Synthesis and chain flexibility of poly(cyclohexylethyl methacrylate)

The synthesis and characterization of fractions of poly(cyclohexylethyl methacrylate) (PCHEM) are reported. A combination of low-angle laser light scattering and intrinsic viscosity experiments was employed to estimate the characteristic ratio (C_∞) of this polymer. The value of 10.7 obtained for PCHEM is similar to the value of 11.3 found previously for poly(phenylethyl methacrylate) but is smaller than values measured for poly(cyclohexyl methacrylate) and poly(cyclohexylmethyl methacrylate) (C_∞ = 11.6 and 11.9, respectively). Received: 28 October 1996/Revised: 16 December 1996/Accepted: 19 December 1996     

Addition polymerisation vs. ROMP on cyclic and strained olefins with the Mo(CO)5PPh3/alkylaluminums catalysts

The polymerisation of cyclic and strained monomers such as bicyclo[2.2.1]hept-2-ene (norbornene, NBE) and bicyclo[2.2.1]hepta-2,5-diene (norbornadiene, NBDE) with the catalytic systems Mo(CO)₅PPh₃/alkylaluminums was studied. From the polymers produced we demonstrate the existence of an antagonism between the ROMP (Ring-Opening-Metathesis-Polymerisation) mecanism and the olefin addition polymerisation mecanism. In addition ROMP mecanism is affected by the solvent. These catalysts also promotes the isomerisation of double bonds, as indicated by the ESR signal observed for the conjugated crosslinked polyNBDE produced by ROMP. Received: 5 August 1996/Revised version: 22 October 1996/Accepted: 25 October 1996     

Poly(3,6-carbazolylmethylene)s with flourinated and nonflourinated tapered building side groups

The syntheses of two different poly(3,6-carbazolylmethylene)s are described. The polycondensation reaction proceeds without any crosslinking and the obtained polymers were characterised by elemental analysis ¹H-NMR, ¹³C-NMR and ¹⁹F-NMR. DSC studies evidenced that one of the obtained polymers, i.e. poly[N-(3,4,5-tris(4-perflourooctylbutyl-1-yloxy)benzyl)carbazole] shows liquid crystalline behaviour and X-ray analysis pointed to a hexagonal columnar mesophase. Received: 10 October 1996/Revised: 20 November 1996/Accepted 20 November 1996     

One-pot syntheses of water-soluble poly(oxamide)s

Two kinds of water-soluble polymers were synthesized by using the poly(oxamide) polyanion generated in situ from the reductive coupling polymerization of diisocyanates induced by SmI₂. One is a nonionic polymer bearing oligo(ethylene oxide) pendants, which was obtained by treating the polyanion with α-methyl-ω-(4-bromomethyl)phenylmethyl oligo(ethylene oxide). The other is an ion-containing polymer having sulfonate moieties in the side chains, which was prepared by the reaction of the polyanion with 1,3-propane sultone or sodium 4-(bromomethyl)-benzenesulfonate. In both cases, the corresponding polymers were provided in good yields, and their solubilities were found to be dependent on the structure as well as the substitution degree. The poly(oxamide) with oligo(ethylene oxide) exhibited good solubilities in common organic solvents and was soluble in aqueous system at high level of substitution. On the other hand, the poly(oxamide) with propane-sulfonic acid showed high solubility in both acidic and basic water but was insoluble in organic solvents, while the poly(oxamide) having benzylsulfonate was soluble only in DMF and DMSO. Received: 18 October 1996/Revised: 8 November 1996/Accepted: 15 November 1996     

Molecular weight determination of HTPB resins by vapor pressure osmometry (VPO) and gel permeation chromatography (GPC): The effect of calibration standards

GPC and VPO behaviours of HTPB samples have been examined in toluene employing polystyrene and polybutadiene standards. The results show that the molecular weights obtained depend on the nature of the calibration standards, particularly in the GPC analysis. Received: 7 October 1996/Revised: 19 December 1996/Accepted: 23 December 1996     

