Synthesis and characterization of amphiphilic diblock copolymers of methyl tri(ethylene glycol) vinyl ether and isobutyl vinyl ether

Water-soluble diblock copolymers of methyl tri(ethylene glycol) vinyl ether (hydrophilic block) and isobutyl vinyl ether (hydrophobic block) of different molecular weights and composition were synthesized by living cationic polymerization. The molecular weight and comonomer composition of these copolymers were determined by GPC and ¹H NMR spectroscopy, respectively. Aqueous solutions of the copolymers were characterized in terms of their micellar behavior using dynamic light scattering, aqueous GPC, and dye solubilization. All the copolymers formed aggregates with the exception of a diblock copolymer with only two hydrophobic monomer units. The micellar hydrodynamic size scaled with the 0.61 power of the number of hydrophobic units, in good agreement with a theoretical exponent of 0.73. An increase in the length of the hydrophobic block at constant hydrophilic block length or an increase in the overall polymer size at constant block length ratio both resulted in lower critical micelle concentrations (cmcs). The cloud points of 1% w/w aqueous solutions of the polymers were determined by turbidimetry. An increase in the length of the hydrophobic block at constant hydrophilic block length caused a decrease in the cloud points of the copolymers. However, an increase in the overall polymer size at constant block length ratio led to an increase in the cloud point. © 1996 John Wiley & Sons, Inc.     

Enantioselective Addition of Cyclic Enol Silyl Ethers to 2-Alkenoyl-Pyridine-N-Oxides Catalysed by Cu(II) -Bis(oxazoline) Complexes

Asymmetric reactions involving (E)-3-aryl-1-(pyridin-2-yl-N-oxide)prop-2-en-1-ones and cyclic enol silyl ethers show good yields and excellent enantioselectivities (up to 99.9?% ee) when catalysed by bis(oxazoline)-Cu(II) complexes. Different reaction pathways can be followed by different enol silyl ethers: with 2-(trimethylsilyloxy)furan, a Mukaiyama-Michael adduct is obtained, whereas a hetero Diels-Alder cycloadduct was formed by using (1,2-dihydronaphthalen-4-yloxy)trimethylsilane. In the latter reaction, the absolute configuration of the product is consistent with a reagent approach to the less hindered Re face of the coordinated substrate in the reactive complex.     

Synthesis of poly(silyl ether)s via copper-catalyzed dehydrocoupling polymerization

The development of efficient method to prepare poly(silyl ether)s (PSEs) is highly desirable. Herein, an environmentally sustainable copper-catalyzed dehydrocoupling polymerization was developed with good yields and high molecular weight (up to 48,400 of Mn and up to 97% yield). Monomers of different types (AB type or AA and BB type) are suitable to afford PSEs. The PSEs show good thermal stability and low glass-transition temperature.     

Synthesis of poly(vinyl alcohol)-based poly(crown ether)s and permeability of their polymeric membranes

Polymers that contain crown ether moieties at the side chain and are capable of forming rather tough film were synthesized by the polymer reaction of poly(vinyl alcohol) with formyl derivatives of aliphatic crown ethers such as 12-crown-4, 15-crown-5, and 18-crown-6. In the passive transport of alkali metal picrates across the poly(crown ether) membranes the permeation, particularly of alkali metals which tend to form intramolecular sandwich-type complexes with the crown ether rings, was retarded, compared with a poly(vinyl alcohol) membrane. The cation selectivities in the permeation of poly(crown ether) membranes differed significantly from those of poly(vinyl alcohol).     

