Copolymerization of poly(vinyl alcohol)‐graft‐poly(1,4‐dioxan‐2‐one) with designed molecular structure by a solid‐state polymerization method

Poly(vinyl alcohol)‐graft‐poly(1,4‐dioxan‐2‐one) (PVA‐g‐PPDO) with designed molecular structure was synthesized by a solid‐state polymerization. The solid‐state copolymerization was preceded by a graft copolymerization of PDO initiated with PVA as a multifunctional initiator, and Sn (Oct)₂ as a coininitiator/catalyst in a homogeneous molten state. The polymerization temperature was then decreased and the copolymerization was carried out in a solid state. The products prepared by solid‐state polymerization were characterized by ¹H NMR and DSC, and were compared with those synthesized in the homogeneous molten state. The degree of polymerization (D_p), degree of substitution (D_s), yield and the average molecular weight of the graft copolymer with different molecular structure were calculated from the ¹H NMR spectra. The results show that the crystallization process during the solid‐state polymerization may suppress the undesirable inter‐ or intramolecular side reactions, then resulting in a controlled molecular structure of PVA‐g‐PPDO. The results of DSC measurement show that the molecular structures determine the thermal behavior of the PVA‐g‐PPDO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3083–3091, 2006     

Poly(diarylsilmethylene)s,I. Synthesis and characterization

Poly(diarylsilmethylene)s with phenyl or tolyl substituents on Si atoms were synthesized by ring-opening polymerization of corresponding 1,1,3,3-tetraaryl-1,3-disilacyclobutanes, and were characterized by means of DSC, x-ray diffraction and melt viscosity measurements. Three preparative routes including catalytic and noncatalytic polymerization methods were examined to see differences in properties of the resulting polymers. The polymers thus obtained were crystalline and soluble in limited solvents such as diphenyl sulfone at tem-peratures above 250°C. Poly(diphenylsilmethylene) exhibited a melting temperature of about 350°C, whereas those of polymers with tolyl groups were observed in a temperature range between 310 and 330°C. The melt viscosity of the poly(diarylsilmethylene)s was measured to obtain insight into the molecular weights of the polymers, and the results indicated that the molecular weights are modifiable by varying the monomer-to-catalyst ratio when solution polymerization is employed. The DSC and x-ray studies were also carried out with focusing on the melting and crystallization behavior of these polymers. © 1995 John Wiley & Sons, Inc.     

Thermal analysis of the polymerization process on the surface of inorganic fillers

The thermal polymerization of pentabromobenzyl (mono)acrylate (PBB-MA) on the surface of the inorganic fillers Mg(OH)₂ and CaCO₃ was studied. FTIR spectroscopy and extraction of the polymer in bromobenzene show that polypentabromobenzyl acrylate (PBB-PA) was mostly grafted on the surface of Mg(OH)₂. Thermal analysis (TG, DSC, isothermal DSC (IDSC)) demonstrated an increase in polymerization starting temperature, and differences in polymerization enthalpy and apparent activation energy when an inorganic filler is added. These differences depend on the chemical composition of the filler used.The authors acknowledge valuable discussions with Prof. S. Yariv. The authors are also grateful to Berecha Foundation (Geneva) for the financial support of this work.     

Synthesis and characterization of poly(N-acyl or N-aroyl ethylenimines) containing various pendant functional groups. I. Copolymers with pendant olefin groups

Decenyl (D) and heptyl (H) oxazolines were copolymerized in o-dichlorobenzene solvent using methyl 4-nitrobenzenesulfonate as an initiator. A series of decenyl/heptyl oxazolines random copolymers (or DH copolymers) with a total degree of polymerization of 100 and narrow molecular weight distribution were obtained. These copolymers are considered as the poly(N-acylethylenimine)s with allyl pendant groups randomly attached to the far end of their polymethylene, (SINGLE BOND)(CH₂)₇(SINGLE BOND), side chains. The polymers were characterized by NMR, FT–IR. Both DSC and x-ray diffractometer demonstrated that the polymers are highly crystalline. © 1996 John Wiley & Sons, Inc.     

