Synthese und Charakterisierung von Poly(dimethylsilylen-co-phenylmethylidenen)

Synthesis and Characterization of Poly(dimethylsilylene-co-phenylmethylidenes) The synthesis of a series different poly(dimethylsilylene-co-phenylmethylidenes) D-PMBz was afforded by the reaction of α,α-dichlorotoluene and dimethyldichlorosilane with sodium as reductive agent at molar ratios Me₂SiCl₂:Cl₂CHPh = 9; 4; 2,3; 1,5; 1; 0,7; (D-PMBz 1-6 ) respectively. The reduced reactivity of the carbosilane bridge builder α,α-dichlorotoluene and dimethyldichlorosilane led to a variety of side reactions like parasilylation of phenyl groups and the insertion of the solvent xylene. The synthesized D-PMBz, obtained in solid unsoluble and viscous soluble fractions, were investigated by IR-, ¹H-, ¹³C- and ²⁹Si-NMR-spectroscopy. Furthermore the average molecular weights were measured by gelpermeation chromatography. The thermolysis to 1130°C gave the ceramic residues of the soluble poly(dimethylsilylene-co-phenylmethylidenes).     

Electrospun nanofibers from ferrocene-containing multiblock copolymers prepared via RAFT polymerization with F127 modified precursor

Electrospun nanofibers from copolymers composed of ferrocene side chains and PEO₁₀₀-PPO₆₅-PEO₁₀₀ (F127) were fabricated in chloroform and N,N–dimethyl formamide solutions (V/V = 95:5) at room temperature. Ferrocene-containing multiblock copolymers (PFcMA_n-F127-PFcMA_n) were synthesized through reversible addition-fragmentation chain transfer polymerization using s-1-dodecyl-s''- (α, α'-dimethyl-α''-acetic acid) trithiocarbonate (DDMAT) modified F127 with 2- (methacryloyloxy) ethyl ferrocencarboxylate (FcMA). The structures of as-obtained chemicals were characterized by FTIR, ¹H NMR, and ¹³C NMR. Additionally, the block copolymers molecular weight and polydispersity were measured using gel permeation chromatography. The electrochemical responsiveness of the polymers was investigated using cyclic voltammetry as well as the thermal stabilities of polymers and precursors were tested through DSC and TGA. The morphologies of electrospun fibers were observed through field emission scanning electronic spectroscopy and a fibrous diameter of 300–1100 nm was obtained. The results indicated that the suitable molecular weight of ferrocene -containing polymer would be processed in nanofibrous.     

Synthesis and characterization of novel aromatic-aliphatic poly(amide-imide-imide)s (PAII)

Novel poly(amide-imide-imide)s (PAII) were prepared by polycondensation of a new monomer synthesized from trimellitic anhydride and glutamic acid, followed by reflux condensing with thionyl chloride and several diamines. Polymers and monomers were characterized by ¹H NMR and FT-IR spectroscopy, elemental analysis and mass spectrometry. Inherent viscosities of the resulting polymers were in the range of 17–26 mL g^–1 (M_w 13 400–29 160, polydispersity (M_w/M_n) ca. 1.3–1.7), representing rather low molecular weights. The glass transition temperatures of the polymers were in the range of 210–285°C depending on the structure of diamines, and the thermal stability of the polymers was up to 400°C, comparable with that of polyimides and poly(amide imide)s. All the polymers synthesized are well soluble in aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and dimethylacetamide. Particularly, polymers containing oxydianiline and 4,4′-diaminodiphenyl sulfone were quite soluble in m-cresol, pyridine, nitrobenzene and tetrahydrofuran.     

