Baki Hazer

Preparation of block copolymers using a new polymeric peroxycarbamate

Abstract Block copolymers of poly(styrene- b -methyl methacrylate), poly(styrene- b -n-butyl methacrylate) and poly(methyl methacrylate- b -styrene) have been prepared via chemical reactions. A new polymeric peroxycarbamate is synthesized by reacting equimolar amounts of an aliphatic diisocyanate with a dihydroperoxide. This compound is an effective polymerization initiator, and is used to prepare active prepolymers containing fragments of polymeric peroxycarbamate. A second vinyl monomer is then incorporated to produce various block copolymers. Styrene contents, intrinsic viscosities and chemical and mechanical properties of the copolymers were determined.

Bacterial production of poly-3-hydroxyalkanoates containing arylalkyl substituent groups

6-Phenylhexanoic acid (6PHxA), 7-phenylheptanoic acid (7PHpA), 9-phenylnonanoic acid (9PNA), 11-phenylundecanoic acid (11PUA), 9-p-tolylnonanoic acid (9TNA) and 9-p-styrylnonanoic acid (9SNA) were prepared and evaluated as substrates for cell growth and polyester production by Pseudomonas oleovorans and Pseudomonas putida. P. putida was more effective than P. oleovorans for producing polyesters from these aromatic substrates. Poly-3-hydroxyalkanoates, PHAs, were obtained from 6PHxA, 7PHpA, 9PNA and 11PUA. The PHAs produced from all of these substrates contained mostly 3-hydroxy-5-phenylvalerate (H5PV) and 3-hydroxy-6-phenylhexanoate (H6PHx) units. Polymer yields ranging from 3 to 47% of cell dry weight were obtained with molecular weights ranging from 156 000 to 37 000 and polydispersities from 2.3 to 2.9. Cofeeding of most of these substrates with nonanoic acid produced mixtures of two different PHAs with different glass transitions, one in the region of −8 to 12°C for the PHA with arylalkyl substituent groups, and one in the region of −14 to −35°C for the PHA from nonanoic acid. The PHA from 9TNA also had a crystalline melting transition.

Cationic polymerization of tetrahydrofuran initiated by difunctional initiators. Synthesis of block copolymers

Abstract Cationic polymerization of tetrahydrofuran (THF) initiated by difunctional peroxidic initiators bis(4-bromomethyl benzoyl) peroxide and 2,5-dimethyl 2,5-di(4-bromomethyl benzoyl peroxy)hexane is described. Poly-THF samples possessing peroxidic groups thus obtained were used in the polymerization of styrene at 80° to obtain THF-styrene block copolymers in high yields.

Poly(styrene peroxide) and Poly(methyl methacrylate peroxide) for Grafting on Unsaturated Bacterial Polyesters

A new soluble terephthaloyl oligoperoxide (OTP) was synthesized by the reaction of terephthaloyl peroxide and 2,5-dimethyl 2,5-dihydroperoxy hexane. Thermal polymerization of vinyl monomers (styrene, methyl methacrylate) with OTP yielded poly(styrene peroxide) (PS-P) and poly(methyl methacrylate peroxide) (PMMA-P) which are used in the grafting reactions onto medium chain length unsaturated bacterial polyester obtained from soybean oily acids with Pseudomonas oleovorans poly(3-hydroxy alkanoate), (PHA). PS-g-PHA and PMMA-g-PHA graft copolymers isolated from related homopolymers were characterizated by 1H NMR spectrometry, FT-IR spectroscopy, thermal analysis and gel permeation chromatographic (GPC) techniques. Swelling measurement of the crosslinked graft copolymers were also measured to calculate qv values.

Preparation of poly(ethylene glycol) grafted poly(3-hydroxyalkanoate) networks

Poly(3-hydroxyalkanoate)-g-poly(ethylene glycol) crosslinked graft copolymers are described. Poly(3-hydroxyalkanoate)s containing double bonds in the side chain (PHA-DB) were obtained by co-feeding Pseudomonas oleovorans with a mixture of nonanoic acid and anchovy (hamci) oily acid (in weight ratios of 50/50 and 70/30). PHA-DB was thermally grafted with a polyazoester synthesized by the reaction of poly(ethylene glycol) with MW of 400 (PEG-400) and 4,4′-azobis(4-cyanopentanoyl chloride). Sol-gel analysis and spectrometric and thermal characterization of the networks are reported.

