Glass transition temperature modification of acrylic and dienic type copolymers of 4-chloromethyl styrene with incorporation of (Me3Si)3C- groups

The new functional styrenic monomer, 4-trisylmethyl styrene (TsiMS) [Tsi=trisyl=tris(trimethylsilyl)methyl], was synthesized by reacting 4-chloromethyl styrene (CMS) with trisyllithium (TsiLi) in tetrahydrofuran (THF) solvent in the presence of copper chloride (CuCl). Attempt for the free radical polymerization of TsiMS by α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator at 70 ± 1 °C failed for several periods of times. This result showed that the trisyl group is a highly sterically hindered substituent and, subsequently, TsiMS becomes resistant for polymerization. Therefore, for preparation of new methacrylic, acrylic and dienic copolymers of TsiMS, we firstly synthesized the copolymers of CMS with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA) and isoprene (IP) by free radical polymerization method in toluene solution at 70 ± 1 °C using AIBN initiator to give the copolymers I-VI in good yields. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). The trisyl groups were then covalently attached to the obtained copolymers as side chains by reaction between excess of TsiLi and benzyl chloride bonds of CMS units, to give the copolymers - in 80-92% yields. All the resulted polymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility of all the copolymers was examined in various polar and non-polar solvents. The glass transition temperature (T_g) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. The T_g value of copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in polymer side chains, create new macromolecules with novel modified properties.     

Synthesis and characterization of polyesters derived from succinic acid, ethylene glycol and 1,3-propanediol

Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters with various compositions were synthesized through a direct polycondensation reaction with titanium tetraisopropoxide as the catalyst. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The compositions and the sequence distributions of the copolyesters were determined by analyses of ¹H NMR and ¹³C NMR spectra. The sequence distributions of ethylene succinate units and trimethylene succinate (TS) units were found to be random. Their thermal properties were characterized using differential scanning calorimeter and thermal gravimetric analyzer. All of the copolymers exhibit a single glass transition temperature (T_g). There is no significant difference in the thermal stability among these polyesters. Wide angle X-ray diffractograms (WAXD) were obtained for polyesters which can be crystallized isothermally. The results of thermal analysis and the WAXD patterns indicate that the incorporation of TS units into PES significantly inhibits the crystallization behavior of PES. Additionally, the crystal pattern of PTS is quite different from that of PES. Dynamic mechanical properties of moldable polyesters were investigated using a Rheometer operated at 1 Hz. Below T_g, the incorporation of TS units into PES results in the decline of storage modulus. Above T_g, the effect of crystallinity on the storage modulus can be found.     

Poly(methylmethacrylate-dimethylsiloxane) triblock copolymers synthesized by transition metal mediated living radical polymerization: bulk and surface characterization

Well-defined poly(MMA-b-DMS-b-MMA) triblock copolymers were prepared by copper(I) mediated living radical polymerization. This was achieved by polymerization of methylmethacrylate (MMA) with different concentrations of 2-bromoisobutyrate terminated polydimethylsiloxane (PDMS). The polymerization occurred in controlled manner with the molecular weight found by ¹H NMR close to that predicted and a narrow molecular weight distribution (M_w/M_n∼1.2). Copolymers were obtained with M_n=2100, 4900, 10 100 and 29 500 g mol⁻¹ respectively with poly(MMA) (PMMA) terminal blocks and a central PDMS block of 5500 g mol⁻¹ in each case.DSC analysis showed most of the poly(MMA-b-DMS-b-MMA) triblock copolymers exhibits two T_g’s, one at low temperature corresponding to the T_g of PDMS microphase and a second at high temperature corresponding to the T_g of the PMMA microphase. TEM images show microphase segregation morphology in bulk for the triblock copolymers, with a higher degree of segregation for copolymers containing higher PDMS content. XPS measurements were performed to determine the chemical composition at the surface. For all the copolymers PDMS enrichment is observed at the surface. Copolymers containing higher percentage of PDMS exhibit higher phase separation and better enrichment of PDMS at the surface. The surface tension determined by contact angle measurements of the copolymer film containing 59 mol% of PDMS was 19.15 mN m⁻¹.     