Miscibility of polysulfone and poly(ether sulfone) with tertiary amide polymers

The miscibility of polysulfone (PSf) and poly(ether sulfone) (PES) with three tertiary amide polymers has been studied. PES is miscible with poly(N-methyl-N-vinylacetamide) (PMVAc) and with poly(N,N-dimethylacrylamide) (PDMA) but not with poly(2-methyl-2-oxazoline) (PMOx). Miscible PES/PDMA blends show lower critical solution temperature behavior. However, PSf is immiscible with all the three tertiary amide polymers. Previous studies have shown that both PES and PSf are miscible with poly(N-vinyl-2-pyrrolidone). PES is also miscible with poly(2-ethyl-2-oxazoline) but PSf is not. Therefore, PES is more readily miscible with tertiary amide polymers as compared to PSf. Received: 23 October 1996/Revised: 11 November 1996/Accepted: 12 November 1996     

Effect of the crosslinking with 1,1,1-trimethylolpropane trimethacrylate on 5-fluorouracil release from poly(2-hydroxyethyl methacrylate) hydrogels

The aim of this study is to examine the influence of crosslinking density on 5-Fluorouracil release from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels crosslinked with 1,1,1-trimethylolpropane trimethacrylate (TPT). PHEMA hydrogels were synthesized by bulk polymerization with different proportions of TPT (1 – 10 wt%) as crosslinker agent and ammonium persulphate as initiator, enabling polymerization in the feed mixture in the presence of water. As a result, 5-FU could be trapped by including it as a sodium salt in the feed mixture of polymerization. Discs with 5-FU loads between 1 – 16 mg/disc were obtained. Swelling and 5-FU release kinetics studies were carried out in saline solution at 310 K. The diffusion studies were in accordance with Fick's second law during the initial stages, enabling the diffusion coefficients of the process to be determined. The time required for discs to reach total 5-FU release was between 35 h and 160 h and was a function of crosslinking density of the gels and 5-FU load of the discs. Received: 12 July 1996/Revised version: 8 October 1996/Accepted: 15 October 1996     

Electrical conductivity of polystyrene/styrene-butadiene block copolymer blends containing carbon black

The electrical resistivity and mechanical properties of carbon black (CB)-filled polystyrene (PS)/styrene-butadiene block copolymer (SB) blends have been studied. Good electrical performance was achieved with pure SB and PS/SB blends indicating an inhomogeneity of these materials and the heterogeneous micro-dispersion of the CB particles. The percolation threshold of the filler inside SB or PS/SB blends is around 3.6 wt%, which is lower than that expected for incompatible PS/PBD blend. The addition of small amount CB decreases the elongation at break of PS/SB blends indicating some disturbance at the interface of these compatible material. Received: 28 July 1996/Revised version: 1 October 1996/Accepted: 3 October 1996     

Synthesis and characterization of novel well-defined stars consisting of eight polyisobutylene arms emanating from an octa(dimethylsiloxy)octasilsesquioxane core

The synthesis and characterization of novel stars, octa(polyisobutylenedimethylsiloxy)octasilesquioxane (T₈ ^DPIB), consisting of eight polyisobutylene arms emanating from an octa(dimethylsiloxy)octasilsesquioxane (T₈ ^D) core are described. The synthesis involves: 1) The synthesis of allyl-terminated polyisobutylene (PIB^█01█) prearms, 2) The synthesis of octa(hydrodimethylsiloxy)octasilsesquioxane (T₈ ^DH) precore and 3) Star formation by hydrosilation of PIB^█01█ with T₈ ^DH. Conditions for the precision synthesis and characterization of well-defined octa-arm stars are described. Received: 13 September 1996/Accepted: 14 October 1996     

Photoinitiated cationic ring-opening polymerization of a cyclosiloxane

Hexamethylcyclotrisiloxane was found to undergo photoinitiated cationic ring-opening polymerization in solution and bulk, upon exposure to UV radiation, in the presence of either sulfonium or iodonium salts or an iminosulfonate derivative. Glass transition temperatures were below − 100 °C. Molecular weights, determined by size exclusion chromatography relative to polystyrene standards, increased with photolysis lamp intensity. Use of an iodonium photoinitiator afforded poly(dimethylsiloxane) with Mn = 172,000. Polymerization of hexamethylcyclotrisiloxane was accompanied by a small increase in volume (3 – 4%). Received: 12 September 1996/Revised: 29 October 1996/Accepted: 1 November 1996     

