Protective coatings for both titanium-aluminum (Ti-Al) alloys and for carbon-carbon (C-C) composites have been synthesized and characterized for high temperature, light weight, structural applications. Coatings of choice must show protection against oxygen and hydrogen in severe environments. Aluminum-silicate glass ceramics were chosen as coating candidates because they are stable to temperatures of 1500°C, are nonreactive to oxygen, and have minimal reactivity with respect to hot hydrogen.

Sol-gel glass microcomposite processing of polybenzobisthiazole (PBZT) films increased the compressive strength of PBZT/PEEK film laminates by more than four times. The presence of glass within microfibrillar regions of PBZT/sol-gel glass microcomposite films inhibited microbuckling during compression and greatly increased resistance to compressive failure.

Studies of PBZT/sol-gel glass microcomposite film morphology conducted at UMass by E.L. Thomas and at Penn State by C. Pantano indicated sol-gel glass precursor solutions had condensed within PBZT to produce a fine-scale (100 to 300Å) granular structure, homogeneously distributed throughout PBZT lamellae of microfibrils.

In a parallel effort, we have successfully extended sol-gel microcomposite processing technology for the improvement of compressive strength in ordered polymer fibers. Details concerning our results will be discussed.

This paper addresses developments in the understanding of intra-cavity elements in ion lasers using sol-gel prepared silica. Growing interest centres around the generation of coherent light in the near u.v. spectrum. Sol-gel silica offers unprecedented levels of purity and homogeneity for critical intra-cavity applications and may well solve the problem of creating colour-centre free Brewster windows for use in the u.v.

We also report new work which makes use of the porous phase of such material and show how it is directed at one of the early bastions of photographic science – Lippmann's photography.

A series of microporous silica gels were synthesized by hydrolyzing tetramethylorthosilicate (TMOS) with varying amounts of water. No catalyst or alcohal was added. The gels were characterized by water sorption isotherms, the BET nitrogen surface area measurements, and differential thermal analysis. Although the gelation time for all H2O/TMOS molar ratios (R) was approximately the same (about 3 hr), the pore-size (pore diameter) and sorption capacity were found to be minimum in the R range 4.96–5.37 but increased with both increasing and decreasing R. Water sorption isotherms measured at 25°C after degassing at 200°C of gels prepared with R = 4.96–5.37 exhibited moderate Type I (Brunauer classification) isotherm which changed to intermediate between Type I and Type IV with decreasing or increasing R. These results indicated that the amount of organic or water which was not utilized in the reaction and the degree of cross-linking apparently played a role for the observed variations in pore-size or shape of water isotherms.

We describe the alignment behaviour of different liquidcrystalline (LC) side-chain polymers when they are subjected to electrical/thermal treatments. It is shown that the alignment behaviour is determined by several variables for a given polymer, including the amplitude and frequency of the applied electric field and both the thermal and electrical history of the sample and its low-field dielectric relaxation properties. It is shown that the dielectric relaxation spectra vary systematically with the degree of macroscopic alignment of the sample and its temperature. The anisotropy of dielectric properties may be understood in terms of the anisotropic reorientational motions of the dipolar mesogenic groups. The permittivity data allow the degree of macroscopic alignment to be determined, via a director order parameter Sd for samples prepared in different ways and also for samples being realigned, as a function of time, by directing electric fields. We illustrate these principles through data we have obtained for a copolymer having the mesogenic groups attached longitudinally and transversely to the main chain.

The in-situ polymerisation of reactive thermotropic and lyotropic liquid crystals affords a method of processing new polymers with anisotropic ultrastructures.

Magnetic susceptibility data (300–520 K) of monomeric and dimeric mesogenic copper(II) compounds are presented. Different magnetic effects arising from the paramagnetic Cu(II)-centres and the diamagnetic anisotropy of the mesogenic groups are observed and discussed with respect to possible inter molecular interactions.

Using broad band dielectric spectroscopy on well oriented microdomains of mesogenic polymethacrylates the influence of strong lateral dipole groups on the dielectric parameters could be verified. The mesogenic groups investigated were phenylbenzoates with fluorine substituents at the phenyl ring. The orientation of the samples was maintained in a superconducting magnet with field strength of 7.2 T. The results are compared with those obtained for non-substituted compounds.