New fluorinated polymers bearing pendant phosphonic groups for fuel cell membranes: Part 1 synthesis and characterizations of the fluorinated polymeric backbone

Radical copolymerizations of chlorotrifluoroethylene (CTFE) with vinyl ethers such as 2-chloroethyl vinyl ether (CEVE) and ethyl vinyl ether (EVE) were performed at 75 °C in the presence of peroxide initiator. Three copolymers were obtained and characterized by means of both NMR and elemental analysis. Then, the chlorine atoms in the side chains were converted into iodine atoms by nucleophilic substitution, which was monitored by ¹H NMR spectroscopy. A series of five copolymers with different amounts of iodine atoms in the side chains were thus obtained. These copolymers exhibited molecular weight values of about 25,000 g mol⁻¹, and the thermal analysis of the copolymers showed a starting degradation from about 220 °C. The T_g values were in the range of 34-41 °C and showed a linear dependence versus the content of iodine atoms.     

Novel fluoroacrylated copolymers: synthesis, characterization and properties

The development of polymer waveguides leads to synthesis of fluorinated amorphous polymers with high transmission capacity, potential to tune their optical properties by tailoring the molecular structure, together with good processability, easy handling, good flexibility and low cost.In this work we have investigated new thermoplastic fluoroacrylated copolymers, synthesized by radical copolymerization of fluoroalkene(s) with five-membered cyclic carbonate and a third monomer or transfer agent, both containing OH group susceptible to be used for grafting of photocrosslinkable groups. The reaction of hydroxy functionalized copolymers with different acrylating agents results in fluoroacrylated resins with molecular weight in the range of 2000-3000 g mol⁻¹, yield >75% and good solubility in reactive diluents. In the presence of photoinitiator(s), they were crosslinked under UV-radiation in order to obtain optical waveguides.The copolymers synthesized were characterized by ¹H, ¹⁹F and ¹³C NMR as well as FT-IR spectroscopies and have good thermal stability (T_d > 200 °C). The refractive indeces of hydroxy functionalized fluorooligomers and acrylated resins were found to range from 1.44 to 1.45 at 23 °C and the T_gs (by DSC) varied from 40 to 110 °C depending on the content of the cyclic monomer. The optical characteristics of these thermoplastic fluoroacrylated copolymers are under progress.     

Synthesis characterizations and properties of a new fluoro-maleimide polymer

Novel 4-(4-trifluoromethyl)phenoxy N-phenyl-maleimide (FPMI) was synthesized. The free radical-initiated polymerization of FPMI was carried out in 1,4-dioxane solution using azobisisobutyronitrile as initiator. The monomer was investigated by FTIR, ¹H NMR, ¹³C NMR and elemental analysis, while the polymer was investigated by FTIR, ¹H NMR and ¹³C NMR. The effect of the monomer concentration, initiator concentration and temperature on the rate of polymerization (R_p) was studied. The activation energy of the polymerization was calculated (ΔE = 48.94 kJ/mol). The molecular weight of PFPMI and polydispersity index of the polymer were determined by gel permeation chromatography and were equal to 73,500, 16,700 and 2.27, respectively. The properties of PFPMI, including thermal behavior, thermal stability, the glass transition temperature (T_g = 236 °C), photo-stability, solubility and solution viscosity were studied.     

