Chemical oxidative polymerization of m-phenylenediamine and its derivatives using aluminium triflate as a co-catalyst

Aromatic diamine monomers, including m-phenylenediamine (mPD), 2-methyl-m-phenylenediamine (2Me-mPD), 4-methyl-m-phenylenediamine (4Me-mPD) and trimethyl-m-phenylenediamine (tMe-mPD), were polymerized by chemical oxidation using ammonium persulfate as an oxidant. Aluminium triflate (Al(OTf)₃) was also used for the first time as a co-catalyst under various polymerization conditions. The polymerization yield was improved when Al(OTf)₃ was introduced to the polymerization reaction for most polymers. The poly(2-methyl-m-phenylenediamine) (P(2Me-mPD)), poly(4-methyl-m-phenylenediamine) (P(4Me-mPD)) and poly(trimethyl-m-phenylenediamine) (P(tMe-mPD)) polymers exhibited better solubility than poly(m-phenylenediamine) (P(mPD)) polymers in most common solvents. The homopolymers obtained were characterized by FT-IR, ¹H and ¹³C NMR, WAXD and TGA. The results showed that the yield, solubility and structure of the polymers are significantly dependent on the polymerization conditions. TGA measurements indicated that the polymers have good thermal stability and decompose above 400 °C in nitrogen.     

Template-assisted hydrogelation of a dynamic covalent polyviologen-based supramolecular architecture via donor-acceptor interactions

A novel polyviologen-based molecular architecture was developed via the step-growth polymerization of a hydroxyl-substituted aryl dihydrazide with a water soluble viologen-dialdehyde in water under acidic conditions. When polymerized in the presence of π-electron rich aromatic templates, the reaction mixture underwent hydrogelation. The templates were found to facilitate monomer-monomer as well as monomer-polymer preorganization during polymerization via donor-acceptor charge transfer interactions. Following polymerization, the templates effectively served as post-synthetic non-covalent cross linkers connecting the hydrogel network. The chemical structures of the polymers and molecular recognition between the reacting species were investigated in solution using ¹H NMR, while donor-acceptor charge transfer interactions were investigated using UV-vis absorption spectroscopy. We also report the hydrochromic behavior of the templated and non-templated polymers. The surface morphology of the polymers was characterized using scanning electron microscopy, which revealed the formation of sheet-like structures. The new hydrogels developed in this work represents an interesting example of materials comprised of reversible dynamic covalent bonds and reversible non-covalent crosslinking interactions occurring between the electron-rich aryl templates and the electron-deficient bipyridinium units.     

Synthesis of optical-active azo-containing acrylates using atom transfer radical polymerization under microwave irradiation

Microwave irradiation (MI) was applied to the atom transfer radical polymerization (ATRP) of azo-containing acrylates. The polymerization was greatly promoted and the reaction time was shortened from several days to about 1 h. The polymerization was well-controlled within an incipient period but it was influenced by “hyperthermia effect” after a certain time. The functional polymers obtained under MI process have good third-order nonlinear optical (NLO) properties as those of polymers obtained under CH process.     

New processable poly(ether-keto-sulfone)s,poly(arylene sulfone)s,and polyesters curable by intramolecular cyclization. XVII

New processable polyaromatic ether-keto-sulfones were prepared from 2,2′-diiododiphenyl-4,4′-dicarbonyl dichloride (I), bis(p-phenoxybenzene)sulfone (V), isophthaloyl chloride (VI), terephthaloyl chloride (VII), and diphenylether (IX) in Friedel-Crafts-type polymerizations. By varying (VI):(VII) ratio and (V):(IX) ratio and by reducing the polymerization time, soluble, processable polymers were obtained. In these polymers, phenylacetylenyl groups were introduced by replacing the iodine. This process led to soluble and curable polymers. Transparent, tough films and fairly flexible glass fiber laminates can readily be prepared. After curing, the polymers were insoluble and showed excellent chemical and thermal resistance. The curing process increased the polymers' softening temperature by ca. 20°C and produced intersting new useful materials for laminates. Processable poly(arylene sulfone)s were prepared from I, V, and diphenylether-4,4′-disulfonylchloride (X) in a Friedel-Crafts-type polymerization. Different monomer ratios and polymerization times were used. Only low-molecular-weight polymers were obtained. The same result was shown by curable polyester formation from I, VI, VII, and 4,4′-sulfonyldiphenol (XI) in an interfacial polycondensation.     