Near-monodisperse,n-alkyl,end-functionalized poly(methyl vinyl ether)s: Synthesis by living cationic polymerization and solution characterization

Water-soluble amphiphilic diblock copolymers were synthesized by the living cationic polymerization of methyl vinyl ether (hydrophilic block) and its subsequent termination with n-alcohols of chain lengths varying from one to eight, and three n-alkyl carboxylic acids with 10, 12, and 18 carbon atoms. Additionally, water and ethylene glycol were tested as terminating agents. The extent of the functionalization was determined using ¹H NMR spectroscopy. The cloud points of 1% w/w aqueous solutions of the polymers as determined by turbidimetry decreased from 32 to 21°C as the number of carbon atoms of the terminating agent increased. Aqueous GPC revealed micellization of the stearic acid-terminated block copolymer, while the other block copolymers existed mainly as unimers. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2547–2554, 1998     

多磺化侧链型聚芳醚的合成及性能

本文通过对聚合物的结构设计,采用亲和取代的途径制备了含有甲氧基侧链的聚芳醚聚合物,然后去醚化得到了侧链含有羟基的聚芳醚材料,最后通过接枝的方法将磺酸基团引入聚合物成功的制备出多磺化侧链型聚芳醚质子交换膜材料。此类材料表现出好的热化学稳定性, 80 oC时的质子传导率可达到0.192 S/cm,超过了Nafion 117 薄膜的传导率.同时此类材料表现出低的尺寸稳定性。因此此类材料很有希望在质子交换膜领域得到应用     

Synthesis of fluorine‐containing star‐shaped poly(vinyl ether)s via arm‐linking reactions in living cationic polymerization

Various types of fluorine‐containing star‐shaped poly(vinyl ether)s were successfully synthesized by crosslinking reactions of living polymers based on living cationic polymerization. Star polymers with fluorinated arm chains were prepared by the reaction between a divinyl ether and living poly(vinyl ether)s with fluorine groups (C₄F₉, C₆F₁₃, and C₈F₁₇) at the side chain using cationogen/Et_1.5AlCl_1.5 in a fluorinated solvent (dichloropentafluoropropanes), giving star‐shaped fluorinated polymers in high yields with a relatively narrow molecular weight distribution. The concentration of living polymers for the crosslinking reaction and the molar feed ratio of a bifunctional vinyl ether to living polymers affected the yield and molecular weight of the star polymers. Star polymers with block arms were prepared by a linking reaction of living block copolymers of a fluorinated segment and a nonfluorinated segment. Heteroarm star‐shaped polymers containing two‐ or three‐arm species were synthesized using a mixture of different living polymer species for the reaction with a bifunctional vinyl ether. The obtained polymers underwent temperature‐induced solubility transitions in various organic solvents, and their concentrated solutions underwent sol–gel transitions, based on the solubility transition of a thermoresponsive fluorinated segment. Furthermore, a slight amount of fluorine groups were shown to be effective for physical gelation when those were located at the arm ends of a star polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

一种新型磺化聚醚醚酮的合成、表征和性能

以特丁基对苯二酚、3,3′-二磺酸钠基-4,4′-二氟二苯酮和4,4′-二氟二苯酮为单体,制备了具有高磺化度的聚醚醚酮.该系列聚合物可溶,并具有良好的成膜性.对聚合物及其膜的一些性能进行了研究.     

Effect of Halogen Chain End Fidelity on the Synthesis of Poly(methyl methacrylate-b-styrene) by ATRP

Poly(methyl methacrylate-b-styrene) (PMMA-b-PS) block copolymers are synthesized by two consecutive ATRPs and fractionated into four fractions. The halogen chain end fidelity (CEF) in PMMA-b-PS is quantified based on the analysis of each fraction.Compared to ethyl 2-phenyl-2-bromoacetate/CuBr/2,2′-bipyridine (EPBA/CuBr/bpy) and CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (CuBr/PMDETA) catalysts, PMMA-b-PS synthesized using p-toluenesulfonyl chloride/CuCl/bpy (TsCl/CuCl/bpy) and CuCl/PMDETA catalysts has a higher halogen CEF and a better control on molecular weight.     

