323,402 research outputs found
Azobenzene containing polymers: what is yet viable with aged liquid crystals
No full textA Commentary on the paper ”Photochromic liquid crystalline polymers. Main chain and side chain polymers containing azobenzene mesogens„, by A. S. Angeloni, D. Caretti, C. Carlini, E. Chiellini, G. Galli, A. Altomare, R. Solaro and M. Laus. First published in Liquid Crystals, 4, 513‐527 (1989)
Statistical calibration for the evaluation of public services : a non-standard approach for quality measurement
No full text
Synthesis and characterization of segmented hydrosoluble poly(tartaramide)s
No full textSegmented poly(tartaramide)s were prepared by polycondensation of monodispersed alpha,omega-diaminooligo(ethyleneglycol)s, with oligomerization degree included between 2 and 6, with two optically active dialkyl tartrates. The diamines were obtained from the relevant commercial glycols using a modified Gabriel synthesis. The polycondensations were performed in methanol at 55 degrees C with triethylamine as catalyst. By this route, optically active poly(tartaramide)s, with oligomerization degree in the 4-10 range, were obtained in fairly high yields. Solubility and thermal properties of the-polycondensation products were found to be related to the length of the oligo(oxyethylene) segment and to the presence of free hydroxyl groups
Francesco De Sanctis a scuola dallo zio Carlo
No full textIl contributo tratta della formazione classica di Francesco De Sancti
Poly(ester-sulphide)s from oligo(oxyethylene)dithiols and diacrylates
No full textPoly(β-thioesters) were synthesized by Michael-type base-catalyzed polyaddition of oligo(ethylene glycol)α,ω-dithiols to bis(acrylic esters). Fine tuning of the hydrophilic–hydrophobic balance of the polymers can be achieved by modulating the length of the oligo(ethylene glycol) segment and the nature of the spacer between the two ester groups in the bis(acrylate) moiety. Investigation of the reactivity of oligo(ethylene glycol)dithiols with acrylic systems is reported, with the aim of determining the best conditions for a polyaddition process involving the base catalyzed addition of such dithiols to bis(acrylate) systems. Some hypotheses are proposed for the role of the solvent and of the catalyst. The influence of the molecular structure of the reactants on reactivity and on the properties of the resulting polymers is also discussed
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