The calorimetric determination of the ceiling temperature for the chemical polymerization of pyrrole

The previously found strong dependence of the polymerization enthalpy on the reaction temperature has been rationalized. The temperature dependence is to be ascribed to the existence of a ‘ceiling temperature’ for the polymerization process of the pyrrole monomer. The determined ceiling temperature has beenT?350 K when FeCl₃ was used as the oxidizing agent in CH₃CN solution. The existence of a ceiling temperature together with its already determined exoenthalpic nature allows to classify the polymerization reaction as an exoentropic one. From the dependence of the yield of insoluble polymer on the reaction temperature, the trend of the relative mean numeral molecular massM _n for the different obtained polymers has been determined. Measurements of electrical conductivity on pressed pellets of the different polymers allowed to establish a correlation between theM _n value and the conductivities The dependence of the conductivity on the exposition time to the air allowed to do some essays on the aging behaviour of the obtained polypyrrole. By making some assumptions, an absolute calorimetric determination of the value ofM _n of polypyrrole was tempted together with that of the related poly-N-vinilpyrrole.     

Synthesis of biocidal polymers containing metal NPs using an electron beam

Metal containing antibacterial polymers were prepared by the polymerization of methylmethacrylate and methacrylic acid with copper or zinc. When the thin film of the polymers coated on a glass was irradiated with an electron beam, nanoparticles were obtained. It was found that these polymers exhibited a potent antibacterial activity against the Gram-negative bacteria, Escherichia coli. The metal containing polymers showed a 99.999% (5.0 logs) reduction in E. coli at a contact time of 12 h.In addition, polymers had a good antifouling effect against marine organisms.     

Stereospecific radical polymerization of optically active (S)-N-(2-hydroxy-1-phenylethyl) methacrylamide catalyzed by Lewis acids

The effects of Lewis acids, namely, rare earth metal trifluoromethanesulfonates, on the radical polymerization of (S)-N-(2-hydroxy-1-phenylethyl) methacrylamide were examined under various conditions. In the absence of Lewis acids, syndiotactic-rich polymers (r = 84%) were obtained, whereas in the presence of a catalytic amount of Lewis acids, the polymerization proceeded in an isotactic-specific manner (m up to 64%). Polymerization solvents strongly influenced the effect of the Lewis acids. The polymerization in n-butyl alcohol showed the highest isotactic selectivity, whereas the polymerization in DMSO showed no isotacticity-enhancing effect. Further increases in the Lewis acid concentration and the polymerization temperature did not produce clear effects on the tacticity of the polymers. The interaction between the monomer and Lewis acids was investigated, and the plausible mechanism of stereocontrol in the radical polymerization of (S)-HPEMA was analyzed based on the Lewis acid-monomer interaction.     

Rhodium-catalyzed hydrothiolation of alkynes with thiols for construction of sulfur-containing π-conjugated systems

To synthesize sulfur-containing π-conjugated polymers, reaction conditions for rhodium-catalyzed hydrothiolation of terminal alkynes with arenethiols are optimized in detail. Under the optimized conditions, rhodium-catalyzed hydrothiolation of terminal alkynes proceeds regio- and stereoselectively to afford the corresponding vinyl sulfides via an anti-Markovnikov and syn-addition process. Then, the rhodium-catalyzed hydrothiolation is applied to polymerization of 2,5-diethynylthiophene with benzene-1,4-dithiol, which successfully provides sulfur-containing π-conjugated polymers with excellent regio- and stereoselectivities.     

Comparative studies of chemically synthesized polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid

Polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid (p-TSA) were synthesized by in situ chemical polymerization method using ammonium per sulphate as an oxidizing agent. This is a novel polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV-Vis and FT-IR spectroscopy, SEM, elemental analyzer, TGA/DSC and conductivity measurements. Thermal analysis shows that poly(o-toluidine) is less thermally stable compared to polyaniline. The less conductivity in poly(o-toluidine) is due to the cumulative steric as well as electronic effect of the bulky methyl substituent present on the benzene ring. High temperature conductivity measurements show ‘thermal activated behavior’.     

