Synthesis and characterization of random copolymers of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate and 2,3-dihydroxypropyl methacrylate

Poly[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate)] [poly(solketal methacrylate) (PSMA)] was synthesized by free radical polymerization. By partial hydrolysis of the acetal group, random copolymers of SMA with 2,3-dihydroxypropyl methacrylate (DHPMA) were synthesized whereas complete cleavage lead to poly(2,3-dihydroxypropyl methacrylate) (PDHPMA). The copolymer composition was determined by ¹H NMR spectroscopy. FTIR spectroscopy indicates the synthesis of random copolymers with different degrees of hydrogen bonding as measured by a shift of the OH vibration bands. The glass transition temperature of the random copolymers increases linearly with increasing DHPMA content, resulting in a positive deviation from the Fox equation. The thermal degradation of both homopolymers and their random copolymers has been studied. Finally, the solution behaviour of the copolymers and PDHPMA in water studied by dynamic light scattering showed a strong tendency of the polymer chains to form clusters in the size range of 15-62 nm. The size and the kind of associating interactions within the clusters strongly depend on the copolymer composition.     

Quinone copolymerization. I. Reactions of p-chloranil,p-benzoquinone,and 2,5-dimethyl-p-benzoquinone with vinyl monomers under free-radical initiation

The free-radical copolymerization reactions of p-chloranil, p-benzoquinone, and 2,5-di-methyl-p-benzoquinone with vinyl monomers were studied. Reactions of p-chloranil with styrene yielded copolymers of approximately 1:1 composition under a variety of reaction conditions. A copolymer containing a block of 1:1 of styrene:p-chloranil and a block of polystyrene was prepared. Several styrene-like monomers copolymerized with p-chloranil to yield copolymrs possessing considerable amounts of incorporated quinone. p-Benzoquinone copolymerized with 1,3-butadiene and 2-vinyl-pyridine to yield copolymers of significant molecular weights. Reactions of 2,5-dimethyl-p-benzoquinone with vinyl monomers did not yield any isolable polymeric products.     

An Investigation of the Structure of Copolymers of lsobutylene and Diene Prepared by Initiation with VCI4 in the Dark and with Visible Light

¹H-NMR spectra of copolymers of isobutylene and 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene were investigated in connection with the elucidation of the formation of soluble and insoluble copolymers. For copolymers soluble in heptane, benzene, and CCI₄ it was found that the incorporation of diene into the polymer chain proceeds by 1,4-addition in the case of copolymerizations conducted both in the dark and with visible light using VC1₄ as initiator. The formation of a soluble and an insoluble copolymer is attributed to a different type of initiation, either with radical-cations of isobutylene, if soluble copolymers are formed, or with radical-cations of diene, if the arising copolymers are insoluble.     

Synthesis of PP graft copolymers via anionic living graft-from reactions of polypropylene containing reactive p-methylstyrene units

In this article, we discuss a new chemical route for preparing polypropylene (PP) graft copolymers containing a PP backbone and several (polar and nonpolar) polymer side chains, including polybutadiene, polystyrene, poly(p-methylstyrene), poly(methyl methacrylate), and polyacrylonitrile. The new PP graft copolymers had a controlled molecular structure and a known PP molecular weight, graft density, graft length, and narrow molecular weight distribution of the side chains. The chemistry involves an intermediate poly(propylene-co-p-methylstyrene) copolymer containing few p-methylstyrene (p-MS) units. The methyl group in a p-MS unit could be lithiated selectively by alkylithium to form a stable benzylic anion. Because of the insolubility of the PP copolymer at room temperature, the excess alkylithium could be removed completely from the lithiated polymer. By the addition of the anionically polymerizable monomers, including polar and nonpolar monomers, the stable benzylic anions in PP initiated a living anionic graft-from polymerization at ambient temperature to produce PP graft copolymers without any significant side reactions. The side-chain length was basically proportional to the reaction time and monomer concentration. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4176–4183, 1999     

Preparation of 1,3-dienyl organotrifluoroborates and their Diels-Alder/cross-coupling reactions

