Asymmetric polymerization of N-substituted maleimides with organolithium — bisoxazolines complex

Asymmetric anionic polymerizations of achiral N-substituted maleimide (RMI) (N-cyclohexyl (CHMI), N-phenyl (PhMI), N-tert-butyl (TBMI)) by n-butyllithium (n-BuLi) or fluorenyllithium (FlLi) complexes of chiral bisoxazoline derivatives in toluene gave optically active polymers ([α]²⁵ ₄₃₅− 2.9° to − 8.2°). The polymers prerared with initiator of n-BuLi – 2,2′-bis(4,4′-isopropyl-,3-oxazoline) showed negative specific rotations (poly(RMI), [α]²⁵ ₄₃₅− 5.8° to − 8.2°) which were greater than those ([α]²⁵ ₄₃₅− 2.9° to − 5.9°) with other chiral 2,2′-bis(4,4′-alkyl-1,3-oxazoline) (alkyl group = iso-butyl and benzyl). Received: 29 July 1997/Revised: 27 August 1997/Accepted: 1 September 1997     

Synthesis,characterization and acidochromism of Poly (2-<Emphasis Type="Italic">N,N</Emphasis>–dimethylamino-4,6-Bis (2-thienyl)-pyrimidine)

A new monomer (2-N,N-dimethylamino-4,6-Bis (2-thienyl)–pyrimidine) was synthesized and its homopolymer was successfully prepared by using Ferric trichloride (FeCl₃) as an oxidant. The structure of the polymer and monomer was fully characterized by ¹H–NMR, FTIR, UV-vis, Fluorescent spectroscopy and X-ray diffraction pattern. The polymer gives rise to a band at λ _max = 391 nm. The polymer showed the PL spectrum, gave a peak at 507 nm.We have observed that the polymer was sensitive to inorganic acids and the acidochromism behavior was investigated applying organic acid such as CF₃COOH. The corresponding UV-Vis peaks were observed at 464 nm and 357 nm respectively. X-ray diffraction data shows that polymer has a certain crystallinity. The polymer exhibited an [η] value of 0.26 dLg⁻¹ at 25 °C in H₂SO₄ (w = 98%).     

Ring-opening polymerization of γ-glycidoxypropyltrimethoxysilane catalyzed by multi-metal cyanide catalyst

Ring-opening polymerizations of γ-glycidoxypropyltrimethoxysilane (GPTMS) were carried out by using multi-metal cyanide (MMC) catalyst and the synthesized homopolymer was a comb-shaped polymer with regular structure. The structure of the polymer obtained (P-GPTMS) was characterized by FTIR, ¹H-NMR, and ²⁹Si-NMR spectroscopy, and the molecular weight and its distribution were analyzed by size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS). The thermal behavior of P-GPTMS was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). P-GPTMS with high molecular weight (M _n = 18,000–80,000) and narrow molecular weight distribution (1.10–1.35) were synthesized when the dosage of MMC catalyst was 0.1% and polymerization temperature was 130 °C. The molecular weight of the product could be adjusted by controlling the polymerization time. The T _g of P-GPTMS is in the range of −34 to −30 °C. On the basis of the TGA data, the decomposition rate of P-GPTMS reached its peak at 374.14 °C and the entire decomposition stopped at 600 °C.     

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate)-mediated RAFT polymerization of N-vinylpyrrolidone

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly synthesized (S)-2-(ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the reversible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of N-vinylpyrrolidone (NVP). The former showed the better chain transfer ability in the polymerization at 60 °C. Kinetics study with X1 shows the psuedo-first order kinetics upto 45% monomer conversion. Molecular weight (M _n) of the resulted polymer increases linearly with increase in the monomer conversion upto around 45%. Polydispersity of the corresponding poly(NVP)s increase gradually from 1.2 to 1.9 with increase in the monomer conversion. Chain-end analysis of the resulted polymer by ¹H NMR shows clearly that polymerization started with radical forming out of xanthate mediator. Living nature of the polymerization was confirmed from the successful homo chain extension experiment and also the hetero-chain extension experiment involving synthesis of poly(NVP)-b-polystyrene amphiphilic diblock copolymer.     