Poly-Schiff bases. III. Synthesis and characterization of polyesterazomethines

Ten new polyesterazomethines have been synthesized by solution polycondensation of five different diamines with 4,4′-[terephthaloyloxy]bis-3-ethoxybenzaldehyde and 4,4′-[isophthaloyloxy]bis-3-ethoxybenzaldehyde using dimethylacetamide in the presence of anhydrous LiCL. Fibrous polymers were precipitated by pouring the solutions into water. The polymerization proceeds rapidly to give highly viscous solutions. The resulting polymers were characterized by viscosity measurement, IR, x-ray diffraction study, elemental analysis, and DSC study. ¹H-NMR spectra of some of the polymers were also recorded. The thermal stability of the polymers was evaluated by TGA and IGA study. Electronic spectra of the polymers were recorded in H₂SO₄. © 1996 John Wiley & Sons, Inc.     

Non-isothermal kinetics of free-radical polymerization of 2,2-dinitro-1-butyl acrylate

The free-radical bulk polymerization of 2,2-dinitro-1-butyl-acrylate (DNBA) in the presence of 2,2′-azobisisobutyronitrile (AIBN) as the initiator was investigated by DSC in the non-isothermal mode. Kissinger and Ozawa methods were applied to determine the activation energy (E _a) and the reaction order of free-radical polymerization. The results showed that the temperature of exothermic polymerization peaks increased with increasing the heating rate. The reaction order of non-isothermal polymerization of DNBA in the presence of AIBN is approximately 1. The average activation energy (92.91±1.88 kJ mol ⁻¹) obtained was smaller slightly than the value of E _a=96.82 kJ mol⁻¹ found with the Barrett method.     

Investigations of a series of PPDI-based polyurethane block copolymers. I. General morphology

The morphology of a series of segmented polyurethane block copolymers is characterized by x-ray scattering, differential scanning calorimetry (DSC), density measurements, and tensile studies. The materials contain hard segments formed from paraphenylene diisocyanate (PPDI) and flexible segments formed from poly(oxytetramethylene) (POTM) ranging in molecular weight from 650 to 2000. Four different molecular weight compositions were investigated, with the weight fraction of the hard segment (w_h) ranging from 0.14 to 0.33. The microphase structure has been examined using small-angle x-ray scattering, and the microphase transition zone thickness is estimated to be on the order of 1 nm. Oriented samples have been characterized with wide-angle x-ray scattering, and the flexible segment is shown to undergo stress-induced crystallization. DSC thermograms show flexible segment melting in the compositions containing the highest two molecular weights of the flexible segments. The hard segment thermal transitions were complex with a broad melting peak that varied with weight fraction and with a high temperature transition attributed to regions with hard segment lengths longer than the bulk of the hard segment component. There is an increase in tensile strength and initial modulus and decrease in elongation with increasing w_h. Density data suggest the existence of a multiphase system.     

Kinetic Study of the Thermal Polymerization Reactions between Diazide and Internal Diyne

The reaction kinetics between diazide(4,4′‐biphenyl dibenzyl azide) and internal diyne(bis[2‐(phenyl)ethynyl]dimethylsilane) was studied in this study by means of differential scanning calorimetry (DSC) and nuclear magnetic resonance spectra (¹H NMR). DSC was carried out to analyze the reaction in bulk polymerization condition, whereas ¹H NMR for solution reaction polymerization. The apparent activation energy (e_α) calculated by Kissinger's method was 90.83 kJ/mol, which was confirmed by Friedman's method, and 87.67 kJ/mol by ¹H NMR, respectively. The polymerization between the diazide and internal diyne was the second‐order reaction based on calculation from both of DSC and ¹H NMR.     

Preparation and characterization of poly(methyl methacrylate)/titanium oxide composite particles

Before polymerization, the introduction of double bonds onto the surface of the TiO₂ particles was achieved by the treatment of the TiO₂ particles with the silane-coupling agent. Via in-situ emulsion polymerization, the poly(methyl methacrylate) (PMMA)/titanium oxide (TiO₂) composite particles were prepared by graft polymerization of MMA from the surface of the modified TiO₂ particles. The structure of the obtained PMMA/TiO₂ composite particles was characterized using fourier transform infrared spectra (FT-IR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC) and size excluding chromatography (SEC). The morphology of the obtained PMMA/TiO₂ composite particles was observed by transmission electron microscope (TEM). The results of FT-IR and TGA measurements show that PMMA is successfully grafted from the surface of the TiO₂ particles and that the percentage of grafting and the grafting efficiency can reach 208.3% and 96.6%, respectively. At the same time, the TGA and DSC measurements indicate an enhancement of thermal stability. TEM images demonstrate a better dispersion of the TiO₂ particles in the composite latex. In addition, UV-visible absorption measurements show that the PMMA/TiO₂ composite particles can absorb over 95% UV light at 210–400 nm wavelength.     