2-BF₃-substituted 1,3-butadienes with potassium and tetrabutyl ammonium counterions have been prepared in gram quantities from chloroprene via a simple synthetic procedure. The potassium salt of this new main group element substituted diene has been characterized by ¹H, ¹³C, ¹¹B, and ¹⁹F NMR and the tetra n-butyl ammonium salt was also characterized by X-ray crystallography. Diels-Alder reactions of these dienes with dienophiles such as ethyl acrylate, methyl vinyl ketone, and N-phenylmaleimide are reported as well as subsequent Pd-catalyzed cross-coupling reactions of those Diels-Alder adducts. 4-Phenyl-2-BF₃-substituted 1,3-diene was prepared by magnesium-halogen exchange from the corresponding 2-bromo and iodo dienes. The 4-phenyl-2-bromo-1,3-butadiene was also characterized by X-ray crystallography. 4-Phenyl-2-BF₃-1,3-butadiene was used in Diels-Alder/cross-coupling reactions and the product of a Diels-Alder reaction with N-phenylmaleimide followed by cross-coupling with 4-bromo-benzonitrile was also characterized by X-ray crystallography.     

Study on conformational transition of EVA random copolymer in selective solvent mixtures

The dilute solution property of ethylene-vinyl acetate (EVA) random copolymer in 1,2-dichloroethane/cyclohexane (DCE/CYH) selective solvent mixture has been studied by viscometry, light scattering, differential refractomertry and UV spectrophotometry. It was found that both ethylene- and viny1 acetate sequence associations of EVA random copolymer displayed in both DCE and CYH solvents respectively, especially in DCE. Disassociation appeared when the volume fraction of CYH in the DCE/CYH solvent mixture φ_c was from 0.6 to 0.8. However, in this region, the extreme values of the intrinsic viscosity [η], Huggins constant k^′, unperturbed dimension K_θ, refractive index increment dn/dc occurred, and a discontinuity behavior of the preferential adsorption coefficient λ^′ and UV spectra demonstrated. These phenomena were attributed to conformational transition of the EVA molecule in solution, which was caused by DCE and CYH selective solvents, respectively.     

Diazo reactions with unsaturated compounds: XI. Reactions of benzene-, p-methylbenzene-, and p-methoxybenzenesulfonyl-1,3-butadienes with arenediazonium chlorides and 1-aryl-3,3-dimethyl-1-triazenes

1-(p-Methylbenzene)-and 1-(p-methoxybenzenesulfonyl)-1,3-butadienes in aqueous acetone in the presence of copper(I) or copper(II) chlorides react with arenediazonium chlorides and 1-aryl-3,3-dimethyl-1-triazenes to form 1-(p-methylbenzene)-and 1-(p-methoxybenzenesulfonyl)-4-aryl-3-chloro-1-butenes, respectively. 1-(Benzenesulfonyl)-1,3-butadiene undergoes tarring under the same conditions.     

Aqueous solution properties of amphiphilic triblock copolymer poly(p-dioxanone-co-l-lactide)-block-poly(ethylene glycol)

A poly(ethylene glycol) (PEG)-based new amphiphilic block copolymer bearing the poly(p-dioxanone-co-l-lactide) (PPDO/PLLA) hydrophobic moieties was prepared. Depending on the copolymer composition and molecular weights, solubility of the polymeric samples in water was varied. Its diluted aqueous solution properties were studied by viscometry, dye solubilization, ¹H-NMR and dynamic light scattering. 1,6-Diphenyl-1,3,5-hexatriene solubilization and ¹H-NMR spectra carried out in CDCl₃ and D₂O were used to prove the existence of hydrophobic domains as the core of micelle. Average particle size of 60-165 nm with low polydispersity and lower negative zeta (ξ) potential of −3 to −14 mV were observed on the aqueous copolymer dispersion.     

Dependence of flory-Huggins χ parameters on the copolymer composition for solutions of poly(methyl methacrylate-ran-n-butyl methacrylate) in cyclohexanone

Intermolecular interactions in random copolymer systems depend on the copolymer composition as being observed as a miscibility window in the random copolymer blends. The copolymer composition dependencies of the Flory-Huggins χ parameter and the heats of mixing ▵H_M(∞) at infinite dilution were studied for the solutions of poly(methyl methacrylate-ran-n-butyl methacrylate) (MMAnBMA) in cyclohexanone (CHN). The copolymer composition dependencies of χ obtained from osmotic pressures and of ▵H_M(∞) measured with a microcalorimeter were concave curves. This suggests that the random copolymers MMAnBMA interact with CHN more attractively than do the homopolymers PMMA and PnBMA. This is caused by the repulsion effect between the MMA and nBMA segments. The equation-of-state theory extended to the random copolymer systems by us reproduced fairly well these thermodynamic properties. The χ parameter for the PMMA/PnBMA blends was calculated using the equation-of-state theory with the MMA/nBMA intersegmental parameters employed for the above random copolymer solutions in CHN. The χ value calculated thus was in satisfactory agreement with that obtained from the random copolymer solutions using the Flory-Huggins theory extended to multicomponent systems. © 1996 John Wiley & Sons, Inc.     