Synthesis and polymerization of 3-(t-butoxycarbonyl)-1-vinylcaprolactam and application as deep UV resists

Poly(3-(t-butoxycarbonyl)-1-vinylcaprolactam) (PBCVC) was synthesized and evaluated as a potential deep UV photoresist. The synthesized polymer has excellent transmittance at 248 nm (absorbance = 0.018 μm⁻¹). In addition, PBCVC possesses good thermal stability up to 220 °C and a high glass transition temperature (174 ∼ 190 °C). The thermal deprotection of side chain ester groups of PBCVC occurs at 220 °C, whereas in the presence of acid the cleavage of the t-butyl ester groups of PBCVC begins at about 80 °C, and followed by evolution of carbon dioxide at about 150 °C. Deprotection of PBCVC gave the corresponding polymer, poly(1-vinylcaprolactam-3-carboxylic acid). The contrast of the PBCVC resist system was not deteriorated with the post-exposure delay (PED) time. Received: 2 September 1996/Revised: 18 December 1996/Accepted: 20 December 1996     

Synthesis and polymerisation of maleoyl-L-histidine monomers and addition of histidine to an ethylene-alt-maleic co-polymer

This work has investigated two routes of synthesising polymers containing L-histidine using maleimide chemistry; grafting of histidine onto an ethylene-alt-maleic anhydride copolymer and AIBN (azobisisobutyronitrile) initiated radical polymerisation of the monomer maleoyl-L-histidine. The grafting technique and monomer synthesis are utilising the maleimide formation between the primary amine of histidine and maleic anhydride. The reactions are conveniently carried out in one step with good yields. The copolymers containing L-histidine were prepared by reacting L-histidine or L-histidine methyl ester with poly(ethylene-alt maleic anhydride) in DMSO at 50 °C for 8–16 h with 80% yields independent of the degree of substitution. The monomer maleoyl-L-histidine was synthesised by reacting histidine and maleic anhydride in acetic acid and the monomer was subsequently polymerised by AIBN radical initiation in DMSO at 80 °C for 48 h to yield poly(N-histidyl maleimide). The resulting polymer had a different optical rotation ([α]_D²⁰ = −11) than the monomer ([α]_D²⁰ = +25), which is ascribed to the threo-diisotactic and/or threo-disyndiotactic stereoregularity of the polymer.     

Multi-arm star-branched polyisobutylene ionomers

A series of multi-arm star-branched polyisobutylenes was synthesized via living carbocationic polymerization. Arms with molecular weights ranging from 10,000 to 30,000 g/mol were prepared using the cumyl chloride/TiCl₄/pyridine initiation system in 60/40 (v/v) hexane/methyl chloride at − 80 °C and linked by sequential addition of divinylbenzene. The weight average number of arms per star polymer, N _w, scaled inversely with arm molecular weight and ranged from 32 to 5. Star-telechelic ionomers were produced by sulfonation of the aromatic initiator residue at the end of each arm, followed by neutralization. Sulfonation was quantitative as indicated by acid-base titration. Potassium ionomers were elastic solids which were marginally soluble in THF; the precursors were tacky and freely soluble in THF. Ionic modification did not alter the glass transition temperature (− 66 °C), but the thermal decomposition temperature in N₂ was increased from 375 to 400 °C. Received: 25 July 1997/Accepted: 27 August 1997     

Synthesis of poly(N,N-dimethylcarbamoylmethylene) as a polymer homolog of N,N-dimethylacetamide

