Solid-state 13C-NMR studies of the aging of poly(vinylidene fluoride)/poly(methyl methacrylate) blends

Solid state ¹³C-NMR was used to investigate the miscibility and subsequent separation of solution-cast blends of poly(vinylidene fluoride) (PVF₂) and poly(methyl methacrylate) (PMMA) with aging for a range of compositions. It was found that one amorphous phase and intimate mixing of the polymer chains in this phase existed for all compositions of the blends, even after 2 months of aging at room temperature as determined by the proton spin lattice relaxation time T_1ρH in the rotating frame, and the time constant T_CH for transfer of magnetization. The T_1ρH is sensitive to the spatial homogeneity of the blend via spin diffusion and would indicate the presence of phases or domains in the amorphous component of the blend larger than approximately 19 Å. The T_CH is proportional to the inverse sixth power of the interatomic distances needed for transfer of magnetization from proton to carbon and would be sensitive to a separation of polymer chains in the amorphous phase with aging on the order of 4–5 Å. There was an increase of the T_1ρH and T_CH values with aging, indicating that a subtle separation between unlike chains in the amorphous phase was occurring although a single amorphous phase was present.     

Study on sequence distribution of segmented poly(urethane urea)s by 13C-NMR spectroscopy: Effect of polymerization procedures

The segmented poly(urethane urea) copolymers were synthesized by one- and two-step polymerization procedures. The copolymers were based on 4,4′-diphenylmethane diisocyanate, 3,5-diethyltoluene diamine, and ethylene oxide-capped poly(propylene oxide) diol. The mean sequence lengths of polyurethane soft block and polyurea hard block as well as the sequence distribution of the hard block in the copolymers were estimated from the signals of aromatic carbons in ¹³C-NMR spectra. The results indicated that two-step polymerization led to longer mean sequence lengths and broader hard block sequence distribution than one-step polymerization did. © 1996 John Wiley & Sons, Inc.     

Stereoregularity of poly(2-vinylpyridine) determined by 1H-NMR and 13C-NMR spectroscopy

In order to determine the stereoregularity of poly(2-vinylpyridine), 2-vinylpyridine-β,β-d₂ was synthesized. The ¹H-NMR spectra of the deuterated polymer in D₂SO₄ and o-dichlorobenzene solutions showed three peaks, which were assigned to triad tacticities. Since the absorptions of heterotactic and syndiotactic triads of methine protons overlap those of methylene protons in nondeuterated polymers, only isotactic triad intensities can be obtained from the ¹H-NMR spectra of nondeuterated poly(2-vinylpyridine). The ¹³C-NMR spectra of poly(2-vinylpyridine) were obtained in methanol and sulfuric acid solutions. In methanol solution the absorption was split into three groups, which cannot be explained by triads, and in sulfuric acid solution several peaks were observed. These splittings may be due to pentad tacticity. The results show that poly(2-vinylpyridine) obtained by radical polymerization is an atactic polymer.     

Preparation of telechelic oligomers by controlled thermal degradation of isotactic poly(1-butene) and poly(propylene-ran-1-butene)

It was found that telechelic isotactic oligo(1-butene) and telechelic oligo(propylene-ran-1-butene) could be isolated as nonvolatile oligomers from polymer residues resulting from the thermal degradation of isotactic poly(1-butene) and poly(propylene-ran-1-butene), respectively. Their structures were determined by ¹H and ¹³C NMR with attention being paid to their reactive end groups. The maximum average number of terminal vinylidene groups per molecule (f_TVD) was 1.8, indicating that about 80 mol% were α,ω-diene oligomers having two terminal vinylidene groups. This useful new telechelic oligomer had a lower polydispersity than the original polymer, in spite of its lower molecular weight and T_m. The composition of end groups of nonvolatile oligomers obtained by thermal degradation of poly(propylene-ran-1-butene) could be explained by the differences in bond dissociation energy and activation energy of elementary reactions during thermal degradation, based on the monomer composition of the original polymer.     

The effect of plasma treatment on structure and properties of poly(1-butene) surface

This paper is focused on the chemical and morphology changes in the surface of poly(1-butene) (PB-1) generated by plasma treatment. The radio frequency capacitively coupled plasma (air, argon, argon then allylamine, argon containing ammonia and argon with octafluorocyclobutane) was used. Modified surface of PB-1 was characterized by contact angle measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. The surface hydrophilization by air and argon with ammonia plasmas was evaluated as most sufficient. Oppositely, a high level of hydrophobicity of PB-1 surface was reached by combination of argon with octafluorocyclobutane plasma. Upon plasma modification, hydrophilicity/hydrophobicity of treated surfaces remained stable within three days under air atmosphere and then values of contact angle slowly recovered to those of unmodified PB-1. However, morphology and surface chemical composition of plasma-modified samples remained generally unchanged during observed time. Changes in surface hydrophilicity/hydrophobicity of plasma-treated PB-1 were attributed to variance of conformation of the surface molecules.     

