Tetrahydrofuran and 3,3-bis(chloromethyl) oxetane triblock copolymers synthesized by two-end living cationic polymerization

Triblock copolymers based on tetrahydrofuran (THF) and 3,3-bis(chloromethyl) oxetane (BCMO), BCMO-block-THF-block-BCMO and poly(BCMO-co-THF)-THF-(BCMO-co-THF), have been synthesized by two-end living cationic polymerization with a bifunctional initiator, trifluoromethanesulfonic anhydride [(CF₃SO₂)₂O]. The polymers are obtained by using the two end propagating species of poly(THF) to initiate the sequential BCMO polymerization. The resulting polymers are characterized by infrared (IR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC), confirming that the polymers are ABA-type block copolymers. The identities of the molecular weights predetermined and which determined by GPC show the success of predetermining molecular weights of the polymers and preparing well-defined polymers. The narrow polydispersities, 1.1–1.3, indicate that the chains are propagating by a living mechanism. © 1993 John Wiley & Sons, Inc.     

Cationic ring-opening polymerization of oxetane derivatives initiated by superacids: Studies on their propagating mechanism and species by means of 19F-NMR

The nature of ring-opening polymerization of oxetane derivatives initiated by triflic acid and triflic anhydride was investigated via ¹⁹F-NMR spectroscopy. Two types of propagating species, which were directly observed from the ¹⁹F-NMR spectra, were found to be oxonium macroions and triflic macroesters. These two propagating species established and equilibrium relationship during the polymerization process. The forming of oxonium macroion active species was highly dependent upon the substituents of the oxetane ring, and were enhanced when a more polar solvent was employed. The initiator effect, which occurred primarily in the initiating stage of the polymerization, is also discussed. © 1994 John Wiley & Sons, Inc.     

Synthesis of polyesters by the polyaddition of bis(oxetane)s with active di(ester)s

The polyaddition of bis(oxetane)s 1,4‐bis[(3‐ethyl‐3‐oxetanylmethoxymethyl)]benzene (BEOB), 4,4′‐bis[(3‐ethyl‐3‐oxetanyl)methoxy]benzene (4,4′‐BEOBP), 1,4‐bis[(3‐ethy‐3‐oxetanyl)methoxy] ‐benzene (1,4‐BEOMB), 1,2‐bis[(3‐ethyl‐3‐oxetanyl)methoxy]benzene (1,2‐BEOMB), 4,4‐bis[(3‐ethyl‐3‐oxetanyl)methoxy]biphenyl (4,4′‐BEOMB), 3,3′,5,5′‐tetramethyl‐[4,4′‐bis(3‐ethyl‐3‐oxetanyl)methoxy]biphenyl (TM‐BEOBP) with active diesters di‐s‐phenylthioterephthalate (PTTP), di‐s‐phenylthioisoterephthalate (PTIP), 4,4′‐di(p‐nitrophenyl)terephthalate (NPTP), 4,4′‐di(p‐nitrophenyl)isoterephthalate (NPIP) were carried out in the presence of tetraphenylphosphonium chloride (TPPC) as a catalyst in NMP for 24 h, affording corresponding polyesters with M_n's in the range 2200–18,200 in 41–98% yields. The obtained polymers would soluble in common organic solvents and had high thermal stabilities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1528–1536, 2004     

神奇的手性螺环配体

过渡金属参与的不对称催化反应是有机合成化学研究的前沿和热点. 寻找和发现新颖配体骨架并开展新型高效的手性配体及催化剂的设计合成是不对称催化反应研究的核心内容. 从20世纪90年代,特别是进入21世纪以来,螺环骨架手性配体受到了广泛的关注,并逐渐发展成为特色鲜明的手性配体类别. 手性螺环配体的骨架已由多手性的螺[4.4]壬烷骨架发展到只具有单一手性的螺二氢茚和螺[4.4]壬二烯等螺环骨架类型,形成了包括手性螺环单磷配体、双膦配体、膦氮配体、双氮配体等丰富的手性配体库. 这些手性螺环配体及其催化剂不仅在不对称催化氢化、不对称碳―碳键形成、不对称碳―杂原子键形成等多种类型的不对称催化反应中均表现出优异的催化活性和对映选择性,且使得许多原先难以控制对映选择性的不对称催化反应变得可能. 而今,手性螺环结构已成为“优势结构”,相应的手性螺环配体及其催化剂已被国内外同行广泛采用. 手性螺环配体的兴起为手性催化剂研究增加了活力,极大地促进了不对称合成化学的发展. 今后,手性螺环配体的研究除了将向新型、高效、高选择性手性配体及催化剂方向发展外,将其应用于新的不对称催化反应的对映选择性控制、以及应用于手性天然产物和药物的高效不对称合成将成为新的研究热点.     