Summary A novel polymer homolog of N,N-dimethylacetamide (DMAc) having amide groups on all main chain carbons, poly(N,N-dimethylcarbamoylmethylene) 1, was prepared by heating poly(di-t-butyl fumarate) 2 at 180 °C for 2 hours followed by treatment with hexamethylphosphoramide at 180 °C for 5 hours. The structure of the obtained polymer 1 was confirmed by ¹H-, ¹³C-NMR and IR spectroscopy. The polymer 1 actually showed the properties based on its repeating structures. 1 had the amphiphilicity and was soluble both in protic and aprotic solvents. Furthermore, 1 showed the miscibility with commodity polymers such as poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(vinyl chloride). In comparison with another polymer homolog of DMAc, poly(2-methyl-2-oxazoline), the polymer 1 exhibited better miscibility with poly(N-vinylpyrrolidone). Received: 24 June 1999/Accepted: 19 July 1999     

Free Radical Polymerisation of Methylmethacrylate Using p-nitrobenzyltriphenyl Phosphonium Ylide as Novel Initiator

p-nitrobenzyl triphenyl phosphonium ylide initiated radical polymerisation of MMA in 1-4 dioxane at 65 ± 1°C for 2 h under a nitrogen blanket, follows ideal kinetics with bimolecular termination. The overall activation energy and average value of k _p ²/k _t are 75.7 kJ mol and 1.14 × 10² l mol⁻¹ s⁻¹. FTIR Spectroscopy confirms a band of 1,729 cm⁻¹ of the ester group. ¹H NMR and ¹³C NMR confirms methoxy protons at 3.8 δ ppm and 52 δ ppm, respectively. E.S.R studies confirm a free radical mode of polymerisation. TGDTA analysis confirms the atactic nature of polymer and its thermal stability up to 120°C. Ylide dissociates to give a phenyl radical which is responsible for polymerisation.     

NO2 Reduction with Nitromethane over Ag/Y: A Catalyst with High Activity over a Wide Temperature Range

Nitromethane (NM) is a very efficient reductant for converting NO₂ to N₂ over Ag/Y: Between 140 °C and 400 °C, the N₂ yield is close to 100%. This high N₂ yield results from the ability of Ag/Y to effectively catalyze the reaction between NM and NO₂. This high catalytic activity of Ag/Y is minimally affected by surface bound CN⁻, NC⁻, or acetate, all of which are stable at temperatures below ∼300 °C. At T ≥ 400 °C, there is a reaction path that yields N₂ from NM even in the absence of NO₂. However even at 400 °C, under typical deNO _x conditions, most N₂ molecules are formed as a result of the reaction of NM and NO₂.     

Antiinflammatory polymer-bound steroids for topical applications. I. Synthesis and characterization

Covalent binding of hydrocortisone and dexamethasone to hydrophylic biocompatible macromolecular carriers through hydrolizable carbonate linkage was investigated according to two complementary strategies. (a) Radical copolymerization of hydrocortisone-²¹C-vinylcarbonate with N-vinylpyrrolidone (NVP,60°C), or N-[tris(hydroxymethyl)methyl]acrylamide (THMMA, 50°C) in dimethylacetamide solution: In spite of a nearly zero reactivity ratio for the steroid monomer which behaves as a degradative transfer agent—C_T ～ 5.7 × 10^?2 and 6.8 × 10^?3 for NVP and THMMA, respectively–this process may afford fairly high molecular weight polymers (M?_w ? 10⁴–10⁵) with high enough hydrocortisone content (0.03–0.10 mole.fraction). (b) Condensation of the hydrocortisone or dexamethasone-²¹C-chloroformates onto poly(oxyethylene glycol) (M?_n = 6220) or hydroxypropylcellulose (HPC, M?_w = 1.35 × 10⁵) in tetrahydrofuran solution (30°C): This straightforward process is of low efficiency (yields >50%), and only HPC derivatives show good chemical homogeneity.     

Kinetics for free radical solution polymerization of heptadecafluorodecyl (meth)acrylate in supercritical carbon dioxide

Free radical solution polymerization of heptadecafluorodecyl acrylate (HDFDA) and heptadecafluorodecyl methacrylate (HDFDMA) was carried out by using 2,2′-azobisisobutyronitrile (AIBN) as the initiator in supercritical carbon dioxide (scCO₂). We performed solution polymerization with changing initiator concentration, temperature and polymerization time to study the polymerization kinetics. A nonlinear least square method and dead-end theory were used to determine the constant, K (K=(k _p √f)/√k _d k _d ) and initiator decomposition rate constant (k _d ) from experimental data. k _d was measured as 3.77 × 10⁻⁵ s⁻¹ at 62.7°C for poly(HDFDA) and 2.71 × 10⁻⁵ s⁻¹ at 62.5 °C for poly(HDFDMA), respectively, by nonlinear least square method.     

