Synthesis and characterization of novel octa-arm star-block thermoplastic elastomers consisting of poly (p-chlorostyrene-b-isobutylene) arms radiating from a calix[8]arene core

The synthesis and characterization of novel octa-arm star-blocks consisting of poly(p-chlorostyrene-b-isobutylene) (PpClSt-b-PIB) arms radiating from a calix[8]arene (C8) core are described. The synthesis was accomplished by living isobutylene (IB) polymerization induced by a novel octafunctional calix[8]arene derived initiator 1, followed by addition and living polymerization of p-chlorostyrene (pClSt). This sequential block copolymerization method allowed for precise molecular weight control of both polymeric blocks and thus gave rise to star-block thermoplastic elastomers (TPE) with an outstanding combination of mechanical and thermal properties, i.e., high tensile strengths (22 – 27 MPa) and elongations (∼500 %). Differential scanning calorimetry (DSC) indicated microphase separation into glassy PpClSt (T_g= 129°C) and rubbery PIB (T_g=−66°C) domains, and transmission electron microscopy (TEM) indicated that the PpClSt domains are dispersed in the PIB matrix. Received: 1 April 1998/Revised version: 1 June 1998/Accepted: 2 June 1998     

Synthesis and properties of nonlinear optical chromophores and polymers containing 6-nitroquinoline as π-electron acceptor

Summary Two nonlinear optical (NLO) methacrylate monomers, 2-methyl-acrylic acid 2-(ethyl-{4-[2-(6-nitro-quinolin-2-yl)-vinyl]-phenyl}-amino)-ethyl ester (5) and 2-methyl-acrylic acid 6-{3-[2-(6-nitro-quinolin-2-yl)-vinyl]-carbazol-9-yl}-hexyl ester (7) were newly synthesized and copolymerized with methylmethacrylate to give NLO polymers, P1 and P2. These polymers were well soluble in organic solvents and showed glass transition temperatures at 145 °C and 114 °C, respectively. The number average molecular weights (Mn) were 26,600 for P1 and 9,300 for P2. The SHG coefficients (d₃₃) of corona-poled films of P1 and P2 measured with 1.064 μm Nd-YAG laser were 32.2 pm/V and 17.6 pm/V, respectively. Received: 29 September 1998/Revised version: 7 December 1998/Accepted: 11 December 1998     

Synthesis of poly(N,N-dimethylcarbamoylmethylene) as a polymer homolog of N,N-dimethylacetamide

Summary A novel polymer homolog of N,N-dimethylacetamide (DMAc) having amide groups on all main chain carbons, poly(N,N-dimethylcarbamoylmethylene) 1, was prepared by heating poly(di-t-butyl fumarate) 2 at 180 °C for 2 hours followed by treatment with hexamethylphosphoramide at 180 °C for 5 hours. The structure of the obtained polymer 1 was confirmed by ¹H-, ¹³C-NMR and IR spectroscopy. The polymer 1 actually showed the properties based on its repeating structures. 1 had the amphiphilicity and was soluble both in protic and aprotic solvents. Furthermore, 1 showed the miscibility with commodity polymers such as poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(vinyl chloride). In comparison with another polymer homolog of DMAc, poly(2-methyl-2-oxazoline), the polymer 1 exhibited better miscibility with poly(N-vinylpyrrolidone). Received: 24 June 1999/Accepted: 19 July 1999     

Novel aprotic polar polymers 2. Miscibility of aliphatic polysulfoxides

Summary Miscibility of aliphatic polysulfoxides (1, 2) with other commodity polymers was examined by comparing glass transition temperature(s) (T_gs) of the mixture of these polymers with T_gs of the original polymers by differential scanning calorimetry. It was found that the aliphatic polysulfoxides had good miscibility with poly(2-methyl-2-oxazoline) or/and poly(N-vinylpyrrolidone). Received: 25 December 1997/Revised version: 23 February 1998/Accepted: 25 February 1998     

Synthesis of a star-shaped polymer having tris (β-diketonato)chromium(III) at the center core

Summary The metal-centered star-shaped polymer was prepared by coordination of p-(1,3-butanedionyl)-terminated poly(oxyethylene) with Cr(III) ion. The structure was confirmed by GPC analysis and IR spectra. The resulting polymer complex was well-soluble in various organic solvents and water. Received: 1 June 1998/Accepted: 9 July 1998     