Crystallization kinetics of the monoclinic modification of poly(3,3-dimethyl oxetane)

Poly(3,3-dimethyl oxetane) fractions ranging in number average molecular weights from 18500 to 130000 have been isothermally crystallized from the relaxed melt state in the temperature range from 12 to 44 °C, where only the monoclinic modification is formed. The influence of molecular weight and undercooling in crystallization kinetics has been analyzed. The level of crystallinity is very slightly dependent on molecular weight but the influence of this parameter on the time scale of the crystallization is relatively pronounced. The crystallization temperature coefficient was determined and it was found a constant value of the product of the interfacial energies in the range of molecular weights which has been analyzed. Growth rate measurements were carried out for fraction ¯M _n=130000 and it was found that the temperature coefficients for overall and growth rates are equal. Finally, the comparison of the experimental results for this polymer with those reported for poly(oxetane) shows two main differences: first, the crystallization rate is slower for poly(3,3-dimethyl oxetane) and second, the temperature coefficient is smaller for this polymer.     

Effect of molecular weight and temperature on the isothermal crystallization of poly(oxetane)

Poly(oxetane) fractions ranging in number-average molecular weights from 7800 to 157000 have been isothermally crystallized in the temperature range from –50 to 19 C, using dilatometric and calorimetric techniques. In both cases, reproducible isotherms were obtained with an Avrami exponent equal to three. The crystallization rate against crystallization temperature presents a maximum at –30 C. The level of crystallinity changes with molecular weight and the influence of this parameter on the rate of crystallization is pronounced. The crystallization temperature coefficient was studied using nucleation theory and it was found an slight increase in the basal interfacial free energy for the lowest molecular weight fraction. For the analysis of the temperature coefficient at the higher undercoolings, different approximations for the free energy of fusion and the transport term have been considered. The conclusion of this analysis is that, independently of these approximations, the obtained temperature coefficients are the same.     

Synthesis of new monofunctional and oligofunctional oxetane acetals

Derivatives of 3‐ethyl‐3‐(hydroxymethyl)oxetane (trimethylolpropane oxetane), potentially useful in cationic UV‐curable formulations, were prepared by the simple acid‐catalyzed addition of alcohols to 1‐alkenyl ethers. Examples include several difunctional oxetane derivatives along with one fluorinated and one acryloylated oxetane derivative. These new materials may find use as reactive diluents or binders in several applications. A preliminary assessment of the curing was made. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 613–619, 2001     

Tri‐block copolymers of polyethylene glycol and hyperbranched poly‐3‐ethyl‐3‐(hydroxymethyl)oxetane through cationic ring opening polymerization

Tri‐block copolymers of linear poly(ethylene glycol) (PEG) and hyperbranched poly‐3‐ethyl‐3‐(hydroxymethyl)oxetane (poly‐TMPO) are reported. The novel dumb‐bell shaped polyethers were synthesized in bulk with cationic ringopening polymerization utilizing BF₃OEt₂ as initiator, via drop‐wise addition of the oxetane monomer. The thermal properties of the materials were successfully tuned by varying the amount of poly‐TMPO attached to the PEG‐chains, ranging from a melting point of 54 °C and a degree of crystallinity of 76% for pure PEG, to a melting point of 35 °C and a degree of crystallinity of 12% for the polyether copolymer having an average of 14 TMPO units per PEG chain. The materials are of relatively low polydispersity, with M_n/M_w ranging from 1.2 to 1.4. The materials have been evaluated for usage with the energetic oxidizer ammonium dinitramide. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6191–6200, 2009     

Atom transfer radical polymerization of methyl methacrylate catalyzed by ion exchange resin immobilized Co(II) hybrid catalyst