Reaction kinetics in reactive extraction for chiral separation of α-cyclohexyl-mandelic acid enantiomers with hydroxypropyl-β-cyclodextrin

This paper reports on determination of the intrinsic reaction kinetics in reactive extraction of α-cyclohexyl-mandelic acid (α-CHMA) enantiomers with hydroxypropyl-β-cyclodextrin (HP-β-CD) in a modified Lewis cell, in which HP-β-CD dissolved in 0.1 mol/l NaH₂PO₄/H₃PO₄ buffer solution was selected as chiral extractant. α-CHMA enantiomers were extracted from an organic phase to an aqueous phase in the extraction module. The theory of extraction accompanied by chemical reactions has been used to obtain the intrinsic kinetics of this extraction module. The different factors affecting the extraction rate, such as agitation speed, interfacial area, initial enantiomers concentration in an organic phase as well as HP-β-CD concentration in an aqueous phase were separately studied. The experimental results demonstrate that the extraction reaction kinetics is fast. The reactions between α-CHMA enantiomers and HP-β-CD in a stirred cell fall in regime 3 and are first order with respect to α-CHMA enantiomers and second order with respect to HP-β-CD with forward rate constants of 6.9×10⁻² m⁶/(mol² s) and 2.5×10⁻² m⁶/(mol² s) for S-α-CHMA and R-α-CHMA, respectively. These data will be useful in the design of the extraction process.     

Synthesis and characterization of polyamides X 18

Step heating melt polycondensation was adopted in the preparation of polyamides based on 1,16‐octadecane diacid and α,ω? (CH₂)_2n diamines (n = 1–6). The structure was confirmed by various spectroscopic techniques (IR, Raman, ¹H‐NMR, and ¹³C‐NMR). High molecular masses were obtained only in the presence of an excess of diamine and when the diamine possessed low volatility. The molecular masses were between (0.94 and 2.1) × 10⁴ Da for all polyamides under consideration. An excellent correlation between size exclusion chromatography and ¹H‐NMR data was demonstrated in the measurement of the degree of polymerization. The melting temperatures of the polyamides decreased from polyamide 12 18 to polyamide 2 18 as the amide density along the molecular chain declined. No significant variation was observed in the glass‐transition and decomposition temperatures of the polyamides that were obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1565–1571, 2005     

Synthesis and Characterization of processable heat resistant poly (amide-imides) for high temperature applications

Summary A series of new polyamide-imides with high thermal stability were synthesized by direct polycondensation of imide containing diamines with various aromatic diacids using polar aprotic solvents. In this technique triphenylphosphite (TPP) and pyridine were used as condensing agents to form polyamide-imide through N-phosphonium salts of pyridine. The various imide containing diamines were prepared by reacting dianhydride (PMDA, BPTDA) with aromatic diamines such as phenylene diamine, 3,3’-dichloro 4,4’-diaminodiphenylmethane and 2,6-diaminopyridine in 1:2 ratio. The diacids containing flexible ether units were prepared by treating diol with aromatic acid (2,4-dichlorobenzoic acid). The polyamide-imides obtained by this technique were characterized by elemental analysis, FTIR and ¹H-NMR. The solubility of these polyamide-imides was found to be good in polar aprotic solvents such as NMP, DMF, and DMAc etc. The viscosity of the polyamide-imides were determined and found to be in the range of 1.21 to 1.76 dl/g indicating the formation of high molecular weight polymers. The thermal stability of the polymers was tested using DSC and the Tg values are in the range of 207–234 °C showing the high thermal stability of the prepared polymers.     

TiO2‐Oligoaldaramide nanocomposites as efficient core‐shell systems for wood preservation

Homogeneous core‐shell systems were obtained with a growth, in controlled steps, of several oligoamides on TiO₂ nanoparticles. Derivatives of natural compounds, such as l ‐tartaric acid and α,α′‐trehalose, were used as diesters in the polycondensation reactions with ethylenediamine. TiO₂ anatase was chosen because of its high photo‐activity and its antimicrobial activity. The TiO₂ nanoparticles had been previously activated then functionalized using two different coupling agents, and finally, the TiO₂‐oligoamide nanocomposites were synthesized using two synthetic pathways. The final products were characterized by ¹H NMR, ¹³C NMR, FT‐IR, and transmission electron microscope. These nanocomposites can show improved properties in comparison with the single components (TiO₂ nanoparticles or oligoamides), which are useful in many fields, such as antimicrobial coatings for surfaces in cultural heritage conservation. A nanocomposite (TiO₂‐polyethylenetartaramide) was used for applicative studies, and it has shown a good efficacy against fungal attack by Trametes versicolor on wood specimens (Fagus sylvatica). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42047.     