A kinetic study on autoxidation of α-naphthol-formaldehyde polymer in aqueous alkaline solutions

α-naphthol-formaldehyde polymer having active methylene groups and low average molecular weight of 1,000–2,000 was synthesized and characterized by FT-IR and gel permeation chromatography(GPC). Macroscopic kinetics of autoxidation of the polymer was investigated in an aqueous alkaline solution using UV/Vis spectrophotometry. Autoxidation processes in the presence of oxygen (or air) and hydrogen peroxide were associated with a color change of the solution to blue, which was monitored at 650 nm. The overall reaction rate law, order of the reaction, kinetic rate constants, and a proposed mechanism for the autoxidation reaction were obtained and reported. Infrared spectrophotometry shows that autoxidation takes place via conversion of methylene groups into carbonyls. Furthermore, kinetic data confirms the proposed mechanism for this autoxidation reaction which is of pseudo zero-order with respect to the polymer and first-order to the oxidant. The obtained kinetic rate constants of the autoxidation reaction by air and hydrogen peroxide are 0.0052 ± 7.1 × 10⁻⁴ min⁻¹ and 0.0044 ± 9.7 × 10⁻⁴ min⁻¹ at 25°C, respectively.     

Novel PEO-based solid composite polymer electrolytes with inorganic–organic hybrid polyphosphazene microspheres as fillers

Novel solid-state composite polymer electrolytes based on poly (ethylene oxide) (PEO) by using LiClO₄ as doping salts and inorganic–organic hybrid poly (cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) microspheres as fillers were prepared. Electrochemical and thermal properties of PEO-based polymer electrolytes incorporated with PZS microspheres were studied. Differential scanning calorimetry (DSC) results showed there was a decrease in the glass transition temperature of the electrolytes and the crystallinity of the samples in the presence of the fillers. Maximum ionic conductivity values of 1.2 × 10⁻⁵ S cm⁻¹ at ambient temperature and 7.5 × 10⁻⁴ S cm⁻¹ at 80° were obtained and lithium ion transference number was 0.29. Compared with traditional ceramic fillers such as SiO₂, the addition of PZS microspheres increased the ionic conductivity of the electrolytes slightly and led to remarkable enhancement in the lithium ion transference number.     

Synthesis and characterization of a new NLO-active donor–acceptor-type conjugated polymer derived from 3,4-diphenylthiophene

A new donor–acceptor-type conjugated polymer (P1) carrying 3,4-diphenylthiophene, 2,5-dihexyloxybenzene, and 1,3,4-oxadiazole units was synthesized through multistep reactions. The polymer was prepared using a polyhydrazide precursor route. The polymer has a well-defined structure and exhibits good thermal stability, with a decomposition onset temperature in nitrogen of 300 °C. Cyclic voltammetry experiments revealed that the polymer has low-lying LUMO (−3.68 eV) and high-lying HOMO (−5.78 eV) energy levels. The electrochemical band gap was found to be 2.10 eV. The UV-visible absorption spectrum of the polymer presented a maximum at 373 nm, and it displayed bluish-green fluorescence in dilute chloroform solution. The nonlinear optical properties of the new polymer were investigated at 532 nm using the Z-scan technique with nanosecond laser pulses. The polymer exhibited strong optical limiting behavior due to excited state absorption, which was phenomenologically similar to a three-photon absorption (3PA) process. The 3PA coefficient γ was found to be 7 × 10⁻²² m³/W². The studies show that the new polymer (P1) is a promising material for developing efficient photonic devices.     