丙烯腈在1-丁基-3-甲基咪唑氯化物中的聚合及其表征

以离子液体1-丁基-3-甲基咪唑氯化物([bmim]Cl)为溶剂,研究了丙烯腈(AN)的自由基均聚和共聚反应,通过红外光谱(FT-IR)和核磁共振(NMR)分析了聚合产物的化学结构,研究了第二单体丙烯酸甲酯(MA)的含量对聚合反应速率及转化率的影响.结果表明:以离子液体为溶剂所得聚丙烯腈(PAN)的化学结构与在常规溶剂中的一致,聚合产物的组成比与投料比接近,分子量随着AN含量的增加而增大,反应转化率随着AN含量的增加先增大后减小,所得PAN的分子量分布窄(<1.7)、分子量高.差示扫描量热分析(DSC)结果表明:MA含量低于2%时有利于环化反应的控制.     

New functionalized polyesters to achieve controlled architectures

Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1-di-n-butyl-stanna-2,7-dioxacyclo-4-heptene as the initiator in the ring-opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of ϵ-caprolactone resulted in poly(ϵ-caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L -lactide polymers, and the two reactions were compared in this study. The conversion of ϵ-caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L -lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with ϵ-caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated CC double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L -lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m-chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 444–452, 2004     

Polymerlzatlon of 1-Ethynyl-1-Cyclohexanol by Radiation,Electroinitiation, and Chemical Catalysts

Abstract

Solid-state polymerization of 1-ethynyl-1-cyclohexanol was carried out by irradiation in vacuum and in open air at 20°C. Radiation-induced polymerization was also done in a benzene solution. The products were mixtures of oligomers and polymers. IR, NMR, U V, and x-ray investigations showed the initial formation of trimer, oligomer, and polymer. The polymer fraction increased with an increase of conversion. Electro-initiated polymerization gave soluble and insoluble fractions. The soluble fraction was an ether. However, the results were not reproducible. No polymers were obtained with n-butyllithium and borontrifluoride etherate as chemical catalysts.     

双-(β-酮萘胺)镍(II)/B(C6F5)3/AlEt3体系催化醋酸降冰片烯酯聚合及结构表征

采用双-(β-酮萘胺)镍(II)/B(C6F5)3/AlEt3体系在甲苯溶剂中进行了降冰片烯衍生物醋酸降冰片烯酯的聚合,研究了聚合温度和聚合时间对聚合的影响。通过1H NMR、13C NMR、FT-IR、DSC及WAXD技术对聚合物的结构和性能进行了研究。证明双-(β-酮萘胺)镍(II)/B(C6F5)3/AlEt3体系催化醋酸降冰片烯酯按乙烯基加成聚合方式进行的,聚合物分子量中等和分子量分布较窄。所得聚合产物为非晶态,具有短程有序长程无序的特征,热稳定性较好,并能够溶解在大部分普通有机溶剂中。     

N,N′-Diaminoethane linked bis-TEMPO-mediated free radical polymerization of styrene

The N,N′-diaminoethane linked bis-TEMPO nitroxide (C2)-mediated free radical polymerization of styrene at 135 °C in bulk was studied. It was found that under comparable conditions a single nitroxide group of C2 biradical retards the polymerization more than TEMPO. The results were discussed in terms of through-space interactions between two TEMPO moieties of C2 biradical and diffusion effects. According to experimental results analyzed by means of statistical methods, the polymerization system displays a bimodal molecular-weight distribution (MWD) from the beginning of the polymerization process, most probably by undergoing decomposition side reactions leading to irreversible polymer arm (P) separation from PC2P to PC2 and PC2H alkoxyamines. The scale of the decomposition depends rather on the time the system is maintained at the polymerization temperature than on conversion of monomer. Generally, the contribution of low molecular weight chains to overall MWD increases with time of polymerization whereas the contribution of high molecular weight chains to MWD increases for less controlled polymerization systems. For polymers obtained at high [dinitroxide]/[initiator] ratio, the thermal treatment of polystyrene in mass at 135 °C unexpectedly revealed an increase of M_n, which can probably be ascribed to post-polymerization effects involving polystyrene with unsaturated chains end groups.     

Sulfur containing polymers.: Aromatic polydithiocarbonates and polythiocarbonates: synthesis and thermal properties

New polydithiocarbonates and polythiocarbonates were obtained by interfacial polymerization of bis(4-mercaptophenyl)methane, bis(4-mercaptophenyl)ether and bis(4-mercaptophenyl)sulfide with phosgene, bisphenol A bischloroformate and bisphenol A polycarbonate oligomers (-OH/-O-CO-Cl terminated). Polymerization process was carried out under interfacial conditions using a phase-transfer catalyst, as earlier described for the synthesis of polydithiocarbonates and polythiocarbonates from 2,2-bis(4-mercaptophenyl)propane. The structures of the polymers were examined by IR and NMR spectroscopies; their thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. In particular, the effect of the substitution of one or both the ethereal oxygen atoms of the carbonate group by sulfur has been analyzed by comparing the T_g values and the ability to crystallize of the sulfur containing polymers with those of the corresponding polycarbonates.     