Crystallization of syndiotactic polypropylene (sPP) from oriented melts

The influence of the syndiotacticity on the crystallization behaviour of syndiotactic polypropylene (sPP) has been investigated. The syndiotacticity has been measured by ¹³C-NMR spectroscopy and the phase information has been observed by electron diffraction of oriented samples. It is shown that the crystal phase formation depends strongly on the perfection of the tacticity of the macromolecules. Received: 4 November 1996/Revised: 27 November 1996/Accepted: 27 November 1996     

Effect of surfactant concentration, pH, and shear rate on the rheological properties of aqueous systems of a hydrophobically modifed chitosan and its unmodified analogue

Oscillatory shear, shear relaxation and viscosity experiments have been carried out on semidilute solutions of chitosan and on a hydrophobically modified analogue (HM-chitosan) in 1% acetic acid. This was done in the presence of various amounts of cetyltrimethylammonium bromide (CTAB) and at different pH values. All the rheological measurements on the HM-chitosan solutions revealed significant polymer-surfactant interaction and pH effects. The observed rheological effects were least pronounced at pH ≈ 4, while a strong viscoelastic response was found at pH values of 1 and 5 in HM-chitosan solutions of low surfactant concentration. At these conditions, significant shear-thinning effects were observed. In semidilute solutions of unmodified chitosan, the influence of pH, surfactant concentration and shear rate on the rheological properties was moderate or insignificant. Received: 25 September 1996/Revised version: 30 October 1996/Accepted: 4 November 1996     

Synthesis and characterization of polysulfone–poly(alkylene oxide) block copolymers containing poly(dimethylsiloxane)

Block copolymers of polysulfone–poly(alkylene oxide)–poly(dimethylsiloxane) have been prepared by the addition of preformed α,ω-bis(hydrogensilyl)poly(dimethylsiloxane) oligomers to allyl end-capped poly(alkylene oxide)–polysulfone. The hydrosilylation reaction, catalyzed by platinum, was employed for incorporation of the siloxane chain into the copolymers in a 1 : 1 or 1 : 2 molar ratio of Si–H-terminated polydimethylsiloxane to allyl end-capped polysulfone. The products were characterized by IR, ¹H-NMR, and gel permeation chromatography. The thermal stability was determined by thermogravimetric analysis. Differential scanning calorimetry was used to investigate microphase separation in the block copolymers. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of vinyl silane modified imidazole copolymer as a novel corrosion inhibitor

For a novel corrosion inhibitor for copper, the free radical copolymerization of vinyl imidazole (VI) and vinyl trimethoxy silane (VTS) was carried out in benzene at 68 °C using azobisisobutyronitrile (AIBN) as an initiator. The reactivity ratios of the two monomers were determined from instantaneous composition diagram: r _VI = 3.22 and r _VTS = 0. Thermal stability of poly(VI-co-VTS) depended on VTS mole fraction in the feed rather than the molecular weight of the copolymer, due to the disiloxane bond linkages formed during heating. Received: 21 October 1996/Revised: 9 December 1996/Accepted: 12 December 1996     

Photodegradation of chain halogenated polystyrene: Poly (c-chloro and c-bromostyrene)s

The photodegradation of films of poly chain-chlorostyrene (PCCS) and poly chain-bromostyrene (PCBS) achieved by exposure to 254-nm radiation under dynamic vacuum was studied. The minor gaseous products obtained were hydrogen halides and monomer. The polymers were investigated by ir, gel permeation chromatography, and microanalysis. Both polymers undergo main chain scission. The ir spectra of the degraded polymers indicate the presence of unsaturated species. An initial α-carbon-halogen bond fission is required to account for the present reaction products. Possible mechanism of the various photoreactions are discussed. Received: 26 August 1996/Revised: 12 November 1996/Accepted: 20 November 1996     

Synthesis and free radical polymerization of 4-{1′-(2″-methacryloyloxyethoxy)-5′-naphthyliminomethylidene}-4′-nitrostilbene for nonlinear optical applications