Polystyrene-b-polydimethyl siloxane (PDMS) multicomponent polymer networks: Styrene polymerization with macromonomeric initiators (macroinimers) having PDMS units

Abstract A new macromonomeric initiator (macroinimer) was synthesized and evaluated for the bulk polymerization of styrene at 60 and 80°C. The macroinimer containing poly(dimethylsiloxane), PDMS, was synthesized via condensation reactions between 4,-4′-azobis-4-cyanopentanoyl chloride (ACPC), PDMS and methacryloyl chloride. The product (MIM I) was thermally homopolymerized and copolymerized with styrene in bulk. Kinetics of radical polymerization of styrene with MIM I at 60°C and at low conversion was studied. Rate constant K, kp(fkd/kt)1/2, was estimated from kinetic data as 1.15 × 10−4 11/2 mol−1/2 s. Bulk polymerization of styrene with macroinimers at 80°C gave crosslinked block copolymers. D.s.c. measurements showed that crosslinked block copolymers had a glass transition temperature around 45°C. This is evidence of a plasticizing effect of flexible polysiloxane segments in copolymers. Crosslinked PDMS-b-PS block copolymers obtained using macroinimers may be an interesting group of thermoplastic elastomers.

Polymerization of acrylamide by the redox system cerium(IV) with poly (ethylene glycol) with azo groups

Abstract Polymerization of acrylamide using Ce(IV) with poly(ethylene glycol) having azo and hydroxyl functions, was carried out to yield acrylamide-(ethylene glycol) block copolymers with labile azo linkages in the main chains. These prepolymers were used to induce the radical polymerization of acrylonitrile and acrylamide through the thermal decomposition of the azo group, resulting in the formation of multiblock copolymers.

Synthesis of styrene-tetrahydrofuran branched block copolymers

Abstract A new multifunctional cationic initiator, bis (3,5-di-bromemethyl benzoyl) peroxide, was synthesized from 3,5-dibromomethyl benzoyl bromide and sodium peroxide. The initiator was treated with silver hexafluoroantimonate to prepare branched polytetrahydrofuran (poly-THF) with four arms. Branched poly-THF having the peroxide group in the chain were used in the polymerization of styrene (St) at 80° to obtain THF-St branched block copolymer in high yield.

Preparation and characterization of block and graft copolymers using macroazoinitiators having siloxane units

α,ω-Amine terminated organofunctional polydimethylsiloxane (PDMS) was condensed with 4,4′-azobis-4-cyanopentanoyl chloride (ACPC) to prepare macroazoinitiators containing siloxane units. Interfacial polycondensation reaction at room temperature was applied: ACPC was slightly dissolved in carbon tetrachloride and it was poured on aqueous NaOH solution of PDMS. Block copolymers containing PDMS as a block segment combined with polystyrene (PS) have been derived by the polymerization of styrene monomer initiated by these macroazoinitiators. PS-b-PDMS block copolymers were characterized by using nuclear magnetic resonance and infrared spectroscopy. Thermal and mechanical properties of the block copolymers were studied by using thermogravimetric analysis, differential scanning calorimetry, and a Tensilon stress-strain instrument. The morphology of block copolymers was investigated by scanning electron microscopy. PDMS-g-polybutadiene (PBd) graft copolymers were also prepared by reaction of PBd with the above macroazo-initiator. Increase in the amount of macroazoinitiator in the mixture of PBd (52% w/w) leads to the formation of crosslinked graft copolymers. Molecular weights of soluble graft copolymer samples were between 450 and 600 K with a polydispersity of 2.0–2.3.

Synthesis of PS-PEG and PMMA-PEG Branched Block Copolymers by Macroinimers

Abstract A new type of macroinimers were synthesized by the capping reaction of hydroxyl groups of polyazoesters with isocyanato ethyl, methacrylate in the presence of dibutyl tin dilaurate. Macroinimers having PEG-400 and PEG-1500 units were used in the polymerization of methyl methacrylate (MMA) or styrene (S) to obtain PS-PEG or PMMA-PEG branched block copolymers at 60°C. Longer polymerization times or higher macroinimer concentrations led to cross-linked block copolymers. Similarly neat homopolymerization of macroinimers also led to the cross-linked polyethyleneglycols. The products were characterized by IR and NMR spectroscopy, viscosity measurements and fractional precipitation.