Thermal and rheological behaviours of some random aromatic amino-ended polyethersulfone/polyetherethersulfone copolymers

The thermal and rheological characterizations of seven random, low molecular weight (M_n ≅ 9500 g mol⁻¹), H₂N-ended polyethersulfone/polyetherethersulfone (PES/PEES) copolymers, at various PES/PEES ratios, were performed. The glass transition temperatures (T_g) were determined by DSC. Degradations were carried out in a thermobalance, under flowing nitrogen, in dynamic heating conditions from 35 °C to 650 °C. The initial decomposition temperatures (T_i) and the half decomposition temperatures (T_1/2) were directly determined by TG curves, while the apparent activation energies of degradation (E_a) were obtained by the Kissinger method. In addition, the complex viscosities (η^∗) of the molten polymers were determined in experimental conditions of linear viscoelasticity. T_g, E_a and η^∗ values increased linearly with PES% content, while T_i and T_1/2 values showed opposite behaviour. In every case both PES and PEES homopolymers felt outside linearity. The results obtained are discussed and interpreted, and compared with those of corresponding Cl-ended copolymers previously studied.     

Thermal and rheological behaviour of some random aromatic polyethersulfone/polyetherethersulfone copolymers

The thermal and rheological behaviour of seven random Cl-ended aromatic PES/PEES copolymers (M_n ≈ 9500 g mol⁻¹), at various PES/PEES repeating unit ratios, was studied. The glass transition temperatures (T_g), determined by DSC experiments, showed a dependence on copolymer composition significantly different from the ideal linear behaviour expected on the basis of Fox equation. Degradations were carried out in the scanning mode, under flowing nitrogen, in the temperature range 35-650 °C and a single degradation stage was observed for all copolymers. The initial decomposition temperatures (T_i) and the half decomposition temperatures (T_1/2) were directly determined by TG curves, while the apparent activation energies of degradation (E_a) were obtained by the Kissinger method. In addition, the complex viscosity (η^∗) of molten copolymers was determined in experimental conditions of linear viscoelasticity. T_i, T_1/2, E_a, and η^∗ values were depending on copolymer composition, showing a trend similar to that of T_g values. The results obtained were discussed and interpreted.     

Synthesis and characterization of a new network polymer electrolyte containing polyether in the main chains and side chains

A new network polymer electrolyte matrix with polyether in the side chains and main chains was synthesized by the azo-macroinitiator method and urethane reaction. The macroinitiator, polymer and network polymer were confirmed by Fourier-transform infrared (FT-IR) spectroscopy and ¹H NMR. FT-IR was also used to study the environment of lithium ions doped in these network polymer electrolytes. Three important groups are considered: N-H, carbonyl, and ether groups. The thermal properties of the polymer electrolytes were measured by differential scanning calorimetry and thermogravimetric analysis. The T_g value of this polymer is less than that of a general comb-like polymer. Added lithium ions interact with the oxygen atoms on ether groups, causing the T_g of the polymer electrolyte to increase. Moreover, the interaction between lithium ions and ether groups decreases the decomposition temperature of the polymer. The conductivity measured by AC impedance reached a maximum of 10⁻⁴ S cm⁻¹. A plot of conductivity vs. temperature fit the Vogel-Tamman-Fulcher equation, indicating that ionic mobility in this network polymer electrolyte is coupled to segmental chain movements.     

Homopolymer and copolymers of 4-nitro-3-methylphenyl methacrylate with glycidyl methacrylate: Synthesis, characterization, monomer reactivity ratios and thermal properties

The novel methacrylic monomer, 4-nitro-3-methylphenyl methacrylate (NMPM) was synthesized by reacting 4-nitro-3-methylphenol dissolved in ethyl methyl ketone (EMK) with methacryloyl chloride in the presence of triethylamine as a catalyst. The homopolymer and copolymers of NMPM with glycidyl methacrylate having different compositions were synthesized by free radical polymerization in EMK solution at 70 ± 1 °C using benzoyl peroxide as free radical initiator. The homopolymer and the copolymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility tests were tested in various polar and non-polar solvents. The molecular weight and polydispersity indices of the copolymers were determined using gel permeation chromatography. The glass transition temperature of the copolymers increases with increase in NMPM content. The thermogravimetric analysis of the polymers performed in air showed that the thermal stability of the copolymer increases with NMPM content. The copolymer composition was determined using ¹H NMR spectra. The monomer reactivity ratios were determined by the application of conventional linearization methods such Fineman-Ross (r₁ = 1.862, r₂ = 0.881), Kelen-Tudos (r₁ = 1.712, r₂ = 0.893) and extended Kelen-Tudos methods (r₁ = 1.889, r₂ = 0.884).     