Kinetics of polymerization of 1-octene with Mgcl2-supported Ticl4 catalysts

A number of TiCl₄ catalysts supported on MgCl₂ which was activated by the recrystallization method using different alcohols were prepared with ethyl benzoate or dibutyl phthalate as the internal electron donor. All the catalysts were characterized by BET, x-ray diffraction, and hydrolysis–GC analysis. Kinetics of polymerization of 1-octene was studied with three of the above catalysts (having different internal electron donors) activated by AlEt₃. The rate of polymerization increased linearly with increasing temperature, and catalyst and monomer concentrations. From the Arrhenius plot, the overall activation energies of polymerization were determined and the dependence of rate on the AlEt₃ concentration could be explained by the Langmuir-Hinshelwood mechanism. ¹³C-NMR was used to study the effect of internal electron donors on the % isotacticity of poly(1-octene). The catalytic activities of all the catalysts were compared in 1-octene polymerization. © 1994 John Wiley & Sons, Inc.     

In situ synthesis of A3‐type star polymer/clay nanocomposites by atom transfer radical polymerization

A series of A₃‐type star poly(methylmethacrylate)/clay nanocomposites is prepared by in situ atom transfer radical polymerization (ATRP) initiated from organomodified montmorillonite containing quaternary trifunctional ATRP initiator. The first order kinetic plot shows a linear behavior, indicating the controlled character of the polymerization. The resulting nanocomposites are characterized by spectroscopic (XRD), thermal (DSC and TGA), and microscopic (TEM) analyses. The exfoliated nanocomposite has been obtained when polymerization was conducted with 1% of organic clay loading. Thermal analyses show that all nanocomposites have higher glass transition values and thermal stabilities compared to neat polymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5257–5262     

Synthesis and characterization of poly(diethylsiloxane) and its copolymers with different diorganosiloxane units

Poly(diethylsiloxane) and its copolymers with various kinds of R₁R₂SiO (R₁ = R₂ = methyl or phenyl, or R₁ = methyl and R₂ = phenyl) units have been prepared by the equilibrium polymerization of cyclosiloxanes. All the polymers have been characterized by ¹H and ²⁹Si NMR, gel permeation chromatography, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The results indicate that a random distribution of different units has been obtained in the structures of copolymers containing 50 mol % diethylsiloxane units content. DSC and DMA show that the presence of 2.5 mol % diphenylsiloxane units or 5.0 mol % methylphenylsiloxane units in the copolymer can disrupt the crystallinity and lead to noncrystalline copolymers with low glass‐transition temperatures (ranging from ?133 to ?137 °C according to DSC). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2722–2730, 2003     

Influence of molecular arrangement on the γ-ray-irradiation solid-state polymerization of 1-octadecyl vinyl ether with a characteristic polymorphism

The polymorphic behavior of 1-octadecyl vinyl ether was investigated by DSC and X-ray diffraction measurements under various temperatures. In DSC measurement of 1-octadecyl vinyl ether in the temperature range of −30 to approximately 50°C, four transition peaks were observed on heating, whereas three transition peaks appeared on cooling. The phase-transition behavior was investigated by the repeating scanning DSC measurements. It was concluded that this compound exhibited four crystalline modifications: α, sub α, β₀, and β₁. It was confirmed by the temperature-controlled X-ray diffraction measurement that these phase transitions are attributed to the change of crystal systems from hexagonal packing (α form) to a distorted orthorhombic (O⟂′) system (β₁ form) via orthorhombic (O⟂) (sub α form) and intermediate β₀ form, although the β₀ form has not yet been clarified. In the γ-ray-irradiation solid-state polymerization for these crystal forms of this compound, the polymerizability of the sub α form is higher than that of other forms, and that of the α form is lowest. The polymerizability demonstrated an unusual increase at a temperature of −83.6°C, probably because the cationic polymerization mechanism is dominant over that of the free radical. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3845–3853, 1999     