Relationships between chemical structures and solubility,diffusivity, and permselectivity of 1,3-butadiene and n-butane in 6FDA-based polyimides

The solubility, diffusivity, and permselectivity of 1,3-butadiene and n-butane in seven different polyimides synthesized from 2,2-bis (3,4-carboxyphenyl) hexafluoropropane dianhydride (6FDA) were determined at 298 K. The influence of chemical structures on physical and gas permeation properties of 6FDA-based polyimides was studied. Solubility of 1,3-butadiene in 6FDA-based polyimides can be described by a dual-mode sorption model. 1,3-Butadiene-induced plasticization is considered to be associated with the increasing permeabilities of 1,3-butadiene and n-butane and the decreasing permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system containing a high concentration of 1,3-butadiene. It was found that controlling the solubility of 1,3-butadiene in an unrelaxed volume in 6FDA-based polyimides is very important to maintain the high permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system. Changing the  C(CF₃)₂ linkage to a  CH₂ ,  O linkage, removing methyl substituents at the ortho position of the imide linkage, and changing the p-phenylene linkage to an m-phenylene linkage in the main chains in some 6FDA-based polyimides are effective to decrease fractional free volume and restrict the solubility of 1,3-butadiene in the unrelaxed volume of a polymer matrix. The 6FDA-based polyimides restricting the solubility of 1,3-butadiene in an unrelaxed volume exhibit high separation performance in the 1,3-butadiene/n-butane mixed gas system compared with conventional glassy polymers and, therefore, are potentially useful membrane materials for the separation of 1,3-butadiene and n-butane in the petrochemical industry. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2941–2949, 1999     

Quantum chemical study of the structure of tricyclic saturated hexafluoro-1,3-butadiene dimers

Results of a quantum-chemical study of the molecular structure of dimerization products of saturated 1,3-butadiene and hexafluoro-1,3-butadiene (tricyclo[3.3.0.0^2.6]octane, dodecafluorotricyclo[4.2.0.0^2.5]octane (I), and dodecafluorotricyclo[3.3.0.0^2.6]octane (II)) are presented. The calculated symmetry of the molecule of I in vacuum (C ₂) differs from its symmetry in the single crystal (C _b , XRD). The most stable of dimers (II) contains C-C bonds with a length of up to 1.573 Å and a four-atom cycle with angles of 82.3°.     

Oxygen permeability of biodegradable copolycaprolactones

Polycaprolactone is one of the biodegradable polymers with good drug permeability. In the present paper, polycaprolactone and three kinds of copolycaprolactone–polycaprolactone–poly(ethylene oxide)– polycaprolactone triblock copolymer (PCE), polycaprolactone/polycaprolactone‐poly(ethylene oxide)/polylactide tricomponents random block copolymer (PCEL) and polycaprolactone/poly(ethylene terephthalate) random block copolymer (PETCL)– were synthesized. The biodegradation behavior of these polymers were shown by degradation tests in vitro, ex vivo and in vivo. The oxygen permeabilities of these polymers were in the range of 10⁻¹⁰ ∼ 10⁻⁹ cm³ (STP) cm/cm² sec cm Hg. Copolymers PCE and PCEL displayed O₂ and N₂ permeability coefficients (PO₂/PN₂) ratios of about 9. The effects of composition and crystallinity of the copolymers on biodegradability and the oxygen permeability of the polymer were discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Characterization of a 4-miktoarm star copolymer of the (PS-b-PI)3 PS type by temperature gradient interaction chromatography

Temperature gradient interaction chromatography (TGIC) was applied for the separation of a complex miktoarm star copolymer which has one polystyrene (PS) arm and three polystyrene-b-polyisoprene (PS-b-PI) diblock copolymer arms. Such miktoarm star polymers are much more difficult to characterize than branched homopolymers since the byproduct, typically polymers with missing arm(s) or coupled products, have not only different molecular weights but also different compositions. TGIC was able to fully separate the byproducts, and the composition of the molecular species corresponding to the different separated elution peaks was determined by two methods, fractionation/NMR and multiple detection (UV and RI). A reasonable agreement between the results of the two methods was obtained. By using the composition found, the corresponding molecular weights were determined by multi-angle light scattering detection. Based on the composition and the molecular weight we were able to identify the structure of the different molecular species.     