Preparation and characterization of polydimethylsiloxanes with narrow molecular weight distribution

The preparation of polydimethylsiloxanes (PDMS) of narrow molecular weight distribution (MWD) by anionic polymerization of hexamethylcyclotrisiloxane (D₃) in an improved polymerization apparatus is described. Using (CH₃)₂Si(OLi)₂ as initiator and (CH₃)₃SiCl (TMCS) as terminating agent, polymers with only methyl groups were obtained with molecular weights ranging from 2 × 10³ to 2 × 10⁶. Kinetic investigations were performed only so far as necessary for controlling the polymerization under the chosen experimental conditions (solvent: n-hexane, solvating agent: hexamethylphosphortriamide (HMPT), polymerization temperature: 25°). The molecular weights of the polymers were determined by light-scattering and, after calibration, by viscometry and GPC. The non-uniformities of the samples with symmetrical MWD were estimated using the 4σ-method. The GPC apparatus had been calibrated with polystyrene and poly-α-methylstyrene samples of extremely small non-uniformity.     

Synthesis of ultra-high-molecular-weight polyacrylonitrile by anionic polymerization

The anionic polymerization of acrylonitrile in DMF initiated by lithium 1,2-bis(diethylamino)-2-oxoethanolate in the range ?60 to 0°C has been studied. The initiator efficiency at low temperatures (?60 to ?40°C) is 2–6%; it remains nearly invariable with conversion owing to the associated state of the initiator. The low concentration of growing active centers is constant throughout the process; as a result, polymers with M > 3 × 10⁵ are produced. The polymers are characterized by a narrow molecular-mass distribution, M _w/M _n = 1.3–1.6, and contain insignificant amounts of low-molecular-mass fractions. It has been shown that controlled polymerization processes can be carried outat moderately low temperatures (?30 to 0°C), and experimental conditions for freezing of polymerization and its recommencement have been ascertained. Optimum conditions for the synthesis of a high-molecular-mass polyacrylonitrile with M > 3 × 10⁵ have been established, and the method for preparing polymers with M = (6.50–8.5) × 10⁵ on an enlarged scale using high concentrations of the monomer has been developed.     

Reversible Addition‐Fragmentation Chain‐Transfer Polymerization for the Synthesis of Poly(4‐acetoxystyrene) and Poly(4‐acetoxystyrene)‐block‐polystyrene by Bulk,Solution and Emulsion Techniques

The living radical polymerization of 4‐acetoxystyrene via the RAFT process has been achieved employing bulk, solution and emulsion techniques. The rate of polymerization was studied between 60°C and 90°C. Increasing the temperature increases the rate of polymerization without affecting the polydispersity. Poly(4‐acetoxystyrene) with narrow polydispersity (1.08) was obtained. Various novel dithiocarboxylic esters and dithiocarbamates were screened as chain‐transfer agents for the RAFT polymerization of 4‐acetoxystyrene. The block copolymerization of poly(4‐acetoxystyrene) with styrene leading to poly(4‐acetoxystyrene)‐block‐polystyrene confirmed the presence of active chain ends in the first block. The acetoxy polymers were hydrolyzed to the corresponding hydroxy polymers under mild basic conditions.     

Synthese de polymeres possedant des fonctions du type carbonate-alcool et thiol carbonate-alcool en extremites de chaines

Anionic polymerization permits the synthesis of polymers having various functional endgroups by deactivation of living polymers with the aid of electrophiles. These functional end-groups, as in the case of low molecular weight polymers, are easily accessible to reagents and can be subjected to chemical modification. Using this method, it is possible to obtain oligomers carrying functional end-groups of types which cannot be created by direct polymerization. This technique was applied to the synthesis of polydienes having carbonate alcohol and thiolcarbonate alcohol functional end-groups. These end functions were obtained by chemical modification of existing alcohol groups. In order to specify the experimental conditions, a model study of such a reaction was carried out. The polymers and their models are characterized by NMR, i.r. and physico-chemical measurements. This type of chemical modification leads to prepolymer having easily hydrolysed carbonate and thiolcarbonate linkages, reactive points for the subsequent degradation of the corresponding reticulated systems.