4-{1′-(2″-Methacryloyloxyethoxy)-5′-naphthyliminomethylidene}-4′-nitro-stilbene 6 was prepared by the reactions of methacryloyl chloride with 4-{1′-(2″-hydroxyethoxy)-5′-naphthyliminomethylidene}-4′-nitrostilbene 5. Compound 5 was synthesized from 4′-methyl-4-nitrostilbene by several reaction steps. Monomer 6 was polymerized with DTBP as a radical initiator to obtain polymer with 4-(1′-oxy-5′-naphthyliminomethylidene)-4′-nitrostilbene, which is presumably effective chromophore for second-order nonlinear optical applications in the side chain. The resulting polymethacrylate 7 showed a thermal stability up to 300 °C in TGA thermogram, and the T_g value obtained from DSC thermogram was 120 °C, which is acceptable for NLO device applications. Received: 14 October 1996/Accepted: 11 December 1996     

Concentration effects during the formation of poly (acrylic acid)-metal complexes in aqueous solutions

Summary The formation of metal complexes between poly (acrylic acid) and divalent, trivalent and tetravalent metal ions was studied. For divalent metal ions, the formation constants determined according to the method of Gregor et al. strongly decrease with increasing ligand concentration in the range 25–280 mM but are nearly insensitive to the ligand to metal concentration ratio. The metal ions were divided in four groups depending on their effect on the pH decrease of the solution. These groups differ from one another by i) the speed of water exchange or ii) by the speed of ligand exchange in the coordination sphere of the metal. The increase of the ligand concentration or of the ligand to metal ratio always led to an increase of the exchange speed of both water and carboxyl groups. Received: 7 August 2000/Revised version: 15 October/Accepted: 15 October 2000     

Cirality induction in liquid crystalline side-chain polyethers prepared by copolymerization of oxiranes with mesogenic and non mesogenic groups

Copolymers prepared by anionic initiation from racemic or optically active styrene oxide and a racemic oxirane bearing cyanobiphenyl mesogenic group in the side chain are liquid crystalline when the content of the mesogenic monomer exceeds 60 mole %. Copolymers prepared from a mesogenic oxirane with a short spacer and racemic styrene oxide exhibit a nematic phase, while those prepared with optically active styrene oxide exhibit a cholesteric phase, thus indicating a transfer of chirality from the main chain towards the mesophase. Such a transfer of chirality is no more observed in the case of a copolymer prepared from a mesogenic oxirane with a long spacer. Received: 18 October 1996/Revised: 18 November 1996/Accepted: 20 November 1996     

An alternating copolymer for a blue light-emitting diode

An alternating copolymer composed of 9,9′-dihexylfluorene and N-2-ethylhexyl carbazole was synthesized to use as an emissive polymer in a light-emitting diode (LED). The copolymer is soluble in organic solvents and spin-cast to make a fine film. An LED fabricated by sandwiching the alternating copolymer between indium-tin oxide and aluminum emits a white color with the full width at half maximum of 150 nm. The electroluminescence spectrum becomes simplified to have an emission peak at 460 nm for fine blue color when the copolymer is blended with poly(vinylcarbazole) with a ratio of 1 to 4 before the use as an emissive layer. The forward bias turn-on voltage for the LED is 13, and quantum efficiency is 0.002%. Received: 21 October 1996/Revised: 6 November 1996/Accepted: 19 November 1996     

Polymerization of methyl and phenyl oxazoline initiated with carboxylic acid chlorides

Methyl and phenyl oxazoline were polymerized using carboxylic acid chlorides as initiators. The first step of the reaction was shown to consist in a fast reaction of the carboxylic acid chloride with the oxazoline. Resulting product, which was isolated and identified, act as the proper initiator of the polymerization of the oxazoline, which proceeds via covalent or, when chloride counter ion is replaced with iodide or triflate, ionic active species. Apparent rate constants of the chain growth were determined. When methacryloyl chloride is used as initiator macromonomers are obtained, which were copolymerized with styrene. Macromolecular carboxylic acid chlorides initiate the polymerization of oxazolines, yielding graft polymers. Received: 7 October 1996/Accepted: 15 October 1996