Synthesis and characterization of amorphous poly(ethylene terephthalate) copolymers containing bis[4-(2-hydroxyethoxy)phenyl]sulfone

Poly(ethylene terephthalate) copolymers (abbreviated as PETS) that contain bis[4-(2-hydroxyethoxy)phenyl]sulfone (BHEPS) were prepared from dimethyl terephthalate (DMT), ethylene glycol (EG) (5-95%) and BHEPS (5-95%). The compositions and microstructures of the copolyesters were determined by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, respectively. The thermal behaviors were studied over the entire range of copolymer compositions, using X-ray analysis, differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The molecular weights, optical characteristics and tensile properties of these polymers were also determined. Experimental results indicated that the copolymers had a random microstructure. The intrinsic viscosities of the copolymers ranged from 0.65 to 0.69 dL/g. The copolyesters with BHEPS of <10 mol% were crystallizable, whereas the copolyesters with BHEPS of ?10 mol% were amorphous. Incorporating BHEPS affected the glass-transition temperature (T_g) values of those polymers, from about 81 °C for PETS₅ to 126 °C for PETS₉₅. The optical transmissions exceeded 86% for λ = 400 nm for all of the amorphous polyesters. The tensile modulus and strength of the copolyesters increased with BHEPS. However, they also became brittle and their elongation at break decreased.     

Preparation of 4(5)-vinylimidazole-co-acrylic acid copolymer and thermal performances related to applicability as PEM fuel cells

A series of acrylic acid and 4(5)-vinylimidazole copolymers for a non-hydrous proton transferring membrane used in polymer electrolyte membrane for fuel cell (PEMFC) are reported. The feed ratio of each monomer results in the variation of copolymer as evaluated by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (¹H-NMR). Differential scanning calorimeter and thermal gravimetric analyzer confirm the thermal properties of copolymer films with T_g at 105-177 °C and T_d above 230 °C. The simultaneous analysis of wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) suggests the thermal performance about the decrease in domain size as a consequence of the loss of moisture content in the membrane and the increase in domain size as a consequence of chain mobility after T_g. The proton conductivities under anhydrous condition of the copolymer membranes are in the range of 10⁻² S/cm even up to 120 °C.     

Synthesis and characterization of new polymer systems containing very bulky tris(trimethylsilyl)methyl substituents as side chains

The 4-chloromethyl styrene (CMS) was copolymerized with different styrenic monomers such as methyl styrene, 4-methoxy styrene and α-methyl styrene by free radical polymerization method at 70 ± 1 °C using α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator and the copolymers I, II and III collected respectively. The very bulky tris(trimethylsilyl)methyl {trisyl} substituents were covalently attached to the obtained copolymers with replacement of all the chlorine atoms in CMS units. The polymers, obtained in quantitative yields, were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy; differential scanning calorimetry (DSC) and GPC studies. All the polymers containing trisyl groups showed a high glass transition temperature (in the range 150-190 °C) in comparison with copolymers I-III (in the range 90-95 °C). The increase of the glass transition temperature reflects the substantial increase in rigidity of new polymers bearing very bulky substituents in side chains.     