Ion exchange resin immobilized Co(II) catalyst with a small amount of soluble CuCl₂/Me₆TREN catalyst was successfully applied to atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in DMF. Using this catalyst, a high conversion of MMA (>90%) was achieved. And poly(methyl methacrylate) (PMMA) with predicted molecular weight and narrow molecular weight distribution (M_w/M_n = 1.09–1.42) was obtained. The immobilized catalyst can be easily separated from the polymerization system by simple centrifugation after polymerization, resulting in the concentration of transition metal residues in polymer product was as low as 10 ppm. Both main catalytic activity and good controllability over the polymerization were retained by the recycled catalyst without any regeneration process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1416–1426, 2008     

Reactivity of oxetane monomers in photoinitiated cationic polymerization

Studies of the onium salt photoinitiated cationic ring‐opening polymerizations of various 3,3‐disubstituted oxetane monomers have been conducted with real‐time infrared spectroscopy and optical pyrometry. The polymerizations of these monomers are typified by an extended induction period that has been attributed to the presence of a long‐lived tertiary oxonium ion intermediate formed by the reaction of the initially formed secondary oxonium ion with the cyclic ether monomer. Because the extended induction period in the photopolymerization of these monomers renders oxetane monomers of limited value for many applications, methods have been sought for its minimization or elimination. Three general methods have been found effective in markedly shortening the induction period: (1) carrying out the photopolymerizations at higher temperatures, (2) copolymerizing with more reactive epoxide monomers, and (3) using free‐radical photoinitiators as synergists. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3205–3220, 2005     

Copolymerization of carbon dioxide and oxetane catalyzed by aluminum porphyrin complex system

Tetraphenylporphinatoaluminum chloride ([TPP]AlCl) catalyst and tetra-n-butylammonium bromide (TBAB) cocatalyst system is effective for the copolymerization of CO₂ and oxetane even under low CO₂ pressure (~2 MPa). In the presence of toluene as a solvent, poly(trimethylene carbonate) (PTMC) containing >99% of carbonate linkages with M_n = 8600 and M_w/M_n = 1.70 was synthesized. This is the first report of PTMC formation with excellent ratio of carbonate linkages from oxetane and CO₂. According to the kinetic analysis, proton nuclear magnetic resonance (¹H NMR) and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) measurements of the products, PTMC was mainly synthesized via (i) the trimethylene carbonate (TMC) formation from CO₂ and oxetane and (ii) the successive ring-opening polymerization of TMC.     

手性螺环配体的合成及其在不对称催化反应中的应用研究进展

手性螺环配体的合成及其在不对称催化反应中的应用是不对称合成和催化研究中重要的研究领域之一, 一些手性螺环配体被合成出来并成功地应用于不对称催化反应中. 综述了近十年来手性螺环配体的合成及在不对称催化反应中的应用研究进展.     

Synthesis of polyphosphonates containing pendant chloromethyl groups by the polyaddition of bis(oxetane)s with phosphonic dichlorides

The polyaddition of 4,4′‐bis[(3‐ethyl‐3‐oxetanyl)methoxy]biphenyl (4,4′‐BEOBP) and phenylphosphonic dichloride (PPDC) with quaternary onium salts as catalysts proceeded under mild reaction conditions to afford a polymer containing phosphorous atoms in its main chain. A polyphosphonate with a high number‐average molecular weight (10,300) was obtained by the reaction of 4,4′‐BEOBP and PPDC in the presence of tetraphenylphosphonium chloride (TPPC) in o‐dichlorobenzene at 130 °C for 24 h. The structure of the resulting polymer was confirmed with IR, ¹H NMR, and ³¹P NMR spectroscopy. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with phosphonic dichlorides proceeded smoothly to give corresponding polyphosphonates with TPPC as the catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3835–3846, 2002     

A novel synthesis of polyethers with pendant hydroxyl groups by polyaddition of bis(oxetane)s with bis(phenol)s

The polyaddition of 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene (BEOB) with 3,3′,5,5′-tetrachlorobisphenol A (TCBPA) was examined with or without catalysts. High molecular weight polymer (polymers 1) (M_n = 13,600) with pendant primary hydroxyl groups was obtained in a 99% yield without any gel products when the reaction was performed with 5 mol % of tetraphenylphosphonium bromide as a catalyst in NMP at 160°C for 96 h. However, when the reaction was carried out without a catalyst under the same conditions, a low molecular weight polymer (M_n = 3200) was obtained in a 51% yield. The structure of the resulting polymer was confirmed by IR, ¹H-NMR, and ¹³C-NMR spectra. In this reaction system, it was also found that tetraphenylphosphonium iodide and crown ether complexes such as 18-crown-6 (18-C-6)/KBr and 18-C-6/KI have high catalytic activity. Polyadditions of 1,4-bis[(3-methyl-3-oxetanyl)methoxymethyl]benzene with TCBPA and BEOB with 3,3′,5,5′-tetrabromobisphenol-S were also examined, and corresponding polymers (polymers 2 and 3) were obtained in good yields. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2781–2790, 1999     