Preparation and stress-strain properties of aba block copolymers of α-methylstyrene and butadiene

ABA-type “tapered” block copolymers of α-methylstyrene (monomer A) and butadiene were prepared using four commercially available dilithio initiators. Polymerizations were run at 25°C in benzene solvent, or at 40°C with butadiene dissolved in neat α-methylstyrene. Although α-methylstyrene has a rather low ceiling temperature, triblock copolymers could be made at these temperatures by using α-methylstyrene concentrations well in excess of the [M]_e values at the respective temperatures. Its concentration was such that molecular weights of at least 15,000–20,000 for the A blocks could be attained. The course of the copolymerization at 40°C was followed, showing that copolymers containing about 40% α-methylstyrene could be formed in 4–8 hr, depending on the initiator used. They showed the usual behavior of triblock thermoplastic elastomers, with tensile strengths > 3000 lb/in.² at 24°C. However, because of the high T_g of poly(α-methylstyrene) (172°C), they also had tensiles of several hundred lb/in.² at 100°C, unlike comparable polymers with polystyrene end blocks, which have practically no strength at this temperature. Microstructures of polybutadienes made with these initiators are also given.     

Chemochromic properties of neutral polyaniline throughout cholesterol exposure

α-Bromo-ε-caprolactone (α-BrCL) was synthesized from α-bromocyclohexanone by using 3-chloroperoxybenzoic acid. α-BrCL was then used as a comonomer in the ring-opening polymerization of ε-caprolactone (CL) initiated with aluminum isopropoxide to synthesize poly(CL-co-α-BrCL) copolymer. This copolymer was used as the macroinitiator in the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) for the synthesis of stimuli-responsive and biodegradable PCL-g-PNIPAAm copolymer. A core-shell type nano-structure was formed with a hydrophilic outer shell and a hydrophobic inner core from these copolymers, which exhibited a phase transition temperature around 31 °C. The copolymers were characterized by ¹H-NMR and FT-IR spectroscopies. Number-average molecular weight of the poly(CL-co-α-BrCL) and PCL-g-PNIPAAm copolymers was calculated from corresponding ¹H-NMR spectra to be 5770 and 6810 gmol^?1, respectively. Thermal stability of the copolymer was investigated by thermogravimetric analysis (TGA) and crystallization behavior was studied by differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) showed that the self-assemble micelle aggregates had well defined spherical shape. From the fluorescence spectra, fluorescence intensity of pyrene in the copolymer micelles increased and red-shifted as the copolymer concentration increases, indicating the formation of self-assemble polymeric micelles in water. The critical micelle concentration was found to be 3.2?×?10^?3?mg/mL. TEM results showed that micelles have spherical shapes with a diameter of about 70 nm. The obtained micelles can be desirable for potential applications in biomedical fields, such as drug delivery systems.     

Polymers containing formamidine groups

Summary Aliphatic polyformamidines have been synthesized by reaction of aliphatic diamines with triethyl orthoformate in presence of catalytic amounts of acetic acid. The reaction has been carried out in DMSO at 180°C. The polymer structure has been confirmed by IR and NMR spectroscopy. For determination of molecular weights ¹H NMR end group signals have been used.     