Radical solution copolymerisation of vinylidene fluoride with hexafluoropropene

The radical copolymerisation in solution of vinylidene fluoride (or 1,1-difluoroethylene (VDF)) with hexafluoropropylene (HFP) initiated by di-tert-butyl peroxide is presented. A series of eight copolymerisation reactions was investigated with initial [VDF]_o/[HFP]_o molar ratios ranging from 5.0/95.0 to 85.2/14.8. Both co-monomers copolymerised in this range of copolymerisation. Moreover, only VDF homopolymerised in these conditions. The copolymer compositions of these random-type copolymers were calculated by means of ¹⁹F NMR spectroscopy which allowed the respective amount of each monomeric unit in the copolymer to be quantified. The Tidwell and Mortimer method led to the assessment of the reactivity ratios, r_i, of both co-monomers showing a higher incorporation of VDF in the copolymer (r_HFP = 0.12 ± 0.05 and r_VDF = 2.9 ± 0.6 at 393 K). Alfrey-Price's Q and e values of HFP were calculated to be 0.002 (from Q_VDF = 0.008) or 0.009 (from Q_VDF = 0.015) and +1.44 (versus e_VDF = 0.40) or +1.54 (versus e_VDF = 0.50), respectively, indicating that HFP is an electron-accepting monomer. The thermal properties of these fluorinated copolymers were also determined. Except for those containing a high amount of VDF, they were amorphous. Each showed one glass transition temperature (T_g) only, and from known laws of T_g, that of the homopolymer of HFP was assessed. It was compared with that obtained from the literature after extrapolation and is discussed.     

Phase behavior of biodegradable amphiphilic poly(l,l-lactide)-b-poly(ethylene glycol)-b-poly(l,l-lactide)

This study describes the miscibility phase behavior in two series of biodegradable triblock copolymers, poly(l-lactide)-block-poly(ethylene glycol)-block-poly(l-lactide) (PLLA-PEG-PLLA), prepared from two di-hydroxy-terminated PEG prepolymers (M_n = 4000 or 600 g mol⁻¹) with different lengths of poly(l-lactide) segments (polymerization degree, DP = 1.2-145.6). The prepared block copolymers presented wide range of molecular weights (800-25,000 g mol⁻¹) and compositions (16-80 wt.% of PEG). The copolymer multiphases coexistance and interaction were evaluated by DSC and TGA. The copolymers presented a dual stage thermal degradation and decreased thermal stability compared to PEG homopolymers. In addition, DSC analyses allowed the observation of multiphase separation; the melting temperature, T_m, of PLLA and PEG phases depended on the relative segment lengths and the only observed glass transition temperature (T_g) in copolymers indicated miscibility in the amorphous phase.     

Synthesis,characterization, and spectroscopic studies of tetradentate Schiff base chromium(III) complexes

Eight chromium(III) complexes of tetradentate Schiff bases have been prepared in situ by condensing of a substituted salicylaldehyde compound with ethylenediamine. These were characterized by elemental analysis, m.p., IR, molar conductivity, magnetic moment measurements, and electronic spectra. The free ligands were also characterized by ¹H and ¹³C NMR spectra. The ¹³C NMR spectra are discussed in terms of possible substituent effects. The IR and electronic spectra of the free ligand and the complexes are compared and discussed. The electrospray ionization (ESI) mass spectra of four free ligands and their complexes were measured. The deconvolution of the visible spectra of the complexes, C_2v symmetry, in DMSO yields three peaks at ca. 15 600–17 600, 18 400–20 400 and 20 000–23 100, and are assigned to the three d–d transitions, ⁴B_1g → ⁴E_g(⁴T_2g); ⁴B_1g → ⁴B_2g(⁴T_2g); ⁴B_1g → ⁴E_g(⁴T_1g), respectively. The complexes showed magnetic moment in the range of 3.5–4.2 BM which corresponds to three unpaired electrons.     

Conductivity and thermal behavior of proton conducting polymer electrolyte based on poly (N-vinyl pyrrolidone)

The polymer electrolytes based on poly N-vinyl pyrrolidone (PVP) and ammonium thiocyanate (NH₄SCN) with different compositions have been prepared by solution casting technique. The amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The shift in T_g values and the melting temperatures of the PVP-NH₄SCN electrolytes shown by DSC thermo-grams indicate an interaction between the polymer and the salt. The dependence of T_g and conductivity upon salt concentration have been discussed. The conductivity analysis shows that the 20 mol% ammonium thiocyanate doped polymer electrolyte exhibit high ionic conductivity and it has been found to be 1.7 × 10⁻⁴ S cm⁻¹, at room temperature. The conductivity values follow the Arrhenius equation and the activation energy for 20 mol% ammonium thiocyanate doped polymer electrolyte has been found to be 0.52 eV.     