Synthesis and properties of poly(ether imide)s based on the bis(ether anhydride)s from hydroquinone and its derivatives

Four bis(ether anhydride)s, 4,4′‐(1,4‐phenylenedioxy)diphthalic anhydride (IV), 4,4′‐(2,5‐tolylenedioxy)‐diphthalic anhydride (Me‐IV), 4,4′‐(2‐chloro‐1,4‐phenylenedioxy)diphthalic anhydride (Cl‐IV), and 4,4′‐(2,5‐biphenylenedioxy)diphthalic anhydride (Ph‐IV), were prepared in three steps starting from the nucleophilic nitrodisplacement reaction of 4‐nitrophthalonitrile with the potassium phenoxides of hydroquinone and various substituted hydroquinones such as methylhydroquinone, chlorohydroquinone, and phenylhydroquinone in N,N‐dimethylformamide, followed by alkaline hydrolysis and dehydration. Four series of poly(ether imide)s were prepared from bis(ether anhydride)s with various aromatic diamines by a classical two‐step procedure. The inherent viscosities of the intermediate poly(amic acid)s were in the range of 0.40–2.63 dL/g. Except for those derived from p‐phenylenediamine and benzidine, almost all the poly(amic acid)s could be solution‐cast and thermally converted into transparent, flexible, and tough polyimide films. Introduction of the chloro or phenyl substituent leads to a decreased crystallinity and an increased solubility of the polymers. The glass transition temperatures (T_g) of these polyimides were recorded in the range of 204–263°C. In general, the methyl‐ and chloro‐substituted polyimides exhibited relatively higher T_gs, whereas the phenyl‐substituted ones exhibited slightly lower T_gs compared to the corresponding nonsubstituted ones. Thermogravimetric analysis (TG) showed that 10% weight loss temperatures of all the polymers were above 500°C either in nitrogen or in air. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 665–675, 1999     

Synthesis of the block sulfonated poly(ether ether ketone)s (S-PEEKs) materials for proton exchange membrane

To improve the proton conductivity of sulfonated poly(ether ether ketone)s (SPEEK) with low sulfonated degrees, a series of block SPEEK copolymers were prepared by a two-stage one pot process: first the hydrophobic block was prepared with the desired length, then the monomers for the hydrophilic block were added to the first reactive flask to form block copolymers. Membranes were cast from their DMF solutions, and characterized by determining the ion-exchange capacity, water uptake, proton conductivity and mechanical properties. Block-3 with the longer hydrophobic chain shows enhanced performance than the random one in usage for PEM. SAXS was employed to investigate the microstructure effects on the above properties. Larger ionic cluster size and larger proton transport channel in block-3 SPEEK membranes are detected from the result of SAXS. It is believed that this microstructure feature attributes to the enhanced proton conductivity values of block-3 membrane at low IEC.     

Noncovalent Macromolecular Architectures of Oligo(p-phenylenevinylene)s (OPVs): Role of End Functional Groups on the Gelation of Organic Solvents

Summary: Self-assembly of a few OPV derivatives having different end functional groups to aggregates, fibrous networks and organogels are discussed. OPV1 and OPV2 functionalized with ester moieties form gels in nonpolar hydrocarbon solvents whereas OPV3 with carboxylic acid groups form gel from THF and dichloromethane. OPV4 with dicyano moieties form aggregates but could not gelate solvents. AFM and TEM studies revealed considerable difference in the morphology of the self-assembled structures of OPV1-4 . From the optical, morphological and gelation data it is concluded that the nature of the end functional groups strongly influences upon the self-assembly and gelation properties of OPVs.     

Synthesis of poly(silyl ether)s containing pendant chloromethyl groups by the polyaddition of bis(oxetane)s with dichlorosilanes

The polyaddition of bis(3‐ethyl‐3‐oxetanylmethyl) terephthalate (BEOT) with dichlorodiphenylsilane (CPS) using tetrabutylammonium bromide (TBAB) as a catalyst proceeded under mild reaction conditions to afford a polymer containing silicon atoms in the polymer main chain. A poly(silyl ether) (P‐1) with a high molecular weight (M_n = 53,200) was obtained by the reaction of BEOT with CPS in the presence of 5 mol % of TBAB in toluene at 0 °C for 1 h and then at 50 °C for 24 h. The structure of the resulting polymer was confirmed by IR and ¹H NMR spectra. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with dichlorosilanes proceeds smoothly to give corresponding poly(silyl ether)s with TBAB as the catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2254–2259, 2000