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We examined the effect of the addition of homopolymers tetramethylbisphenol A polycarbonate, TMPC, and poly(norbornene−methyl-d3-carboxylate), NBMC, on the interlamellar spacing and the phase stability of symmetric poly(styrene-b-methyl methacrylate) diblock copolymer thin films on silicon substrates. The films were of thickness h, L 0.2 the morphology of the diblock copolymer changed to accommodate higher volume fractions of TMPC. This behavior is contrasted with earlier observations in the PS-b-PMMA/PS homopolymer system wher...

A recent application of density functional theory to the structure and thermodynamics of the ordering of symmetric, tangent hard site, diblock copolymers [S. K. Nath et al., J. Chem. Phys. 106, 1950 (1997)] predicted an interfacial thickness larger than would be expected from previous self-consistent-field studies of thread chains. Here we compare the theoretical predictions with the few experimental measurements of interfacial thickness in symmetric diblocks. It is observed that predictions of the thickness of the interface are sensitive to the details of the monomer structure included in the underlying model, and that the range of the experimental measurements is spanned by the two theoretical models.

Polymer reference interaction site model (PRISM) based density functional (DF) theory is used to evaluate the structure and thermodynamics of structurally symmetric, freely jointed, diblock chains with 0.50 volume fraction. These results are compared to the results of self-consistent-field (SCF) theory. Agreement between the predictions of the SCF and DF theories is found for the lamella spacing well above the order–disorder transition (ODT) and for the qualitative behavior of the interfacial thickness as a function of both chain length and Flory–Huggins χ parameter. Disagreement is found for the magnitude of the interfacial thickness where DF theory indicates that the thickness is 1.7±0.2 times larger than that predicted by SCF theory. It appears that behavior on the monomer length scale is sensitive to system specific details which are neglected by SCF theory.

Polyatomic density functional theory is applied to a binary polymer blend. The polymer reference interaction site model (PRISM) liquid state theory provides the homogeneous state correlation functions necessary for the application of density functional theory. An effective chi parameter can be recognized from the density functional expression; however, the phase separation criteria does not depend solely upon the chi parameter, rather it depends upon various combinations of the species-dependent direct correlation functions of the blend. The Flory-Huggins chi parameter along with the associated phase diagram is obtained when the monomer volumes of the blend species are equal and for a range of monomer-monomer attractive interactions. Calculations are performed both with and without the assumption of incompressibility. The density functional theory along with the PRISM determined “input” predict that an isotopic polymer blend shows an upper critical solution temperature (UCST) phenomena. © 1995 John Wiley & Sons, Inc.

Novel molybdenum alkylidyne [(F3C)Me2CO]2Mo(C-t-Bu)[N(Ar)PC(H)(CMe2Ph)] (Ar = 2,6-(i-Pr)2C6H3; 3b) is formed in the reaction of tert-butylphosphaalkyne 2 with molybdenum alkylidene 1b. Alkylidyne 3...

The phosphametallacycle 3, [ArN][RO]MoC(t-Bu)P(OR)C(H)(t-Bu) (Ar = 2,6-(i-Pr)2-C6H3, R = CMe(CF3)2), is formed from the cycloaddition of tert-butylphosphaacetylene to the high-oxidation-state molybdenum alkylidene [ArN][RO]2MoC(H)(t-Bu), accompanied by an alkoxide metal-to-ligand shift. The 1-phospha-3-molybdacyclobut-2-ene has been characterized by multinuclear NMR spectroscopy and its molecular structure determined by X-ray crystallographic analysis.

The synthesis of amphiphilic star block copolymers by ring opening metathesis polymerization using a new cross-linking agent and appropriately functionalized norbornene-type monomers is reported

A variety of organic and hybrid organic-inorganic polymer systems were prepared and evaluated for their bulk response to optical, thermal and chemical environmental changes. These included modeling studies of polyene-bridged metal porphyrin systems, metal-mediated oligomerization of phosphaalkynes as heteroatomic analogues to polyacetylene monomers, investigations of chemically amplified degradation of acid- and base-sensitive polymers and thermally responsive thermoplastic thermosets based on Diels-Alder cycloaddition chemistry. The latter class of materials was utilized to initiate work to develop a new technique for rapidly building a library of systems with varying depolymerization temperatures.