Polymerization of N-Vinylcaprolactam and Characterization of Poly(N-Vinylcaprolactam)

Poly(N-vinylcaprolactam), PNVCL, is a nonionic, nontoxic, water soluble, thermally sensitive and biocompatible polymer. It contains hydrophilic carboxylic and amide groups with hydrophobic carbon-carbon backbone suitable for biomedical applications. In this study, N-vinylcaprolactam was polymerized by free radical polymerization at 50, 60 and 70°C. The synthesized polymers were white powder, soluble in water and common organic solvents. The percent conversion vs. time plot is almost linear up to about 60% conversion without induction period. The activation energy of polymerization was calculated as 108.4 kJ/mol from the Arrhenius plot. FTIR and NMR results showed that polymerization takes place by opening of carbon-carbon double bond without any change in the caprolactam ring. Polymer was characterized by FTIR, ¹H-NMR and ¹³C -NMR, DSC, TGA and XRD techniques. The DSC thermogram of monomer has shown a melting point at 37.3°C. The polymer has T_g value at 1.8°C and softening temperature at 68.8°C. It was determined from the X-Ray powder pattern that the polymerization proceed in the b-crystallographic axis direction.     

Synthesis and crystallization behaviors of poly(styrene-b-isoprene-b-ε-caprolactone) triblock copolymers

The triblock copolymers, poly(styrene-b-isoprene-b-ε-caprolactone)s (PS-b-PI-b-PCL) have been synthesized successfully by combination of anionic polymerization and ring-opening polymerization. Diblock copolymer capped with hydroxyl group, PS-b-PI-OH was synthesized by sequential anionic polymerization of styrene and isoprene and following end-capping reaction of EO, and then it was used as macro initiator in the ring-opening polymerization of CL. The results of DSC and WAXD show big effect of amorphous PS-b-PI on the thermal behaviors of PCL block in the triblock copolymers and the lower degree of crystalline in the triblock copolymer with higher molecular weight of PS-b-PI was observed. The real-time observation on the polarized optical microscopy shows the spherulite growth rates of PCL₂₇, PCL₃₂₈ and PS-b-PI-b-PCL₃₄₄ are 0.71, 0.46 and 0.07 μm s⁻¹, respectively. The atomic force microscopy (AFM) images of the PS₉₀-b-PI₆₆-b-PCL₂₈ show the columns morphology formed by it’s self-assembling.     

In situ Polymerization of Nanocomposites by TpTiCl2(Et) System: UHMWPE Filled with Carbon Nanotubes

Summary: Nanocomposites of ultra-high molecular weight polyethylene (UHMWPE) filled with multi-walled carbon nanotubes (CNT) were obtained by in situ polymerization of ethylene by TpTiCl₂Et. This novel catalytic complex activated with polymethylaluminoxane (P-MAO) (Al:Ti = 200) allowed to incorporate the CNT at different compositions (0,1-1 w/w %) into the UHMWPE matrix. The filler addition produced an important enhancement of the catalytic activity when it was compared to that of homogeneous ethylene polymerization carried out under the same experimental conditions (30 min; 1bar; 25 °C). This fact was attributed to in situ support of TpTiCl₂Et onto the CNT surface, which not only could induce the stabilization of the catalytic system but also allowed the growing of polymeric chains around the CNT structures. The characterization of these nanocomposites was carried out by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Thermal analysis showed that the incorporation of CNT (at the tested concentrations) did not produce changes in the polymer thermal stability, as revealed by the initial degradation temperature values. However, the CNT produced a nucleating effect in the crystallization of UHMWPE as observed by DSC, independently of the filler content. The crystallization temperature of the obtained nanocomposites increased and the crystallinity degree slightly increased as well.     