Synthesis, characterization and electrostatic dissipating ability of poly(oxyethylene) block polyesteramides

Poly(oxyethylene)diamines were included in the copolymerization of ethylene glycol and dicarboxylic acids, such as terephthalic, adipic and sebacic acid, to produce a series of hydrophilic polyether-ester-amides. With the addition of poly(oxyethylene)diamines (average molecular weight of 2,000) to PET in the amounts of 3.2, 6.6, 12 and 16 wt%, melting points of these polymers dropped accordingly, from 240 °C to around 227 °C, and the electronic resistivity decreased from 1×10¹³ to approximately 8×10⁸ ohm/sq. For comparison, the introduction of hydrophilic PEG-2000 or a low molecular weight diamine, such as triethyleneglycol diamine, has less effect on electronic resistivity. Molecular weight, polymer rigidity and ageing are other factors affecting the surface resistivity. The degree of hydrophilicity was measured by the moisture absorption of the fibers made from these polyether-ester-amides. A weight gain of 0.96% was observed for 12 wt% poly(oxyethylene)diamine modified polyether-ester-amides in comparison with 0.40% for the unmodified polyethylene terephthalate). These results are explained by a mechanism involving moisture absorption on the polymer surface through the formation of hydrogen bonding with amide and-(OCH₂CH₂)-functionalities on the polymer surface.     

Synthesis of Gemini‐Like Methyl Acrylate‐Acrylic Acid‐Methyl Acrylate Triblock Copolymers Surfactants by RAFT Polymerization in Solution and Investigation of their Behavior at the Air–Water Interface

A series of methyl acrylate‐acrylic acid amphiphilic triblock copolymers (PMA‐PAA‐PMA) were prepared by solution polymerization using S,S′‐bis (α,α‐dimethy1acetic acid) trithiocarbonate (BDAT) as a reversible addition fragmentation chain transfer (RAFT) agent and methyl acrylate (MA) as the first monomer. The triblock copolymers and their common MA homopolymer precursors were characterized in terms of their compositions, molecular weights and behavior at the air–water interface using ¹H‐NMR spectroscopy, thermogravimetric analysis, gel permeation chromatography, surface tension, transmission electron microscopy (TEM) and dynamic light scattering respectively. The results indicated that PMA‐PAA‐PMA was successfully synthesized through RAFT polymerization. The polydispersity index (PDI) decreased when the molar ratio [n(MA)/n(AA)] increased, the lowest PDI was obtained at 5.23 wt% RAFT and the molecular weights were consistent with the theoretical value as the RAFT agent percentage varied. The polymer neutralized by sodium hydroxide solution shows a low critical micelle concentration (CMC), which was <10^?2 mol L^?1 in water. The A_min values increased and showed a maximum with decreased AA chain length. TEM showed that the neutralized polymer formed a special vesicle structure with large pore structure which led to a low CMC and surface tension of water.     

Synthesis of ring-shaped polyisoprene

Cyclization of α,ω;-dilithiopolyisoprenes has been achieved in hexane solution in the presence of tetrahydrofuran (15% in volume) at ?40 to - 50°C. Using as linking agent the non-conjugated diene 1,2-bis(isopropenyl-4-phenyl)-ethane, macrocyclic polyisoprenes could be obtained with yields of at least 90%, even for molecular weights as high as 30 000 mol g^?1. With SiCl₄ as coupling agent no gelation occurred and yields of about 70% in cyclic dimers, probably bicyclic, have been observed. These results are compared to those obtained by various authors with α,ω;-dilithiopolystyrenes or α,ω;-disodiopolystyrenes and are attributed mainly to the presence, in the polyisoprene case, of predominant cyclic aggregates even at low organolithium concentration.     

