Ezzatollah Khoshdel

X-ray analysis of some porphyrin and polymer Langmuir-Blodgett films

Derivatives of mesoporphyrin IX dimethylester, poly(octadec-1-ene-maleic anhydride) and poly(styrene-maleic anhydride) have been prepared as Langmuir-Blodgett (LB) films. Examining their layer structure using X-ray diffraction analysis has led to several interesting and important conclusions about their packing arrangement.

Langmuir-Blodgett films from preformed polymers: derivatives of octadec-1-ene-maleic anhydride copolymers

Abstract We show here that good quality Langmuir-Blodgett films of octadec-1-ene- maleic anhydride copolymer derivatives can be deposited onto a number of substrates. The effects on the isotherm, deposition and packing of a number of derivatives are studied and these copolymers compared with a number of possible alternative amphiphilic polymer systems.

Michael additions catalysed by cinchona alkaloids bound via their vinyl groups to preformed crosslinked polymers

Cinchona alkaloids have been satisfactorily bound via their vinyl groups to crosslinked polymers containing thiol residues. The products have been used to catalyse one or more of the following Michael additions: the additions of (1) thio-p-cresol, (2)p-chlorothiophenol, and (3) thiobenzoic acid to cyclohex-2-en-1-one, and (4) of toluene-α-thiol to 2-nitrostyrene. The steric course of reactions (1)–(3) is dominated by the configurations of C-8 and C-9 in the alkaloids, but the nature of the C-3 group does have an effect and this probably explains why the optical yields obtained using the polymer-supported catalysts were lower than those obtained using the free alkaloids. The optical yields obtained in reaction (4), though small, did not follow this pattern. The polymers afforded higher optical yields than the free alkaloids and, in one case, the predominant enantiomer was of opposite configuration.

Lightguiding in Langmuir-Blodgett films of preformed polymers

Abstract Preformed polymers, made from derivatives of vinyl-maleic anhydride co-polymers, have been used to produce thick (300–400 layers; 0.5–0.6 μm) Langmuir-Blodgett multilayers. The thermal stability of the films is shown to depend on the relative positions of the side-groups. Those materials which deposited well for large numbers of layers and possessed thermal stability were investigated for evidence of optical waveguiding using light at a wavelength of 633 nm. An attenuation of approximately 10 dB cm -1 was observed in films having a thickness of about 0.5 μm after suitable precautions were taken to exclude dust and bacteria.

An investigation of liquid-crystal side-chain polymeric Langmuir-Blodgett films as optical waveguides☆

Abstract Various long-chain vinyl compounds, including some prepared from commercial liquid crystals, have been copolymerized with maleic anhydride and then the anhydride residues in the products have been reacted with methanol to give acid residues and methyl ester residues. All the materials have been deposited as Langmuir-Blodgett films onto hydrophobic quartz slides using a computer- controlled trough. Prior to investigation of the optical waveguiding in the films, prism coupling techniques have been employed to analyse their various propagation modes.

Films formed from co-polymers containing azobenzene side groups

Co-polymers of styrene-maleic anhydride have been synthesised with a number of different loadings of azobenzene-containing side groups and formed into thin films by casting and by the Langmuir-Blodgett technique. By illumination with polarised white light, appropriately loaded materials cast as films could be transformed from isotropic to uniaxial structures that exhibited dichroism and birefringence of Delta n=0.21.

Michael reactions catalysed by polymer-supported quaternary ammonium salts derived from cinchona and ephedra alkaloids

Reaction of chloromethylated crosslinked polystyrenes with cinchonidine, cinchonine, or (–)-N-methylephedrine gave polymer-supported chiral quaternary ammonium chlorides. The hydroxide, hydrogen carbonate, fluoride, and chloride forms of these polymers, and also of a commercial polymer containing achiral quaternary ammonium groups, catalyse one or more of the following Michael reactions: (1) The addition of methyl 1-oxoindan-2-carboxylate to methyl vinyl ketone, (2) the addition of ethyl 2-oxo-cyclohexanecarboxylate to methyl vinyl ketone, and (3) the addition of thio-p-cresol to cyclohex-2-enone. Catalysts prepared from cinchonidine achieve optical yields of ⩽27% of the S-adduct from reaction (1), whilst those catalysts prepared from cinchonine achieve optical yields of ⩽13% of the R-adduct. This is one of the few instances where the use of polymer-supported chiral quaternary ammonium salts has given substantial optical yields. With reactions (2) and (3) the optical yields were all <2.5%. The catalysts are chemically fragile but, at least with reaction (1), can be re-used several times.

Conversion of alcohols into alkyl bromides using polymer-supported triphenylphosphine dibromide and polymer-supported triphenylphosphine and carbon tetrabromide

Alcohols were converted into alkyl bromides by reaction with polymer-supported triphenylphosphine dibromide and with polymer-supported triphenylphosphine and carbon tetrabromide. With both reagents excellent yields of bromides were obtained, but the reactions with the latter reagent were faster and cleaner and in favourable cases high yields of bromide were obtained within 15 min at 20 °C. An advantage of the polymer-supported reagents is that product isolation is facilitated by the ready separation of the supported from the non-supported species.

Preparation and chemical reactions of some polymer-supported steroids

Abstract Steroidal acids and alcohols were satisfactorily bound via ester linkages to functionalised polystyrenes, and subsequently were satisfactorily detached. Best loadings were achieved by reacting polymers with acid chloride residues with steroidal alcohols in refluxing ethylbenzene. However, there appears to be a loading limit in this system corresponding to about 2.5 polymer repeat units per steroid molecule. Ketone groups in bound steroids were reduced using sodium borohydride in various solvents or aqueous potassium borohydride in phase transfer systems. The proportions of the epimeric alcohols obtained were compared with those obtained from low molecular weight analogues. The polymer appears to have very little effect on the proportions obtained, except when aqueous reagents are used and the polymer is macroporous. Olefinic groups in bound steroids were epoxidized or hydrogenated.

Preparation of some polymer-supported crown ethers and their use as phase-transfer catalysts

Benzo-15-crown-5 and dibenzo-18-crown-6 have been formylated. The products were then bound to diol-containing crosslinked polystyrenes via acetalisation and to crosslinked polymers containing benzyltriphenylphosphonium chloride residues (obtained by treating chloromethylated polystyrenes with triphenylphosphine)via phase-transfer catalysed Wittig reactions. The various polymer-supported crown ethers have been found to be satisfactory phase-transfer catalysts for the reactions of n-octyl bromide in toluene with aqueous potassium iodide at 90 °C and with aqueous sodium p-methylthiophenolate at 80 °C, but not for the reaction of n-octyl bromide in toluene with aqueous potassium cyanide at 90 °C. The crosslinked polymers containing benzyltriphenylphosphonium chloride residues were also satisfactory catalysts for the first two reactions.