Preparation of polyimides utilizing the Diels–Alder reaction,II: Bis[N-(butadienyl-2-methyl)] amino arylenes with bismaleimides

Four new bisdienes were prepared from 2-bromomethyl-1,3-butadiene and N,N-diethyl benzidine; bis[4-(N-ethyl) aminophenyl]-p-diisopropylbenzene, 1,4-diamino-2,3,5,6-tetramethylbenzene and α,α′ bis(4-amino-3,5-dimethyl phenyl)-p-diisopropyl benzene. Polyimides were synthesized by the Diels–Alder reaction of these bisdienes and bis(4-maleimidylphenyl)methane and bis(3-maleimidylphenyl) sulfone. The polymers were soluble in m -cresol, dimethyl sulfoxide and chlorinated hydrocarbon solvents. Moderate thermal stability was observed by thermogravimetric analysis in air and nitrogen.     

SELF-ASSEMBLED MICRO-DOMAINS ON THE UPPERMOST SURFACE OF FLUORINATED POLY（CARBONATE URETHANE）S WITH FLUORINATED SIDE CHAIN ATTACHED ON HARD SEGMENTS

The surface phase separated structure of polyurethanes is always desired due to the advantage of better biocompatibility, compared with the homogeneous one. The key issue is how to control and characterize the surface morphology. In this work, we report the uppermost surface morphology of fluorinated poly(carbonate urethane)s with fluorinated side chains attached to hard segments as studied by AFM, XPS and contact angle measurement. A self-assembled micro-domain with the fluorinated side chain standing up on the uppermost surface has been proposed for polyurethane with higher fluorinated content, based on the result obtained     

TRANSIMIDIZATION IN THERMOPLASTIC POLYIMIDES*

In order to improve the processibility in thermoplastic polyimides, a new method, termed the"reactive plasticizer" approach, has been proposed. This method uses a small amount (5～15 mol%) of a lessactivated, weak nucleophilic diamine co-monomer as a "reactive plasticizer" to obtain copolyimide resinswhich possess relatively low viscosity at low temperatures and can be readily processed through the autoclavecycle at low pressures. During a high temperature treatment, the reactive plasticizers join the reaction to formhigh molecular weight copolyimides, and the preferred material properties are thus achieved. The mosteffective reactive plasticizer is aromatic heterocyclic diamines, such as 2, 6-diaminopyridine diamine (DAP),and the transimidization involved with a reactive plasticizer has been proposed to play a major role for thesuccess of this approach. In order to understand the transimidization mechanism, three steps have been takenin this research: first, a copolyimide system of 50% of DAP and 50% 1, 4 -bis [4-aminophenoxy] benzenediamine (DODA) with 100% of 2, 2'-bis[4-(3, 4-dicarboxyphenoxy)phenyl] propane dianhydride (Ultem~(R)DA) is prepared. Second, several specifically designed polyimide mixture systems were used, and they consistof two homopolyimides: one is Ultem~(R) DA-DODA, and the other is Ultem~(R) DA-DAP. The third step is toinvestigate two mixture systems in which Ultem~(R) DA-DODA is mixed with DAP monomer solution andUltem~(R) DA-DAP is mixed with DODA monomer solution. For all systems, with increasing degree oftransimidization upon heat-treatment, the chain structures of the mixtures and their thermal and dynamicmechanical transition behaviors are investigated via one-dimensional and two-dimensional nuclear magneticresonance, differential scanning calorimetry, and dynamic mechanical analysis experiments. Experimentalresults indicate that in the mixture of two homopolyimides, transimidization takes place much moreefficiently in solution than in the melt. For the two mixtures with monomer solutions, the transimidizationcan only be found in the mixture of Ultem~(R) DAP/DODA system in p-chlorophenol, and this process does noteffectively occur in the Ultem~(R) DODA/DAP system in p-chlorophenol, indicating that free DODA canefficiently attack the imide linkage of Ultem~(R) DA-DAP. The final product resulting from the transimidizationin the mixtures is a random copolyimide with a major population of DAP as end groups for the copolymersystem.     

Synthesis of hydroxyl-containing polyimides derived from 4,6-diamino-resorcinol dihydrochloride and aromatic tetracarboxylic dianhydrides

High T_g polyimides containing pendant phenolic hydroxyl groups were synthesized in high molecular weight via one-step solution polymerization of the dihydrochloride salt of 4,6-diaminoresorcinol with various commercially available dianhydrides. Polymerization proceeds via initial dissociation of diaminoresorcinol dihydrochloride to hydrogen chloride gas and diaminoresorcinol, followed by rapid dissolution of diaminoresorcinol and polymerization with the dianhydride monomer to afford soluble, fully-cyclized polyimide. The resulting poly(hydroxy-imide)s, which contain two phenolic hydroxyl groups per repeat unit, were soluble in amide solvents and dilute aqueous bases, displayed reasonably high glass transition temperatures and a high degree of water uptake. © 1994 John Wiley & Sons, Inc.     