Physical nature of complex structural relaxation in polysiloxane - PMpTS: α and α′ relaxations

Structural relaxation processes in poly(methyl-para-tolyl-siloxane) (PMpTS) polymers of three molecular weights were studied using dynamic light scattering. Two relaxation processes: the usual α and an additional slow one α′ were observed and studied as function of temperature and molecular weight. Contrary to the structural relaxation, we find that in a plot T-T_g the relaxation times for the α′ process for all molecular weights do not collapse to a single curve. For one of the samples the light scattering correlation functions were compared with the corresponding functions obtained by means of mechanical relaxation, dielectric spectroscopy and computer simulations. The simulations show that the bimodal distribution, i.e. the α relaxation and the slow (α′) process are contained in the correlation functions of most of the probes (optical anisotropy, dipole moment, chain bond, density) in agreement with experimental observations.     

Study on morphology,thermal, mechanical and Cd(II) adsorption properties of PVC/α-MnO<Subscript>2</Subscript>-stearic acid nanocomposites: production and application

Alpha manganese dioxide nanorods (α-MnO₂) were successfully functionalized with stearic acid (SA) by solvothermal method to prevent agglomeration. The α-MnO₂-SA nanorods were employed as a filler for the preparation of poly(vinyl chloride) (PVC) nanocomposite (NC) films with different percentages (1, 3 and 5 wt%). The morphology, mechanical and thermal properties of the obtained NCs were investigated. The results showed that α-MnO₂-SA can effectively improve the properties of PVC. The enhancement in properties of the NCs was attributed to the improved interfacial bonding by modification. Also, these NCs were used as adsorbent for removal of cadmium ions. Our finding suggests that the PVC/α-MnO₂-SA NCs are good candidates for efficient Cd(??) removal from the wastewater.     

Broadband dielectric spectroscopy of nanostructured maleated polypropylene/polycarbonate blends prepared by in situ polymerization and compatibilization

The miscibility and molecular dynamics of nanostructured maleated polypropylene (mPP)/polycarbonate (PC) blends prepared by in situ polymerization of macrocyclic carbonates with polypropylene modified with 0.5 wt% of maleic anhydride-reactive groups were investigated over a wide range of frequencies (10⁻²-0.5 × 10⁷ Hz) at different constant temperatures using broadband dielectric spectroscopy and scanning transmission electron microscope (STEM). The molecular dynamics of the glass relaxation process of the blend (α-relaxation process) appeared at a lower temperature range compared with that of the pure PC. This shift in the molecular relaxation process is attributed to the partial miscibility of the two polymer components in the blends as previously confirmed by the morphology via STEM. Nanoscale morphologies with average domain diameters as small as 50 nm were obtained for the different blend compositions studied. The STEM photographs show that the graft mPP-g-PC prefers to locate at the interfaces as previously reported. The relaxation spectrum of pure PC and mPP/PC blends was resolved into α- and β-relaxation processes using the Havriliak-Negami equation and ionic conductivity. The dielectric relaxation parameters, such as relaxation peak broadness, maximum frequency, f_max, and dielectric strength, Δ? (for the α- and β-relaxation processes), were found to be blend composition dependent. The kinetics of the α-relaxation processes of the blends were well described by Vogel-Fulcher-Tammann (VFT) equation. The local process of PC was resolved into two relaxation processes β₁ and β₂, associated with the carbonyl groups' motion and the combined motions of carbonyl and phenylene groups, respectively. Only β₂ shifted to lower frequency in the blend while β₁ was relatively not affected by blending. The electric modulus of the blends was used to get a sufficient resolution of the different relaxation processes in the samples, i.e., α-, β-relaxation processes, ionic conductivity, and interfacial polarization. In addition, the blending method used was found to increase the d.c. conductivity without affecting the charge carrier transport mechanism, making it possible to develop novel polymer blends with tunable dielectric properties and morphology from existing polymers.     

