 5 and 6 are the first side-group liquid-crystalline polymethacrylates showing a nematic phase below a smectic A phase.     

Stereochemical regulation of polypropylenes prepared with various Ziegler-Natta catalysts

The 220-MHz proton magnetic resonance and infrared spectra of stereoregular polypropylenes polymerized with a number of Ziegler-Natta catalysts and isotactic polymers of low molecular weight obtained by thermal degradation of a highly isotactic polypropylene were measured in an attempt to obtain some information on the local regularity. The fraction of thermally degraded polymer soluble in diethyl ether shows stereorandomness (tactie sequence length is quite short), and the portion soluble in n-pentane has stereoblock character. The results so obtained provide strong evidence that racemic dyads of whole polymer consist of two models of racemic dyad isolated and racemic dyads in groups. The polymers prepared with vanadium catalyst systems show stereorandom character and these polymers have \documentclass{article}\pagestyle{empty}\begin{document}$\hbox{-\hskip-1pt-}\hskip-4pt({\rm CH}_2 \rlap{--} )$\end{document} groups formed by two propylene units in a tail-to-tail linkage. Syndiotactic polypropylene has head-to-head and tail-to-tail arrangements of two propylene units and this is the origin of randomness of syndiotacticity.     

Sliding in polytetrafluoroethylene crystals

Stress–strain relationships are calculated for three models of the deformation of monocrystalline polytetrafluoroethylene, \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm CF}_{\rm 2} \rlap{--} )_n $\end{document}. The physical models comprise either sliding one molecule or one plane of molecules parallel to the molecular chain axis past its stationary neighbors. The potential energy is calculated for each stage of deformation by semiempirical methods by use of 6-exp and dipole–dipole interactions. Application of Eyring's activated complex theory leads to stress–strain relationships. These are compared with results of friction measurements on PTFE.     

Surface Fluorination of Carboxylated Nitrile Butadiene Rubber: An XPS Study

Because of their exceptional reactivity, fluorine and fluorinated gases are of primary importance for the modification of the surface properties of materials. This study is devoted to surface treatment of thin nitrile gloves, made of carboxylated nitrile butadiene rubber latex, using either direct fluorination (10% F₂gas diluted in N₂) or plasma-enhanced fluorination in radio-frequency cold plasmas using fluorinated gases (CF₄, CHF₃). Mechanisms of fluorination of these co-elastomers have been proposed on the basis of the assignment of the different components of the XPS spectra. Several mechanisms have been observed depending on the fluorination conditions. Although the modification of nitrile gloves is already effective for fluorination reactions at room temperature, an important activation is observed for experiments carried out at 90°C. When the treatments are carried out at room temperature, a gradual fluorination occurs: in the case of 10% diluted F₂ gas, monofluorinated C—F groups are the species most found at the surface and perfluoro groups CF _n are present in lower amount. An addition reaction takes place at the CH=CH double bonds of the polybutadiene entities, leading to CHF=CHF units. Whatever the fluorination method, thermal activation yields a more massive fluorination of the surface that finally leads to perfluorinated CF₂ groups and terminal —CF₃ groups.     

Effect of polymer crystallinity on the wetting properties of certain fluoroalkyl acrylates

The wetting properties of a series of polyacrylates containing the fluoroalkyl group \documentclass{article}\pagestyle{empty}\begin{document}$ [\rlap{--} ({\rm CF}_{\rm 2} \rlap{--} )_2 {\rm CF}_2 {\rm H}\ $\end{document} have been studied. Where n is 7 and 9, the polyacrylates are highly crystalline at room temperature. Since the polymers were prepared under atactic free-radical conditions and the polyacrylates with shorter alkyl groups (where n is 3 or 5) were not crystalline at room temperature, the crystallinity is presumed to occur as a result of side-chain packing and not involve the backbone. The polymers become more wet-table (higher γ_c) as polymer crystallinity was reduced by quenching or heating past T_m. Correlations have been made between the work of Zisman and co-workers on the wetting properties of various fluorinated acid monolayers and the wetting properties of these fluoroalkyl acrylates. The results obtained in this study concerning the influence of polymer crystallinity on surface wetting are discussed in relation to the findings of Schonhorn and Ryan on the wettability of polyethylene single crystal aggregates.     

Synthesis and liquid crystalline properties of thermotropic homo- and copolycarbonates

Nondirect-type thermotropic homo- and copolycarbonates which have flexible spacers between mesogens and carbonate linkages (-mesogenic unit-flexible spacer-carbonate link-flexible spacer-) were derived from dihydroxyalkyleneoxy derivatives containing biphenyl, i.e., 4,4′-bis (ω-hydroxyalkyleneoxy)biphenyl (Ia and Ib), as mesogens and the structure-liquid crystallinity relationships were evaluated by thermal analysis and with polarizing microscope. Homopolycarbonates with high molecular weight were prepared from (Ia) and (Ib), and alkylene diphenyl dicarbonates (II) by melt polycondensation. The polymers form mesomorphic phases and exhibit linear decrease of phase-transition temperatures with increment of alkylene spacer lengths without displaying odd-even number fluctuations. They show lower phase-transition temperatures and narrower mesomorphic temperature ranges than analogous direct-type (-mesogenic unit-functional group-flexible spacer-) biphenyl-containing polycarbonates \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm OMOC}({\rm O}){\rm O}({\rm CH}_2)_m {\rm OC}({\rm O})\rlap{--})_x $\end{document} and polyesters \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm OMOC}({\rm O})({\rm CH}_2)_m {\rm C}({\rm O})\rlap{--})_x $\end{document}, but have wider temperature ranges than nondirect-type (-mesogenic unit-flexible spacer-functional group-flexible spacer-) biphenyl-containing polyesters \documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm O}({\rm CH}_2)_n {\rm OMO}({\rm CH}_2)_n {\rm OC}({\rm O})({\rm CH}_2)_m {\rm C}({\rm O})\rlap{--})_x $\end{document}. These results indicate that by the incorporation of alkylene segments between mesogens and carbonate linkages the polymers having reasonable phase-transition temperatures and wider mesophasic temperature ranges can be obtained. Copolycarbonates were prepared from mixtures of (Ib) and 1,4-bis(2-hydroxyethyleneoxy)benzene (IV), nonmesogenic moiety, taken in definite molar ratio in feed and (II) (m = 2 and 4). These copolymers except polymers having only nonmesogenic moiety show liquid crystalline mesophases and have wider phase-transition temperature ranges than the homopolymers. Maximum temperature ranges are observed in the copolymers of composition ratio of 1 : 1. Stable mesophases can be obtained over the entire range of compositions, even though the copolymers contain nonmesogenic units in the backbones.