Synthesis of Magnetite Nanoparticles with PDLLA Corona

The ring-opening polymerization (ROP) of D,L-lactide (DLLA) initiated by tin(II) 2-ethylhexanoate (Sn(Oct)₂) on the surface-initiated magnetite (Fe₃O₄) nanoparticles was performed at 130 °C. Effects of the polymer molar mass and concentration on the amount of polymer on the surface were investigated. The number average molecular weights, M _n , that we obtained by both nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) methods fit well within the accuracy of the applied methods, and range from 1,100 g · mol⁻¹ to 4,040 g · mol⁻¹. The surface functionalization density for up to 3,900 initiation sites per particle was obtained. The composition of various particles with poly(D,L-lactide) (PDLLA) corona is by means of thermogravimetric analysis (TGA), and indicates magnetite (Fe₃O₄) content between 17 wt.% and 59 wt.%. An erratum to this article can be found at     

Effect of temperature and chainlength on the densities and molal volumes ofn-alkyl chlorides

The densities ofn-alkyl chlorides from pentyl chloride to hexadecyl chloride were determined at temperatures between 15–80°C at 5°C intervals. The densities increase linearly with temperature and chainlength. A four-constant equation, V=n/(−3.6640 × 10⁻⁵ T+0.07151)+1/(−5.6526 × 10⁻⁵ T+0.04243), was formulated. This formula accurately predicted the molal volume and, hence, the density for all then-alkyl chlorides at any temperature within the range.     

Photoinitiated cationic polymerization of epoxide and vinyl monomers by p-trimethoxytrityl salts

Photoinitiated cationic polymerizations of cyclohexene oxide, tetrahydrofuran and N-vinylcarbazole were investigated in dichloromethane at 25°C, using stable, soluble and nonhygroscopic p-trimethoxytrityl salts having nonnucleophilic anions such as SbF₆ ⁻, AsF₆ ⁻, PF₆ ⁻, BF₄ ⁻, and SbCl₆ ⁻. The effects of anion, polymerization time, concentration of the salt and the intensity of light on the polymerization reaction are presented.     

<Emphasis Type="SmallCaps">l</Emphasis>-Aspartic acid incorporated optically active poly(amide-imide)s: synthesis and characterization

N-trimelliticimido-l-aspartic acid (1) was prepared from the reaction of trimellitic anhydride with l-aspartic acid in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. The solution polycondensation of the corresponding activated monomer with eight aromatic diamines were carried out in DMAc. The resulting poly(amide-imide)s were obtained in quantitative yields, showed admirable inherent viscosities (0.20–0.36 dl g⁻¹), good optical activity (+7.32o to +15.24o), and were readily soluble in polar aprotic solvents. They start to decompose (T _10%) above 170 °C and display glass-transition temperatures at 120–237 °C. All of the above polymers were fully characterized by UV, FT–IR, and ¹HNMR spectroscopy, elemental analysis, thermogravimetric analyses, DSC, inherent viscosity measurement, and specific rotation.     

Synthesis and Kinetic Studies on Dimer Fatty Acid/Polyethylene Glycol Polyester

Dimer fatty acid polyethylene glycol polyester, a new kind of non-ionic polymeric surfactant, was synthesized by using dimer fatty acid and polyethylene glycol (400) as materials in this paper. The optimum reaction conditions of esterification were as follows: the molar ratio of dimer fatty acid (DFA)/PEG (400) is 1 / 1.20, the preferable catalyst is stannous chloride and the amount is 0.3% (w/w) of the mass of DFA, reaction temperature is 200°C, reaction time is 6 h. The conversion ratio of polyesterification can reach 98.11%. A new kinetic model of polyesterification reaction catalyzed with stannous chloride was presented. The Genetic Algorithms and Runge–Kutta were used to estimate the parameters of the kinetic model. The results of experiments and computer operations indicated that the reaction order is 0.998 to the carboxyl and 1 order to the hydroxyl. The activation energy obtained from Arrhenius plot is 97.18 kJ mol⁻¹, and the pre-exponential frequency factor is lnA = 21.39 kg² mol⁻² min⁻¹ at temperature range of 160 ∼ 190°C.