Monolayers on surfaces have become a topic of considerable interest over the last few years. This has arisen from the need to functionalize a surface so that its properties are different than the properties of the bulk material. This research has involved functionalizing copper surfaces to enhance adhesion to epoxy. We have accomplished this using block copolymers made by Ring-Opening Metathesis Polymerization (ROMP). In this paper we discuss the synthesis and characterization of these block copolymers and their segregated monolayer conformation at copper surfaces, including NMR, GPC, SANS, neutron reflectivity, and TOF-SIMS. We also discuss a comparison of block copolymers to SAMS for surface functionalization.Monolayers on surfaces have become a topic of considerable interest over the last few years. This has arisen from the need to functionalize a surface so that its properties are different than the properties of the bulk material. This research has involved functionalizing copper surfaces to enhance adhesion to epoxy. We have accomplished this using block copolymers made by Ring-Opening Metathesis Polymerization (ROMP). In this paper we discuss the synthesis and characterization of these block copolymers and their segregated monolayer conformation at copper surfaces, including NMR, GPC, SANS, neutron reflectivity, and TOF-SIMS. We also discuss a comparison of block copolymers to SAMS for surface functionalization.

Functionalized block copolymers were synthesized as adhesion promoters using Ring-Opening Metathesis Polymerization (ROMP). They were designed for glass/epoxy and copper/epoxy interfaces. The former contained triethoxysilane groups in the first block and secondary amine groups in the second. The latter contained imidazole groups in the first and amine groups in the second block. These block copolymers were shown to form ordered monolayers on the respective glass and copper surfaces using neutron reflectivity. Adhesion measurements showed an enhancement of adhesion after application of these block copolymers.

The Langmuir-Blodgett (LB) technique has been used to form two different types of multilayer films with novel molecular organizations. In the first case, a new method of fabricating superlattices of conducting polymers has been devised and studied. This method involves forming polyion complexes of acid derivatized conducting polymers with stearylamine (StNH2) and subsequently manipulating them into AB type superlattices by the LB technique. To date, superlattices consisting of isolated alternating monolayers of poly(thiophene acetic acid) (PTAA) and sulfonated polyaniline (PAn) have been studied. The layered structure of these films was found to be very similar to that of their respective homopolymer LB films, as evidenced by X-ray diffraction patterns. The conductivity of these superlattices was in the range of 10−1 S/cm, which is approximately one order of magnitude higher than that obtained with the homopolymer LB films (about 10−2 S/cm). In the second case, LB films of a novel diblock copolymer have been made, where one of the blocks is a water-insoluble polyacetylene precursor and the other block a non-conjugated, water-soluble poly(norbornene) derivative. The precursor block of the LB films could be converted to trans-polyacetylene by heating, and doped to a conductivity of 10−3 S/cm, which was significantly higher than that of cast (10−7 S/cm) or spin-coated (10−5 S/cm) films of the same material. Thus, in both cases, the unique molecular organization created by the LB technique has resulted in films with higher conductivities than those obtained by traditional casting techniques.

Polysilsesquioxanes are a class of siloxane polymers commonly prepared by the hydrolysis and condensation of trialkoxysilanes or trichlorosilanes. From a trifunctional monomer one would expect the organically-modified polymers to be highly crosslinked and insoluble resins. However, while some silsesquioxane monomers with R = H, CH{sub 3}, or vinyl do form crosslinked polymers capable of forming gels, the majority react to form soluble oligosilsesquioxanes, including discrete polyhedral oligomers, and polymers. Because of their solubility, ladder structures have been proposed. However, viscosity studies by Frye indicate that the polyphenylsilsesquioxane is more likely best represented by a polymer rich in both cyclic structures and branches, but without any regular stereochemistry. In this study, the authors have examined the hydrolysis and condensation polymerizations of phenyltrialkoxysilane, benzyltrialkoxysilane, and 2-phenethyltrialkoxysilane monomers under both acidic and basic conditions. The resulting phenyl, benzyl and phenethyl-substituted polysilsesquioxanes were characterized by {sup 1}H, {sup 13}C, {sup 29}Si NMR, gel permeation chromatography, and differential scanning calorimetry. The effects of the organic substituent (phenyl, benzyl, phenethyl), alkoxide group (OMe, OEt), catalyst (HCl, NaOH), monomer concentration, and polymer processing on polymer molecular weight and glass transition temperature were determined.