Synthesis and properties of thermotropic compounds with two terminal mesogenic units and a central spacer Homologous series of polymethylene -α, ω-bis[4-(4'-n-hexyloxybenzoyloxy)benzoate]

SUMMARY A new series of aromatic esters with two terminal mesogenic units and a central spacer 1 together with the free rodlike mesogenic ester unit 2,was synthesized and studied. The mesogenic properties of these compounds were investigated by differential scanning calorimetry, polarizing microscopy and X-ray diffraction. Received: 10 March 1998/Revised version: 8 July 1998/Accepted: 8 July 1998     

Synthesis of highly crosslinked thermally stable poly(vinylethers) by free radical polymerization

Summary 2,4-Di-(2'-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 2,4-di-(2'-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3,4-di-(2'-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3,4-di-(2'-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of 2,4-di-(2'-vinyloxyethoxy)benzaldehyde (1) and 3,4-di-(2'-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Trifunctional vinyl ether monomers 2 and 4 were polymerized readily by free radical initiators to give optically transparent swelling poly(vinylethers) 5 and 6. Polymers 5 and 6 were not soluble in common organic solvents such as acetone and DMSO due to crosslinking. Polymers 5 and 6 showed a thermal stability up to 300°C in DSC thermograms. Received: 24 February 1998/Revised version: 7 April 1998/Accepted: 7 April 1998     

Synthesis and characterization of addition-type polyimides functionalized with diamine chromophore

Summary The Bismaleimide-Diamine Chromophore (2) prepolymers were prepared in acetone. The structure of the prepolymer was characterized. The prepolymer exhibited excellent film-forming quality and good solubility in low boiling point solvent. Thermal and NLO properties of the cured polyimides were evaluated. The chromophore content strongly influenced the thermal properties and order parameter Φ. Received: 21 July 1998/Revised version: 25 August 1998/Accepted: 28 August 1998     

Synthesis of poly(succinimide-amide) by acid-catalyzed polycondensation of L-aspartic acid and aromatic aminocarboxylic acid

Summary The polycondensations of L-aspartic acid (1) with aromatic aminocarboxylic acid, 4-aminobenzoic acid (2a), 4-aminophenylacetic acid (2b), 4-aminomethylbenzoic acid (2c), 4-(4-aminophenyl)butyric acid (2d), and 4-aminocinnamic acid (2e) were carried out using phosphoric acid as a catalyst. The obtained copolymers consiting of the succinimide and amide units, poly(succinimide-co-amide) (3), were soluble in DMF and DMSO except for that with 2e. The thermal properties differed with varying the 2 unit in 3, i.e., the T_gs of 3a–c (99 ∼ 138°C) were higher than those of 3d (81 ∼ 1 01°C), the apparent difference in the T_m between 3a–d did not observed, and the T_d decreased in the order of 3a, 3c > 3d > 3b. Received: 24 February 1998/Revised version: 3 April 1998/Accepted: 13 April 1998     

Novel non-alternating copolymers synthesized by spontaneous copolymerization of p-chlorophenylmaleimide with 2-methyl-2-oxazoline

Summary The copolymerization of p-chlorophenylmaleimide (1) as electrophilic monomer with 2-methyl-2-oxazoline (2) as nucleophilic monomer without initiator in solution under different experimental conditions was investigated. Copolymers were characterized by FT-IR and ¹H-NMR spectroscopy. The copolymer composition was determined from ¹H-NMR spectra. Molecular weights ranged between 1700 and 5400 g/mol by vapor pressure osmometry. Received: 27 September 1998/Revised version: 27 January 1999/Accepted: 28 January 1999     

Effect of 1-allyl-3,4-dimethoxybenzene on the copolymerization of propene and small amount of ethylene with the TiCl4/dibutylphthalate (DBP)/MgCl2 catalyst activated by Al(i-C4H9)3