Osmium(VIII) catalyzed oxidation of tellurium(IV) by periodate in aqueous alkaline medium

Osmium(VIII) catalyzed oxidation of tellurium(IV) by periodate in alkaline medium is found to occurvia oxidant-catalyst complex formation in a slow step followed by the interaction of substrate and complex in the fast step to yield the products with regeneration of catalyst. One of the products, Te(VI), considerably retards the rate of reaction. The reaction shows zero order in [tellurium(IV)], first order each in [IO₄] and [Os(VIII)] and an inverse fractional order dependence on [OH]. A plausible mechanism is proposed and the reaction constants involved in the mechanism are derived.     

Antibacterial poly(ethylene terephthalate) surfaces obtained from thymyl methacrylate polymerization

Thymol, an antibacterial agent was used for the preparation of a methacrylic monomer. The conventional and atom transfer radical (ATRP) polymerizations of this monomer were studied using different conditions. Then, the functionalization of poly(ethylene terephthalate) (PET) films by “grafting from” ATRP using this monomer was investigated. In this aim, a three steps procedure was developed. The surfaces were first treated by NH₃ plasma treatment to incorporate primary amino functions. Then, in a second step, ATRP initiator was grafted by reaction with bromoisobutyryl bromide. Surface initiated ATRP of thymyl methacrylate was performed in solution in the presence of a sacrificial initiator. The efficiency of these reactions was confirmed by X‐ray photoelectron spectroscopy. Wetting properties and surface energy were found to vary systematically depending to the type of functionalization and grafting. The poly(thymyl methacrylate)‐grafted PET surfaces exhibit resistance to bacterial adhesion toward Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus strains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1975–1985     

Iron(III) porphyrin catalyzed ionic liquid mediated polymerization of methylmethacrylate

A novel application of iron(III)porphyrin catalyst, 5,10,15,20 ? tetrakis ? (2′,6′‐dichlorophenyl)porphyrinatoiron(III) chloride is reported for the reaction of methyl methacrylate with hydrogen peroxide in imidazolium ionic liquids at ambient temperature. The reaction furnished polymethyl methacrylate in 75–94% yields. The yield of the polymer was optimized upon changing the reaction media, ratio of catalyst, oxidant and substrate, reaction time and quenchers. The polymethyl methacrylate was secured as highly stereoregular with predominantly syndiotactic sequences as analyzed with the aid of NMR (¹H and ¹³C) and infrared spectroscopy. Besides, the number‐average molecular weights (Mn) were attained in the range of 15,000 to 55,000 with narrow polydispersity (~1.1–1.9) as calculated using gel permeable chromatography (GPC).     

Anionic ring-opening polymerization of silacyclobutane derivatives

Anionic polymerizations of 1,1-dimethylsilacyclobutane, 1,1-diethylsilacyclobutane and 1-methyl-1-phenylsilacyclobutane were investigated. Addition of 5 mol % of butyllithium to a solution of 1,1-dimethylsilacyclobutane in THF-hexane (1 : 1) at −48°C provided poly(1,1-dimethylsilabutane) in 99% yield. M_n and M_w/M_n of the obtained polymer were 2400 and 1.10. This polymerization proceeded with a living nature. M_n increased in proportion as the yield of polymer increased. Addition of the second fresh feed of the monomer to the reaction mixture restarted polymerization of the second monomer at the same rate as in the initial stage. Addition of styrene to the living poly(1,1-dimethylsilabutane) provided a poly(1,1-dimethylsilabutane-b-styrene) block copolymer. It was also found that a polymerization of 1,1-diethylsilacyclobutane in THF-hexane at −48°C showed a living nature. In contrast, a polymerization of 1-methyl-1-phenylsilacyclobutane in THF at −78°C did not show a living nature. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3207–3216, 1997