Photodegradation of isotactic poly(1-butene): Multiscale characterization

The effect of photodegradation in isotactic poly(1-butene) (PB-1) have been investigated using rheology, differential scanning calorimetry and infrared spectroscopy. Two commercially available grades of PB-1 with different average molecular weight were chosen. Specimens prepared by compression moulding were UV irradiated in the interval from 0 to 70 h. UV-induced changes in molecular structure have been followed by evolution of rheological properties, thermal properties and degradation by-products. Thermal analysis showed significant changes in crystallization behaviour influencing morphology and resulting thermal properties. Moreover it has been confirmed that the degradation significantly retards the phase transformation. Rheological measurement has been found as an effective method for determination of early stages of photodegradation of PB-1.     

Rheology of polypropylene/poly(ethylene-co-propylene) in-reactor alloy

The interfacial adhesion and molecular structure of an in-reactor polypropylene/ethylene propylene rubber alloy were studied with respect to the rheological behavior and final properties of the alloy. The polymer alloys have similar structural parameters but different impact properties. The samples were characterized by gel permeation chromatography, thermal analysis, rheological analysis and mechanical testing. Fractionation of samples showed that the quantities of components are the same. Gel permeation chromatography results showed that molecular weight distribution of all components were similar. Thermal analysis results showed that the crystal size of two samples was the same but the crystal contents were different. In studying the impact strength, it was revealed that a large difference exists between the two samples. The small amplitude oscillation rheometry indicates that the rheological parameters have a glaring difference in both samples that can be an evidence of interfacial adhesion in the in-reactor alloys having so many similar structural parameters.     

Analysis of the physical and mechanical properties of poly(1-butene) thermoplastic elastomer by the <Superscript>13</Superscript>C-NMR and DSC methods

In this paper, we compare the physical and mechanical properties of poly(1-butene) thermoplastic elastomer (PB-TPE), which was prepared by supported titanium catalyst using solution polymerization (S-PB) and bulk polymerization (B-PB). The S-PB possesses higher tensile strength and elongation at break than the B-PB. Through the analysis of the microstructure with ¹³C-NMR spectra and thermal property with DSC, it is found that S-PB had more crystallizable block in the main chain that leads to higher crystallinity than B-PB.     

Stereoregularity of fractionally crystallized poly(propylene oxide) samples by 13C-NMR spectroscopy

Several stereoregular poly(propylene oxide) (PPO) samples were synthesized employing either trimethyl aluminum hydrolyzates or Pruitt–Baggett type catalysts. Dilute isooctane solutions of these samples were fractionally crystallized by stepwise cooling from 333 K down to 273 K. The fractions which dissolve at 273 K were noncrystallizable and were further fractionated by GFC. The isolated fractions were characterized by ¹³C-NMR, DSC, and viscometry techniques. Both structural (head-to-head and tail-to-tail linkages) and steric (syndiotactic dyads) irregularities were found in otherwise isotactic chains and their abundance apparently increased as the melting point and the chain length of the fractions decreased.     

Physico-chemical studies on the photostabilization of poly(1-butene) film

Thin films of poly(1-butene) with and withouto-phenanthroline bis(1,3-diphenyl triazine-1-oxide)-cobal(II) [I] in the temperature range of 233–333° K have been degraded in air from a UV light of 253.7 nm. The changes in weight average molecular weights, degree of degradation, quantum yields, enthalpy and free energy of activation, and carbonyl and hydroperoxide contents, were followed as a function of the time of irradiation. The inhibition effect ofI is discussed on the basis of the luminescence and UV spectral data. The chelateI behaves both as a thermal and UV stabilizer due to a combination of different kinds of activity in the same molecule.     

Characterization of poly(carboxylic acid)/poly(ethylene oxide) blends formed through hydrogen bonding by spectroscopic and calorimetric analyses

The solid state of the complex between poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO), and that between poly(methacrylic acid) (PMAA) and PEO formed via hydrogen-bonding was studied by differential-scanning calorimetric (DSC) and by Fourier-transform infrared (FT–IR) spectroscopic measurements. Melting temperature T_m and the degree of the crystallinity X_c of PEO in the systems PAA (or PMAA)/PEO blends obtained from aqueous or dimethyl sulfoxide (DMSO) medium were measured in various unit mol % of PEO ([PEO]100/{[PAA(or PMAA)] + [PEO]}) where [ ] is the unit mole concentration. It was found that 50 unit mol % of PEO is a critical composition, which gives new evidence for the 1 : 1 complex formation between PAA (or PMAA) and PEO. From the FT–IR spectroscopic analysis in conjunction with DSC measurements we also found that the effects of solvent and of hydrophobic interaction (due to the α-methyl group of PMAA) are the important factors controlling the complexation in the solution and solid systems. These factors also affect the crystallization behavior and the microstructure of the PAA (or PMAA)/PEO blend in solid state.     