Polymerization of acenaphthylene by transition metal catalysts

The polymerization of acenaphthylene (ACN) was examined in the presence of the group V and VI transition metal salts such as WCl₆, MoCl₅, TaCl₅, and NbCl₅, as catalysts under various reaction conditions. These transition metal salts were found to be effective catalysts for the polymerization of ACN. The polymerization of ACN by WCl₆ in chlorobenzene proceeded at a high initial rate when the monomer to catalyst mole ratio was 200. In addition, it was observed that aromatic solvents generally were found to be superior to aliphatic solvents for both conversion and molecular weight. The structure of the resulting polymers was characterized by means of NMR, IR, UV, and x-ray diffraction. Emission properties were also investigated. Fluorescence emission spectra of the polymers obtained by WCl₆ as a catalyst varied strongly depending on the polymerization solvent. Thus, it appears that the polyacenaphthylene produced by WCl₆ was a different configuration dependent on the polymerization solvents used.     

Poly(thienyl‐phenylene)s with macromolecular side chains by oxidative polymerization of well‐defined macromonomers

Well‐defined polystyrene (PSt), poly(ε‐caprolactone) (PCL) or poly(2‐methyloxazoline) (POx) based polymers containing mid‐ or end‐chain 2,5‐ or 3,5‐dibromobenzene moieties were prepared by controlled polymerization methods, such as atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), or cationic ring opening polymerization (CROP). These polymers were subsequently modified by Suzuki type coupling reactions with 2‐thiophene boronic acid. The resulting polymers, containing a conjugated sequence with 2‐thienyl groups at the extremities, could be further used as macromonomers in chemical oxidative polymerization in the presence of anhydrous FeCl₃. Poly(thienyl‐phenylene)s having the respective PSt or PCL chains as lateral subtituents were obtained in this way. All the starting, intermediate, or final polymers were structurally analyzed by spectroscopic methods (¹H and ¹³C NMR, IR) and gel permeation chromatography (GPC) measurements. Thermal behavior of the macromonomers and final polymers was investigated by differential scanning calorimetry (DSC) analyses. Optical properties of the polymers were monitored by UV and fluorescence spectroscopy. The emission spectra of the polymers show a clear bathochromic shift of the λ_max emission in all the cases with respect to the monomers because of the extending of the conjugation length. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 848–865, 2007.     

PMMA/organomodified montmorillonite nanocomposites prepared by in situ bulk polymerization

Kinetics of the in situ bulk polymerization of methyl methacrylate in the presence of organomodified montmorillonite (MMT) was investigated using differential scanning calorimetry (DSC) and gravimetrically. Different amount and types of MMT under the trade names Cloisite were employed. Using DSC, the amount of heat released versus time, under isothermal conditions, was recorded, and eventually, the time evolution of polymerization rate and monomer conversion was calculated. Results on the variation of monomer conversion with reaction time were in good agreement to corresponding from the gravimetric measurements. The nanocomposites prepared were characterized with WAXD, TEM and FTIR, and their glass transition temperature, T _g, was measured with DSC. Depending on the added amount of nano-MMT, either exfoliated or intercalated structures were obtained. An enhancement of the polymerization rate with the presence of the nanoparticles was observed especially in the gel effect region. This was accompanied by a higher T _g and average molecular weight, as measured by GPC, of all nanocomposites compared to neat PMMA.     

Synthesis of polysiloxanes containing trifluoroethylene aryl ether groups: The effect of promoters

Polysiloxanes with high molecular weight (M_n > 100 000, M_w/M_n < 2.2) containing various quantity of trifluoroethylene aryl ether groups were prepared by anion ring opening polymerization (AROP) in the presence of promoters including N,N‐dimethylformamide (DMF) and N‐methyl pyrrolidone (NMP). The structures of monomers and polymers were characterized by FTIR and NMR. It was found that the addition of promoter could significantly increase the polymerization rate, decrease the polymerization temperature, and increase the molecular weight of the polymer. When DMF as the promoter, the optimal conditions for polymerization were as follows: The polymerization temperature is 100°C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 160:1. The optimal conditions for polymerization using NMP as the promoter were as follows: The polymerization temperature is 75°C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 70:1, which indicated that NMP is more effective on AROP than DMF. Thermogravimetric analysis (TGA) showed that the polymer has good heat temperature resistance. Differential scanning calorimetry (DSC) showed that the introduction of NMP in bulk polymerization could improve the randomness of polymer structure, which leads to the disappearance of crystal peak and improve the low temperature resistance of polymer.