Preparation and thermal properties of diglycidylether sulfone epoxy

A diglycidylether sulfone monomer (sulfone type epoxy monomer, SEP) was prepared from bis(4-hydroxyphenyl) sulfone (SDOL) and epichlorohydrin without any NaOH or KOH as basic catalyst. FT-IR, ¹H NMR, ¹³C NMR and mass spectroscopic instruments were utilized to determine the structure of the SEP monomer. The cured SEP epoxy material exhibited not only a higher T_g (163.81 °C) but also a higher T_g than pristine DGEBA (from 111.25 °C to 139.17 °C) when the SEP monomer moiety had been introduced into the DGEBA system. The thermal stability of cured epoxy herein was investigated by thermogravimetric analysis (TGA). The results demonstrated that the sulfone group of the cured SEP material decomposed at lower temperatures and formed thermally stable sulfate compounds, improving char yield and enhancing resistance against thermal oxidation. Additionally, the IPDT and char yield of the cured SEP epoxy (IPDT = 1455.75, char yield = 39.67%) exceeded those of conventional DGEBA epoxy (IPDT = 667.27, char yield = 16.25%).     

The influence of chain rigidity on the thermal properties of some novel random copolyethersulfones

Some random low molar mass (M_n ≈ 9000 g mol⁻¹) poly(ethersulfoneethersulfone)/poly(ethersulfoneethersulfonebiphenylsulfone) P(ESES)/P(ESESBS) copolymers, with various (25%, 50% and 75%) ESESBS units contents, were synthesized to obtain compounds with higher chain rigidity than PES. The thermal characterization of the prepared copolymers, as well as that of corresponding P(ESES) and P(ESESBS) homopolymers, was performed, and all investigated parameters showed strong dependence on polymer composition.The glass transition temperature (T_g) was calorimetrically determined by DSC technique, and the obtained values increased linearly as function of ESESBS units percentage, thus indicating an increasing chain rigidity.Degradations were carried out in dynamic heating conditions, from 35 °C to 700 °C, in both flowing nitrogen and static air atmosphere, and the characteristic parameters of degradation were determined in order to draw useful information about the overall thermal stability of the studied compounds. The apparent activation energy of degradation (E_a) was obtained by the Kissinger method, and the values found increased linearly as a function of ESESBS content, while the temperature values at 5% mass loss (T_5%) showed an opposite linear trend. The results are discussed and interpreted.     

Synthesis and characterization of novel polyamides from new aromatic phosphonate diamine monomer

New aliphatic-aromatic and fully aromatic phosphonate polyamides were prepared by polycondensation reaction of our synthesized aromatic diamine: tetraethyl[(2,5-diamino-3,6-dimethylbenzene-1,4-diyl)dimethanediyl]bis(phosphonate) with the specific di-acylchloride (adipoyl chloride, isophthaloyl chloride and terephthaloyl chloride). The chemical structure of all samples were characterized by (¹H and ³¹P) NMR, MALDI-TOF MS, FT-IR tools, whereas their thermal properties were determined by DSC and TGA techniques. The phosponate polyadipamide (referred as PAP) is a semi-crystalline sample with a melting temperature at about 261 °C and glass transition (T_g) of 71 °C. All polymers show two thermal degradation steps in the temperature range 270-550 °C. Each polymer, independently its structure, shows the first maximum rate of thermal decomposition temperature (PDT) around 300-310 °C, which may be due to thermal degradation of phoshonate groups. MALDI-TOF spectra, beside the linear oligomers terminated with the specific groups expected in accord to the synthesis procedure, reveals the presence of cyclic oligomers in the polyadipamide and polyisophthalamide samples.