In an attempt to synthesize side chain liquid crystalline polymers containing NLO active moieties, a number of psubstituted aromatic azomethine phenols with donor-acceptor substituents such as N≡C and NO2 were prepared and incorporated into a polymer chain as side groups.

Liquid crystalline properties of intermediate compounds composed of such moieties were explored separately and in mixtures. Phase diagrams were established. These intermediate compounds of M2C8 and M5C8 show interesting mesogenic properties.

Methacrylic esters with such moieties were also synthesized. Homopolymer and copolymer systems with donor-acceptor substituents were obtained. Such copolymers also display liquid crystalline properties.

Chiral nematic copolymers based on optically active cholesterol, dihydrocholesterol, (R)-(+)- and (S)-(−)-1-phenylethylamine, and (+)- and (−)- isopinocampheol were synthesized and characterized for the investigations of thermotropic and optical properties. Although helical sense does not appear to correlate with the sign of [α]D of the precursor chiral compound as suggested by the observations of cholesteryl and dihydrocholesteryl copolymers, the inversion of chirality in the pendant group, (R)-(+)- vs (S)-(−)-1-phenylethylamine, does lead to the opposite handedness in the resultant helical structure. To better understand the structure-property relationships involving helical sense and twisting power, systematic studies of the roles played by both nematogenic and chiral structures as well as other structural features of the comonomers should be conducted.

The formation of surface films of acetalized poly(vinyl alcohol)s at the air/water interface has been investigated in terms of the structure of the transferred films, after transfer of these surface films to solid substrates by means of the Langmuir-Blodgett technique. Furthermore, their electron beam exposure characteristics and non-linear optical properties were measured. It was found that the monolayers of acetalized poly(vinyl alcohol)s having aliphatic side chaines gave stable surface films with a limiting area of ca. 0.3nm2/average repeat unit, irrespective of the side-chain length and the degree of polymerization of the starting poly(vinyl alcohol). The surface films could be deposited onto various substrates with deposition ratios of 1.0. The resulting multilayers were Y type. The thickness of the multilayers was proportional to the number of layers, and the single-layer thickness increased with increasing sidechain length. The surface wettability of the multilayers changed alternatingly, depending on whether the number of layers was even or odd. These results indicated that the surface films were monolayers of polymers, with hydrophilic main chains spread over the air/water interface and hydrophobic side chains directed approximately normal to the interface. The transferred films maintained the oriented structure of the monolayers at the interface. The acetalized poly(vinyl alcohol)s prepared by the LB technique is adaptable as a high resolution negative-type EB resist. And the second harmonic generation (SHG) of some acetalized poly(vinyl alcohol)s was observed by LB method and by electric field poling method.

The pyroelectric coefficients of a range of polymers with a methacrylate backbone and nitrostilbene or nitrobipheny mesogens attached by a 3 or 6 carbon spacer have been measured in order to assess the efficiency of the poling process. It is found that the response is much lower than the guest-host system MNA in PMMA, suggesting that the polar mesogens pack anti-parallel and that this alignment is not broken by the applied field.

These strong interactions also provide an explanation for the absence of the β relaxation process in the experimental polymers and therefore the brittle nature of the films. They may also explain the stability of the polarisation achieved.

Series of poly(urethanes) were prepared in which the spacer groups between the rigid segments contained siloxanes. The conditions for the appearence of liquid crystallinity and a fair thermal stability were investigated and compared to those of corresponding esters.

Characterisations of side chain liquid crystalline polymers point towards chemical structures and processing techniques which optimise their suitablility for non-linear optical (NLO) applications. Techniques used are thermal analysis, X-ray and hotstage polarised light microscopy (orthoscopic and conoscopic).

An A/B block copolymer consists of two macromolecules bonded together. In forming an equilibrium structure, such a material may separate into distinct phases, creating domains of component A and of component B. A dominant factor in the determination of the domain morphology is area-minimization of the intermaterial surface, subject to fixed volume fractions. Surfaces that satisfy this mathematical condition are said to have constant mean curvature. The geometry of such surfaces strongly influences material physical properties. We have discovered domain structures in microphase-separated diblock copolymers that closely approximate periodic surfaces of constant mean curvature. Transmission electron microscopy and computer-simulation are used to deduce the three dimensional microstructure by comparison of tilt series with two-dimensional image projection simulations of three-dimensional mathematical models. Two structures are discussed: First is the double diamond microdomain morphology, associated with a newly discovered family of triply periodic constant mean curvature surfaces. Second, a doubly periodic boundary between lamellar microdomains, corresponding to a classically known minimal surface (Scherk's First Surface), is described.

