Fulvio Andruzzi

Side-chain liquid-crystalline polyesters for optical information storage

We report erasable holographic recording with a resolution of at least 2500 lines/mm on unoriented films of side-chain liquid-crystalline polyesters. Recording energies of approximately 1 J/cm2 have been used. We have obtained a diffraction efficiency of approximately 30% with polarization recording of holograms. The holograms can be erased by heating them to approximately 80°C for approximately 2 min and are available for rerecording.

Polyether-polyester block copolymers by non-catalysed polymerization of ɛ-caprolactone with poly(ethylene glycol)

Abstract The polymerization of ɛ-caprolactone (CL) with poly(ethylene glycol) (PEG) of low molecular mass was carried out in bulk at 185°C. Gel permeation chromatographic analysis of polymerization mixtures indicated quantitative incorporation of CL monomer into PEG without formation of CL homopolymer. Characterization by infra-red and 1 H nuclear magnetic resonance spectroscopy of the resulting polymeric products, with respect to their structure, end-groups and composition, showed that these are best described as ether-ester block copolymers, whose polycaprolactone chain can be regulated by changing the amount of reacted CL. All the copolymers examined were crystalline, as confirmed by differential scanning calorimetric analysis, and showed different thermal behaviours depending on their composition.

Novel biphotonic holographic storage in a side‐chain liquid crystalline polyester

We report novel biphotonic holographic storage of text and gratings on unoriented films of a side‐chain liquid crystalline polyester capable of high density storage and complete erasure. The holograms have a typical size of 1 mm. The recording utilizes unusual photochemistry involving azo dye molecules. We believe that this technique would have a great potential in the recording of thousands of holograms in a two‐dimensional plane, as for instance in text retrieval systems and in the fabrication of high density interconnects in optical neural networks.

Side-chain liquid crystalline polyesters for optical information storage†

We report erasable holographic recording with a resolution of at least 2500 lines/mm on unoriented films of sidechain liquid-crystalline polyesters. Recording energies of approximately 1 J/cm(2) have been used. We have obtained a diffraction efficiency of approximately 30% with polarization recording of holograms. The holograms can be erased by heating them to approximately 80 degrees C for approximately 2 min and are available for rerecording.

Preparation and characterization of aliphatic diphenyl esters intended as precursors for polyesters

Abstract An extensive number of aliphatic diphenyl esters, C6H5OOC(CH2)nCOOC6H5 (n=0,...,8,10,11,12,14), have been prepared in pure form. The crystalline melting points of these esters exhibit an odd-even temperature behaviour, with the higher-melting even series (n even) displaying a minimum for n = 8 while the odd series shows an almost monotonic slow increase. High-resolution 13C nuclear magnetic resonance (n.m.r.) spectroscopy of the esters in CDCl3 and C6D6 allows all non-symmetrical carbons to be resolved, even the seven different methylenes for n = 14. This unusual spectral sensitivity is primarily based on similar data from phenyl esters, interpreted as the results of an apparent macrocyclic conformation of the larger diphenyl esters. High-performance size exclusion chromatography (s.e.c.) of diphenyl esters, phenyl esters, aromatic and linear hydrocarbons in tetrahydrofuran, toluene and chloroform points to specific phenyl ester-solvent interactions, which obscure a potential s.e.c. conformational analysis of the diphenyl esters.

Synthesis and characterization of polymers from β-propiolactone and poly(ethylene glycol)s

Abstract Uncatalysed polymerizations of β-propiolactone with low-molecular-weight poly(ethylene glycol)s were carried out in bulk, at temperatures in the range of 70 to 120°C. 1 H nuclear magnetic resonance (n.m.r.) and differential scanning calorimetry (d.s.c.) measurements on the resulting products indicated a block copolymer structure. Gel permeation chromatography (g.p.c.) and d.s.c. analyses showed that in some cases the copolymerization is accompanied by homopolymerization of β-propiolactone, probably due to the presence of residual water in the poly(ethylene glycol). N.m.r. and infra-red (i.r.) spectra of copolymers revealed the presence of hydroxyl and carboxyl end groups. The copolymerization reaction may be visualized as a two-step process, in which the ring opening of β-propiolactone takes place on both the hydroxyl groups of poly(ethylene glycol), followed by repetitive monomer addition forming an ester-ether-ester triblock copolymer.