Effect of the montmorillonite cloisite 15A on the structure and properties of poly(1-butene)

The structure and properties of nanocomposites based on poly(1-butene) and the nanoclay Cloisite 15A are studied. The nanoclay introduced into poly(1-butene) (5 wt %) is an efficient additive that improves mechanical and thermal properties of poly(1-butene).     

Kinetics of photo-sensitized and photo-stabilized photo-degradation of isotactic poly(1-butene)

This investigation describes the results of the 3-(o-carboxyphenyl)-1-phenyltriazene-N-oxide sensitized and copper(II) bis-3-(o-carboxyphenyl)-1-phenyltriazene-N-oxide stabilized photo-degradation of isotactic poly(1-butene) film in air, at a temperature at which formation of volatiles is negligible and with a light intensity flux of 2·38 × 10^?9 einstein s^?1 cm^?2. The course of the degradation and stabilization was determined by means of light scattering and spectrophotometric techniques. The extent of photo-degradation was followed by carbonyl formation, gel content and activation energy. Infra-red, ultraviolet spectra and light scattering data have been employed to substantiate a mechanism of degradation.     

Stereoregularity of poly(α-methylvinyl alkyl ether)s determined by 1H- and 13C-NMR spectroscopy

α-Methylvinyl methyl ether, ethyl ether, and isobutyl ether were polymerized under various polymerization conditions and the structure of the polymers was determined by ¹H- and ¹³C-NMR spectroscopy. α-Methyl and β-methylene carbon spectra of poly(α-methylvinyl isobutyl ether) showed splitting and were analyzed by triad and tetrad sequences. β-Methylene carbon spectra of poly(α-methylvinyl ethyl ether) also showed splitting. When Eu(fod)₃ was added, α-methyl and methoxy proton spectra in benzene of poly(α-methylvinyl methyl ether) showed splitting assigned to triad tacticities. All the polymers obtained in polar solvents exhibited an increase in syndiotacticity. The polymerization mechanism is discussed.     

Poly(vinylalcohol)/poly(ethyleneglycol)/poly(ethyleneimine) blend membranes - structure and CO2 facilitated transport

Poly(vinylalcohol) (PVA)/poly(ethyleneimine) (PEI)/poly(ethyleneglycol) (PEG) blend membranes were prepared by solution casting followed by solvent evaporation. The effects of the blend polymer composition on the membrane structure and CO₂/N₂ permeation characteristics were investigated. IR spectroscopy evidenced strong hydrogen bonding interactions between amorphous PVA and PEI, and weaker interactions between PVA and PEG. DSC studies showed that PVA crystallization was partially inhibited by the interactions between amorphous PVA and PEI blend, in which PEG separated into nodules. The CO₂ permeability decreased with an increase in CO₂ partial pressure in feed gas, while the N₂ permeability remained constant. This result indicated that only CO₂ was transported by the facilitated transport mechanism. The CO₂ and N₂ permeabilities increased monotonically with the PEI content in the blend membranes, whereas the ideal selectivity of CO₂ to N₂ transport showed a maximum. When CO₂ is humidified, its permeability through the blend membranes is much higher than that of dry CO₂, but the change in permeability due to the presence of humidity is reversible.     

Transport and thermal properties of poly(ether imide)/acetylene-terminated monomer blends

Blends of an acetylene-terminated monomer (ATM) with a commercially available poly(etherimide) (PEI, Ultem™) were prepared, crosslinked, and characterized. Varying degrees of crosslinking were achieved through thermal treatment at 150–270°C. Incorporation of the uncrosslinked additive into the PEI resulted in reductions in the glass transition temperature, gas permeabilities and selectivities, and thermal stability. These behavior are consistent with antiplasticization of the polymer host by the ATM additive. Crosslinking of the actylene-terminated additive led to increases in thermal and chemical stability and improved gas selectivities as compared to the uncrosslinked blend. Gas transport properties are reported as a function of temperature. For the blend composition considered (9 wt% ATM in PEI), the fully crosslinked blend had transport properties which were essentially equivalent to the virgin PEI. Further, processing of the blend could be achieved in the same manner as for the virgin PEI. The resistance of the crosslinked blend to chemical dissolution or swelling was markedly improved as compared to PEI.     

Protection of isotactic poly(1-butene) at low temperature against ultraviolet irradiation

The photodegradation and stabilization of isotactic poly(1-butene) at 2537 Å in the presence and absence of 3-hydroxy-1,3-diphenyl triazine N-oxide (HPTO) were examined by light scattering and spectrophotometric techniques. The data have been processed to yield the heats of activation for the system. Monochromatic quantum yields of the photolysis of the polymer films in the temperature range 233–333 K were calculated. The inhibitive action and the optimum concentration of HPTO are discussed from the view point of the molecular weight change and the carbonyl and hydroperoxide contents. The incorporation of 0.7% of HPTO in the matrix of polymeric film afforded complete protection to the polymer from actinic deterioration.