Summary Copolymerization of propene and small amount of ethylene was conducted with the TiCl₄/DBP/MgCl₂-Al(i-C₄H₉)₃ catalyst in the presence and absence of 1-allyl-3,4-dimethoxybenzene(ADMB). Addition of ADMB caused a decrease in the ethylene content in copolymer with an increase in the activity. From a detailed analysis of the copolymers fractionated with boiling diethylether, it was found that the ADMB-containing system gives ether-soluble polymers with higher molecular weight and narrower molecular weight distribution as well as less content of regioirregular sequences of propene. The microstructures of the ether-soluble parts suggested that ADMB might accelerate the propene polymerization at the aspecific sites formed. Received: 24 June 1998/Revised version: 28 September 1998/Accepted: 26 October 1998     

Grafting phosphonated thiol on hydroxy telechelic polybutadiene

Summary An hydroxytelechelic polybutadiene (PBHT) of 1200 molecular weight has been modified by the phosphonated thiol HS-(CH₂)₃-PO(OC₂H₅)₂ (I). The thiol (I) was prepared in three steps: phosphonation of allyl bromide, addition of thioacetic acid and hydrolysis. The grafting rate of (I) on PBHT has been calculated by sulfur analysis and by ¹H NMR. The results confirmed that the 1,2 double bonds are 10 times more reactive than the 1,4. The method led to new macromolecular polyols containing between 3 and 5 % in weight of phosphorous. These new long polyols should be very interesting in order to prepare fire retardant polyurethane networks. Received: 16 April 1998/Revised version: 13 May 1998/Accepted: 10 June 1998     

Synthesis of polymer having β,β-triketone unit in the main chain and its copper (II) complex

Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl₃, DMF, and DMSO. The structure of the polymer was confirmed by ¹H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex. Received: 20 March 1998/Accepted: 17 April 1998     

Novel aprotic polar polymers 3. Synthesis and properties of poly(phenyl vinyl sulfoxide)

Summary Poly(phenyl vinyl sulfoxide) 1 was prepared by anionic polymerization and its properties as a polymer homolog of dimethyl sulfoxide (DMSO) were examined. Polysulfoxide 1 was found to have good miscibility with poly(vinyl acetate) as well as poly(2-methyl-2-oxazoline) and poly(N-vinylpyrrolidone) by comparing glass transition temperature(s) (T_gs) of the mixture of these polymers with T_gs of the original polymers by differential scanning calorimetry. Received: 4 March 1998/Accepted: 23 March 1998     

Effect of monolithic zirconia on the degree of conversion of two resin cements analyzed by FT-IR/ATR spectroscopy

Objective: This study aimed to evaluate the degree of conversion (DC) of two different resin cements polymerized under the monolithic zirconia specimens in different thicknesses and colors.

Material and methods: Partially stabilized monolithic zirconia blocks (inCoris TZI) were cut into three different thicknesses (0.5, 1.0, and 2.0 mm) and the specimens were divided into four color groups (A1, A2, A3, and A4). The light transmittance of each specimen was measured. Panavia F 2.0 or Variolink N resin cement was applied into teflon mold and irradiated using the light emitting diode curing unit for 20 s under monolithic zirconia specimen (n = 10). The resin cement specimens were stored at room temperature under dry conditions. The DC of each specimen was measured by Fourier transform infrared-attenuated total reflection (FT-IR/ATR) spectroscopy after the 1st and 10th day. Data were analyzed with two-way analysis of variance (ANOVA), two-way repeated measures ANOVA, three-way repeated measures ANOVA, and the Tukey least significant difference (LSD) tests (α = 0.05).

Results: The light-cure resin cement groups showed higher DC than the dual-cure resin cement groups (p < 0.05). The DC of both resin cements reduced with an increase in the thickness and darkening of the color of monolithic zirconia specimens. There was a statistically meaningful increase in the 10th-day values for dual-cure resin cement (p < 0.05), whereas there were no significant differences between the 1st- and 10th-day values for light-cure resin cement (p > 0.05).

Conclusion: The use of light-cure resin cement can be suggested for the luting of monolithic zirconia restorations.     

