Comparative dielectric and thermotropic properties of liquid crystalline polyesters as a function of mesogen group and flexible thioether group length

Two polyesters containing rigid biphenyl and hydroquinone bisbenzoate groups and presenting flexible thioether moieties with different lengths (14 elements in the flexible group) have been carried out using a reaction of the Michaël type. The properties of these polyesters have been compared to those of polyesters of the same type presenting shorter flexible groups (11 elements). All these polymers present thermotropic properties: the biphenyl ones are smectic and the bisbenzoate ones are nematic. The biphenyl polyesters present two types of dielectric relaxations: α and β. The bisbenzoate ones show three relaxations, α and two β (β and β^′). The lengthening of the flexible group increases significantly the flexibility of the molecular chains.     

Glass fibre sizing effect on dynamic mechanical properties of cyanate ester composites I. Single frequency investigations

In order to investigate sizing effect in composite materials, we studied three types of composites, with different sizings. Dynamic mechanical analysis appeared to be a good way to characterize the α relaxation process of composites and their interphases. Results showed that α relaxation temperature shifted to higher temperatures for composites without sizing. Study of sizing extract/resin blend showed too that interphase was a mixture of polyvinyl acetate and cyanate resin. The results allow us to deduce that a plastification effect of resin by sizing could occur, with modification of crosslink density. Moreover, we can think that all resin is affected by sizing and the conversion rate in interphase is not total.     

Telomeres photoreticulables—2. Synthese de telomeres photoreticulables a partir des hydroxy-2-ethyl acrylate et methacrylate et des β-cinnamoyl oxy ethyl acrylate et methacrylate

Photocrosslinkable telomers based on cinnamoyl derivatives of polyacrylates and methacrylates can be prepared either by reaction of cinnamoyl chloride with telomers of hydroxy-2-ethyl acrylate and methacrylate, or by direct telomerisation of β-cinnamoylethyl acrylate and methacrylate. The first method gives products containing at least 70% of the theoretical maximum olefinic unsaturation but with low $\text{DP}$_n [1–20]; the second method gives telomers of high $\text{DP}$_n with the maximum number of cinnamoyl side-chains.     

Telomerisation par catalyse redox—II. Telomerisation du styrene,de l'acrylonitrile,et du monochlorotrifluoroethylene par des telogenes chlores

A study has been made, under conditions for telomerization catalysed by a redox system, of the reactivities of styrene, acrylonitrile and monochlorotrifluoroethylene with respect to some telogens viz various chloroethanes, methyl trichloroacetate, CCl₂F.CClF₂ and CClF₂.CClF1. Generally, the selected catalyst system led only to products of monoaddition; these products were isolated and identified.     

Analysis and reconstruction of a pulsed jet in crossflow by multi-plane snapshot POD

In this work, snapshot proper orthogonal decomposition (POD) is used to study a pulsed jet in crossflow where the velocity fields are extracted from stereoscopic particle image velocimetry (SPIV) results. The studied pulsed jet is characterized by a frequency f = 1 Hz, a Reynolds number Re _j  = 500 (based on the mean jet velocity ${\overline{U}_{j}}$  = 1.67 cm/s and a mean velocity ratio of R = 1). Pulsed jet and continuous jet are compared via mean velocity field trajectory and Q criterion. POD results of instantaneous, phase-averaged and fluctuating velocity fields are presented and compared in this paper. Snapshot POD applied on one plane allows us to distinguish an organization of the first spatial eigenmodes. A distinction between “natural modes” and “pulsed modes” is achieved with the results obtained by the pulsed and unforced jet. Secondly, the correlation tensor is established with four parallel planes (multi-plane snapshot POD) for the evaluation of volume spatial modes. These resulting modes are interpolated and the volume velocity field is reconstructed with a minimal number of modes for all the times of the pulsation period. These reconstructions are compared to orthogonal measurements to the transverse jet in order to validate the obtained three-dimensional velocity fields. Finally, this POD approach for the 3D flow field reconstruction from experimental data issued from planes parallel to the flow seems capable to extract relevant information from a complex three-dimensional flow and can be an alternative to tomo-PIV for large volume of measurement.     

Synthese de polymeres liquides par reaction de telomerisation entre le butadiene et le tetrachlorure de carbone

This abstract deals with the telomerization of butadiene with carbon tetrachloride. By changing experimental conditions (the nature of the catalyst [Cu⁺, Cu²⁺, Fe³⁺, Fe (CN)₆^3?, Fe (CN)₆^4?, Mg], the ratio “r” of the concentration of taxogen to that of telogen, the ratio “c” of the concentration of catalyst to that of telogen) we have obtained chlorinated liquid polymers; their molecular weights range between 208 and approx 70,000. The dispersity of these polymers is calculated to be between 1.4 and 1.6. Addition 1–4 is the most frequent, (>80%). The correspondence between ratios r and c and the average molecular weight is established.     

Synthèse de nouveaux polyesters insaturés styrèniques à partir de diols isomoléculaires à ponts thio-éthers. Étude par RMN et tenue thermique

The synthesis of unsaturated polyesters cross-linked by means of styrene have been carried out from high isomolecular weight diols containing thio-ether bonds. The ¹H-NMR peaks have been attributed. Those polyesters exhibit softness to a certain extent in conjunction with relatively high degradation temperatures (T_d 400°C).