Fluoropolymer materials and architectures prepared by controlled radical polymerizations

This review initially summarizes the mechanisms, merits and limitations of the three controlled radical polymerizations: nitroxide mediated polymerization (NMP), atom transfer radical polymerization (ATRP) or metal catalyzed living radical polymerization, and reversible addition-fragmentation chain transfer (RAFT) polymerization. This is followed by two parts, one dealing with homo- and copolymerizations of fluorinated methacrylates and acrylates, and a second where fluorinated styrenes, alone or in combination with other monomers, are the main issues. In these parts, initiators (including multifunctional and macroinitiators), ligands and other reaction conditions as well as some kinetics and conversions are discussed. Numerous possibilities for preparation of a variety of different block copolymers where one or more blocks are fluorinated are devoted particular attention. The advantageous properties and functionalities that can be obtained from these novel fluorinated materials and architectures are especially emphasized. Thus, various amphiphilic, biocompatible or low energy materials, fluorinated nanoparticles and nanoporous films/membranes as well as materials for submicron and nanolevel electronics have been fabricated. In addition, the possible fluorination of various surfaces through surface initiation is highlighted. A final part deals with the use of fluorine containing initiators and macroinitiators, and the applications on the novel materials derived thereof.     

3-三氟-2-羟基/氨基-1-氟代丙基膦酸酯的合成

Reaction of diethyl 2,2-difluoro-3-（a-methylbenzyl）imino-4,4,4-trifluoropropanephosphonate （3） with triethylamine afforded a mixture of normal [1,3]-proton shift reaction product 5 and its HF-eliminated compound 6Z in 1 ： 1 ratio. Upon hydrolysis, this reaction mixture gave solely 1,3,3,3-tetrafluoro-2-dioxypropanephosphonate （9）. Reaction of 3 with DBU provided only 6, in which the ratio of E/Z forms was dependent on the reaction conditions. Aqueous hydrolysis of 6 led to 9. Catalytic hydrogenation and hydrogenolysis of 6 gave geometric isomers of 11 as expected. The reaction mechanism involved was discussed.     

A new method for the synthesis of fluorinated vinyl sulfides and ketene dithioacetals

A new method was developed for the synthesis of fluorine-containing functionally substituted vinyl sulfides and ketene dithioacetals from the corresponding derivatives of -trifluoromethyl-substituted CH-acids and thiols in the presence of BF₃·NEt₃.     

Preparation and applications of novel amphiphilic fluoroalkyl end‐capped oligomers‐clay nanocomposites

Nonionic‐type amphiphilic fluoroalkyl end‐capped acryloylmorpholine and N,N‐dimethylacrylamide homooligomers were found to be new convenient intercalating agents for the achievement of an enlarged basal spacing of the clay layers to afford fluorinated oligomers‐clay nanocomposites. These novel fluoroalkyl end‐capped oligomers‐clay nanocomposites were found to exhibit good dispersibility and stability in aqueous and organic media, and were applied to the surface modification of traditional organic polymeric materials such as poly(methyl methacrylate). Copyright © 2006 John Wiley & Sons, Ltd.     

Radical copolymerization behavior of a highly fluorinated cyclic olefin with vinyl ether

The copolymerization of a highly fluorinated cyclic monomer, octafluorocyclopentene (OFCPE, M₁), with ethyl vinyl ether (EVE, M₂) was investigated with a radical initiator in bulk. Despite the poor homopolymerizability of each monomer, the copolymerization proceeded successfully, and the molecular weights of the copolymers reached up to more than 10,000. Incorporation of the OFCPE units into the copolymer led to an increase in the glass‐transition point. The copolymer composition was determined from ¹H NMR spectra and elemental analysis data. The molar fraction of the OFCPE unit in the copolymer increased and approached but did not exceed 0.5. The monomer reactivity ratios were estimated by the Yamada–Itahashi–Otsu nonlinear least‐squares procedure as r_1,OFCPE = ?0.008 ± 0.010 and r_2,EVE = 0.192 ± 0.015. The reactivity ratios clearly suggest that the copolymerization proceeds alternatively in the case of an excessive feed of OFCPE. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1151–1156, 2002     

Relative Rates for Plasma Homo- and Copolymerizations of a Homologous Series of Fluorinated Ethylenes

The relative rates of plasma homo- and Copolymerizations of ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene and tetrafluoroethylene (VF _x , x = 0–4, respectively) were determined in an rf, capacitively coupled, tubular reactor with external electrodes using identical plasma parameters. The deposition rates for VF _x (x = 1–3) and 20 different monomer blends, when plotted versus the F/C ratios of the monomers or monomer blends, followed a concave-downward curve situated above the straight-line joining the rates for VF₀ and VF₄. The deposition rates for VF _m /VF _n blends (m = 3 or 4; n = 0–2) likewise yielded concave-downward curves situated above the straight lines joining the rates for the respective monomers; the rates for VF _m /VF _n blends (m = 0 or 1; n = 1 or 2) yielded concave-upward curves situated below the straight lines joining the rates for the respective monomers; while the rates for VF₃/VF₄ blends fell along the straight line joining the rates for VF₃ and VF₄. The mechanisms for plasma (co) polymerizations of VF _x monomers responsible for the wide range of relative deposition rates remain to be elucidated.