Synthesis and characterization of new chiral mesogenic monomers

Abstract New mesogenic monomers carrying substituted biphenylyl rings linked to acryloyl or methacryloyl moieties through straight or chiral flexible spacers have been synthesized. All the investigated monomers, independent of the side group chirality, have been found to form ordered smectic phases, most probably of the S1 type. The asymmetric methyl substitution on the flexible spacer leads to an expansion of the temperature range of mesophase stability. The chiral monomers induce a helical structure when mixed with appropriate nematogens. The fingerprint texture of a contact mixture of the chiral methacrylate prepared in this work, with a nematic methacrylate synthesized previously, has been found not to change after UV-initiated polymerization.

Synthesis and characterization of comb-shaped polyesters based on 2-octadecyl-1,3-propanediol and phthalic acids

Abstract Three isomeric poly(2-octadecyl-1,3-trimethylene phthalate)s were prepared by melt transesterification of the corresponding diphenyl ester and 2-octadecyl-1,3-propanediol. Intrinsic viscosity, size exclusion chromatography and light scattering determinations yielded weight-average molecular masses of 110 000 and higher. High-resolution, solution 13C n.m.r. spectroscopy analysis of both the diphenyl ester precursors and polyesters identified the main-chain units, the isomeric aromatic acid residue and glycol carbons, the linking and the terminal ends of the octadecyl side chain, and finally allowed detection of phenyl ester end groups at 1–2% level. No absorption band due to hydroxyl end groups was monitored in the i.r. polyester spectra. I.r. spectroscopy, d.s.c. and powder X-ray diffractometry provided a clear indication of the crystallinity of the prepared polyesters. The relevant melting enthalpy values and X-ray diffraction patterns were typical of comb-shaped polymers in which the paraffinic side chains crystallize independently with their characteristic hexagonal packing.

Comb-shaped polyesters of aliphatic dicarboxylic acids and 2-octadecyl-1,3-propanediol: 1. Synthesis and microstructure

Abstract Comb-shaped polyesters are prepared by polytransesterification of 2-octadecyl-1,3-propanediol and diphenyl suberate, sebacate, dodecanedioate, tetradecanedioate and hexadecanedioate in turn. The developed melt polycondensation procedure generally results in polyesters with intrinsic viscosities in the range 0.76–1.28 dl g −1 . High performance size exclusion chromatography reveals symmetrically shaped traces with peak maxima corresponding to molecular masses in the range 48 000–65 000 by use of the universal calibration. These molecular masses equivalent to degrees of polymerization, 97–124, can be shown to result from total functional group conversions > 98.5%. Detailed 13 C nuclear magnetic resonance investigations of polyester solutions reveal many structural features originating from both main- and side-chain carbons and point to lack of stereoregularity. Infra-red spectra of polyesters reveal characteristic polyester absorption bands including bands indicative of the existence of a crystalline phase.

Temperature dependence of the 720 cm−1 IR band of poly(octadecyl ethylene) and poly(octadecyl ethylene oxide) studies on comb-like polymers III

SummaryThe dependence of the 720 cm−1 I.R. band upon the temperature has been investigated for isotactic and atactic samples of poly (octadecyl ethylene oxide) and poly (octadecyl ethylene). It is known in fact that a splitting of the band associated with the rocking vibration of methylene sequences can be correlated with orthorhombic packing of these latter.The results indicate that, besides isotactic poly (octadecyl ethylene), also the atactic polyolefin and the isotactic and atactic polyethers have orthorhombic packed chains provided that the temperature is sufficiently low. The orthorhombic to hexagonal transition takes place on a wide temperature range.