IRS study of ethylene polymerization catalyst SiO2/MAO/zirconocene

Summary Lewis acidic sites (LAS) of silica, modified with TMA and MAO samples differed by TMA content, have been characterized by IR spectroscopy (CO adsorption as probe molecule at 77 K). Two types of LAS were found on the surface of silica modified with MAO and TMA: M LAS of moderate strength (ν_CO= 2204−2212 cm⁻¹) and weak W LAS (ν_CO= 2194 cm⁻¹). The concentration of these acidic sites has been estimated. It was shown by IRS study Cp₂ZrMe₂ interacts both with W LAS and M LAS. Correlation between the amount of M LAS and the activity of ethylene polymerization has been found. Received: 13 October 1998/Revised version: 10 June 1999/Accepted: 10 June 1999     

An EPR study of polysaccharide copper(II) complexes in composite dextran/epichlorohydrin gels

Summary The EPR spectra of composite dextran and carboxymethyldextran gels were studied in order to identify the functional groups involved in copper(II) complexation depending on pH. The porous structure resulting from crosslinking of polymer chains of dextran, via epichlorohydrin, forces the immobilization of Cu²⁺ ions surrounded by different oxygen groups of the polymer gel matrix. The different polynuclear structures are postulated to be formed depending on the type of polysaccharide derivatives. The results indicate that carboxyl and deprotonated hydroxyl groups participate in the complex formation. Received: 30 January 1998/Revised version: 13 May 1998/Accepted: 10 June 1998     

Blend of chitosan acetate salt with poly(N-vinyl-2-pyrrolidone): Interaction between chain-chain

SUMMARY: Clear blends of chitosan acetate salt with poly (N-vinyl-2-pyrrolidone) (PVP) made from aqueous solutions look to be miscible on appearance. IR spectra investigated the carbonyl-hydroxyl hydrogen bonding between chain-chain in the blends and thus evidenced the compatibility of two polymers on a molecular level. The IR spectra, DSC also explored the interaction changing during the temperature increasing and indicated that a significant conformational change took place. Received: 1 June 1998/Revised version: 1 October 1998/Accepted: 13 October 1998     

Synthesis of novel polyamidoamine (PAMAM) side chain dendritic oligourethane architecture

Summary: A convenient approach to the synthesis of a novel side chain dendritic oligourethane (SCDOU) (1) derived from ester terminated polyamidoamine (PAMAM) dendritic diol (G 3.5) (1a) with 2,4-toluene diisocyanate (TDI) was reported. Polymerization was conducted in bulk by using the catalytic amount of dibutyl tindilaurate (DBTD). The PAMAM dendritic diol as well as the side chain dendritic polyurethane were thoroughly characterized by means of IR, NMR spectroscopy. Received: 13 June 2001/Revised version: 28 August 2001/Accepted: 3 September 2001     

Effect of adhesive type and composite viscosity on the dentin bond strength

Objectives: Evaluate the influence of composite resins viscosity and type of cure of the adhesive systems on the bond strength of composite resins submitted to artificial aging.

Methods: Dentin specimens (n = 240) were divided into 2 groups: Group GC: GrandioSO, and Group GF: GrandioSO Heavy Flow. These groups were subdivided into 6: FM: Futurabond M – light cured, FDCC: Futurabond Dual Cure – chemical cured, FDCL: Futurabond Dual Cure – light cured, CS3: Clearfil S3 – light cured, CDCC: Clearfil Dual Cure – chemical cured, and CDCL: Clearfil Dual Cure – light cured. Resin blocks were build up on the dentin surface. Half of samples on each group were cut to obtain resin/dentin sticks (1 × 1 mm). The other half was first submitted to thermomechanical aging. The dentin/resin sticks were submitted to microtensile bond strength test and the results were analyzed using three-way ANOVA and Tukey’s test (α = 5%).

Results: ANOVA showed significant influence for adhesive (p = 0.0000) and aging (p = 0.0001). No significant influence of the composite viscosity on bond strength was observed (ANOVA: p = 0.0861). For adhesive, the results of Tukey’s test (MPa) were CDCC: 13.44 (±5.13)a; FM: 14,01 (±2.71)a; CDCL: 14.51 (±4.98)a; FDCC: 18.66 (±7.13)b; CS3: 18.80 (±6.50)b; FDCL: 19.18 (±7.39)b. For aging: AGED: 14.99 (±6.32)a; NOT AGED: 17.87 (±5.97)b.

Conclusion: Composite resin viscosities did not influence on the bond strength. Type of cure of the adhesives had influence on the bond strength. Thermomechanical aging decreased the bond strength.