Poly (methyl methacrylate) (PMMA) was used to improve the flexural properties of the high temperature superconducting ceramics (YBa 2Cu3O7-x). The organic polymer was impregnated into the porous ceramic at room temperature. The flexural properties were evaluated using disk specimens. The interaction between the PMMA and ceramic was studied using electron probe microanalysis (EPMA). Poly (methyl methacrylate) polymer increased the flexural strength of the superconducting ceramic without affecting its electrical properties. Flexural strength relationships have been developed for the superconducting ceramic with and without polymer. Performance of the ceramic-polymer composite was also evaluated by thermocycling between 77k and 300k.

Electrically conducting composite polypyrrole/poly(p-phenyleneterephthalamide) (PPTA or KEVLAR) fibers have been prepared by chemical polymerization of pyrrole within the interstices of the hydrogen-bonded gel structure of never-dried PPTA fibers. The resultant fibers contain a uniform dispersion of polypyrrole, as evidenced by scanning electron microscopy. The temperature dependence of the electrical conductivity of these hybrid fibers is presented. The conductivity is well described by the fluctuation-induced charge transport model over the entire temperature range of interest. However, the low temperature electrical conductivity also exhibits a hoppinglike temperature dependence, and an Arrhenius-like temperature dependence is observed in the high temperature limit. Measurements of the temperaturedependent tbermopower are indicative of a p-type carrier.

Synthesis/processing schemes for the preparation of optical quality thin films of π-electron containing organic and organometallic materials are discussed. Fabrication approaches range from preparation of molecular/polymer composites, to preparation of copolymers containing pendant electroactive moieties, to preparation of copolymers with electroactive units incorporated into the polymer backbone, to the preparation of polymer/polymer composites. Such fabrication methodologies (particularly the latter three approaches) have the advantage of facilitating control over polymer solubility and of avoiding aggregation of electroactive units. The synthetic schemes discussed here yield materials with well-defined electroactive units; thus, diffuse bandedges associated with a distribution of π-electron conjugation lengths are avoided. Degenerate four wave mixing (DFWM) measurements at 532, 579–600, and 1064 nm are used to determine third order susceptibilities. Investigation of the frequency dependence of χ(3)/α established that resonance contributions dominate non-linear optical activity near the π-iπ* bandedge. A variety of electroactive moieties have been investigated with the largest values of χ(3)/α (= 10−12 esu cm) being observed for triphenodioxazine, metal phthalocyanine, metal tetraazaannulene, 6,6′-dimethoxy-quinolidine cyanine units.

Phase diagrams of the microphase morphologies for triblock copolymer melts are calculated for the weak segregation limit. The diagrams are found to be highly asymmetric with block copolymer composition.

Carboxyl functional poly(arylene ether) oligomers of controlled number average molecular weight were synthesized via nucleophilic aromatic substitution step polymerization using p-hydroxy benzoic acid as the molecular weight and end group controlling reagents. The subsequent functionalized polyarylene ethers were copolymerized with acetoxy benzoic acid or acetoxyphenoxy benzoic acid via melt acidolysis procedures. Successful copolymers were generated using chlorobenzene as a solvent for the first s age of the reaction followed by melt reaction at temperatures as high as 325°C. Resulting copolymer composition and segment size were investigated. It was possible to prepare improved solvent resistant copolymers through incorporation of the liquid crystal polyester (LCP) segment. Extraction tests using boiling chloroform showed that a high percentage of segmented copolymer were generated. Swelling characteristics were also noted and were observed to decrease as a function of the LCP concentration utilized. Multiple transitions were observed in differential scanning calorimetry consistent with Tg's, Tm's and possibly with liquid crystal transitions. Optical microscopy showed an ordered microstructure developed which is consistent with the presence of liquid crystalline phases. The materials were successfully compression molded to afford tough coherent films at all compositions, implying the likelihood of improved compressive strength relative to the LCP homo- or copolyesters.