Synthesis and characterization of soluble poly(amide‐imide)s bearing triethylamine sulfonate groups as gas dehumidification membrane material

A series of soluble poly(amide‐imide)s (PAIs) bearing triethylammonium sulfonate groups were synthesized directly using trimellitic anhydride chloride (TMAC) polycondensation with sulfonated diamine such as 2,2′‐benzidinedisulfonic acid (BDSA), 4,4′‐diaminodiphenyl ether‐2,2′‐disulfonic acid (ODADS), and nonsulfonated diamine 4,4‐diaminodiphenyl methane in the presence of triethylamine. The resulting copolymers exhibited high molecular weights (high inherent viscosity), and a combination of desirable properties such as good solubility in dipolar aprotic solvents, film‐forming capability, and good mechanical properties. Wide‐angle X‐ray diffraction revealed that the polymers were amorphous. These copolymers showed high permeability coefficients of water vapor because of the presence of the hydrophilic triethylammonium sulfonate groups. The water vapor permeability coefficients (P_w) and permselectivity coefficients of water vapor to nitrogen and methane [α(H₂O/N₂) and α(H₂O/CH₄)] of the films increased with increasing the amount of the triethylammonium sulfonated groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of new polyesters with chelating subunits by solution and interfacial polycondensation

New polyesters have been prepared by solution and interfacial polycondensation of acid chlorides obtained from bis‐α,ω‐polymethylene‐[(2‐methoxy)phenoxy]acetic acids, acid‐ether siderophores AE _n (n being the number of methylene units), and diols including bisphenol A, ethylene glycol and propanediol. For interfacial polycondensation, average molecular weights range from 1000 to 4500 g mol^?1; at higher temperature the molecular weights increase but the yield is smaller. Differential scanning calorimetry shows T_g ranging from ?5 to + 110 °C. Polyesters are crystalline with n = 6 and amorphous with n = 2 and 4; in addition, increasing n in AE _n increases molecular weights and T_g values. In solution polycondensation, the average molecular weights are around 3000 g mol^?1 and T_g is low. © 2001 Society of Chemical Industry     

Polypentamethylnadimides obtained by Diels-Alder reaction

The reactions between benzylbromide or α,α′-dibromo-meta-xylene (DBMX) and sodium 1,2,3,4,5-pentamethylcycopenta-1,3-dienide (CpMe₅^?, Na^⊕) give only the expected pentamathylcyclopentadiene derivatives with a good yields. These products lead to endo isomer adducts via a Diels-Alder reaction with maleimide.New low molecular weight polypentamethylnadimides were obtained in this way from the Diels-Alder polymerization of bispentamethylcyclopentadiene monomers and commercial or synthetic bismaleimides. The polyadducts were characterised by size exclusion chromatography (SEC), matrix assisted laser desorption ionization-time of flight (MALDI-TOF), nuclear magnetic resonance (NMR) and thermogravimetric analyses (TGA).The low molecular weight was attributed to methyl steric hindrance. For the lowest molecular weight products, two different endcapped oligomers were observed.     

Some biophysical properties of castor oil esterified with some acid anhydrides

A series of castor oil adducts were synthesized by esterification of castor oil with acid anhydrides: phthalic, maleic and succinic anhydrides. The chemical structure of castor oil and the prepared adducts were characterized by means of IR and ¹H NMR spectroscopy. The number‐average and weight‐average molecular weights were measured by gel permeation chromatography. The electrical properties were studied through the permittivity, dielectric loss and conductivity measurements, which are considered to be in the range of electrical insulation. The electrical conductivity, which describes the ionic mobility of the systems, was found to be in the range of 10^–9 to 10^–12 S/cm. This indicates that castor oil and its esters could be used for antistatic applications. The viscosity η and the activation energy E_η, obtained from the dependency of viscosity on temperature using the Arrhenius equation, were found to increase with increasing molecular weight of the system. The effect of different concentrations of castor oil and its esters on the growth activities of the sugar beet pathogens R. solani and S. rolfsii was studied through the determination of percent germination, average length of hyphal extensions, dry mass yield and the production of sclerotia. The obtained data indicate that the esterification of castor oil with anhydrides improves the antifungal activity.