Reaction-induced microphase separation in epoxy resin containing polystyrene-block-poly(ethylene oxide) alternating multiblock copolymer

Polystyrene-block-poly(ethylene oxide) alternating multiblock copolymer (PS-alt-PEO) was synthesized with the combination of atom transfer radical polymerization (ATRP) and Huisgen 1,3-dipolar cycloaddition (i.e., click chemistry). The copolymer has been characterized by means of Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The PS-alt-PEO alternating multiblock copolymer was incorporated into epoxy resin to investigate the behavior of reaction-induced microphase separation, which has been compared to the case of the thermosets containing PS-b-PEO diblock copolymer. The morphology of epoxy thermosets containing PS-alt-PEO alternating multiblock copolymer were investigated by means of atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS) and the nanostructures were detected in all the thermosetting blends investigated. In marked contrast to the case of the thermosets containing PS-b-PEO diblock copolymer, the thermosets containing PS-alt-PEO multiblock copolymer displayed disordered nanostructures, which have been interpreted on the basis of the restriction of the alternating multiblock topology of the block on the formation of the nanostructures via reaction-induced microphase separation.     

Effect of the copolymer composition on the K and a constants of the Mark–Houwink equation: Styrene–methyl methacrylate random copolymers

This article reports a study of the effect of composition in styrene–methyl methacrylate random copolymers on K and a constants in the Mark–Houwink equation. Copolymers with a variety of compositions and chain lengths were prepared through a controlled free‐radical copolymerization, with benzyl diethyldithiocarbamate and tetraethyl thiuram disulfide as iniferters. The synthesized products were analyzed with several techniques, including Fourier transform infrared, ¹H NMR, gel permeation chromatography, and viscometry. By relating the determined constants K and a of various copolymers to their composition, we found that the constant varied nonlinearly with the composition. The constant a decreased with increasing poly(methyl methacrylate) (PMMA) content in the copolymer molecule up to 60 wt %. After that, the constant increased with the PMMA content, reaching the value of the PMMA homopolymer. However, the constant K initially increased with the PMMA content up to a critical composition (60 wt %) and subsequently decreased with further increasing PMMA content. These results suggest that the molecular weight of a polystyrene–PMMA random copolymer of known composition cannot be approximated with a simple linear equation comprising the K and a values of each relevant homopolymers. The aforementioned trends are qualitatively discussed in relation to some possible sequential distribution in the copolymer molecules and the resulting conformation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 562–571, 2002; DOI 10.1002/polb.10119     

Hetero-Diels–Alder reactions of perfluoroalkyl thioamides with electron-rich 1,3-dienes: synthesis of new 2-aminosubstituted-3,6-dihydro-2H-thiopyrans and related compounds

Hetero-Diels–Alder reactions of perfluoroalkyl thioamides with electron-rich 1,3-dienes such as 2,3-dimethylbutadiene, isoprene or penta-1,3-diene gave a simple and efficient access to new 2-aminosubstituted-3,6-dihydro-2H-thiopyrans. Three different procedures were used depending on the nature of the polyfluoroalkyl chains (R_F=CF₃, (CF₂)_nCF₃, (CF₂)₄H) and on the nitrogen substituents of the thioamides (R¹, R²=H, p-Tol, morpholino, Ac). Moreover, cycloadditions of silyloxydienes (1- or 2-trimethylsilyloxy-1,3-butadiene and Danishefsky's diene) with N-acyl,N-tolyl trifluoromethylthioamides afforded in almost all cases the corresponding 3,6-dihydro-2H-thiopyrans or 3-oxo-tetrahydrothiopyrans. For non-symmetrical 1,3-dienes, the regio- and stereochemistry of the reactions were studied (especially using X-ray diffraction analysis) indicating a strong similarity with those reported for fluorinated thiocarboxyl derivatives. Finally, two silylated 3,6-dihydro-2H-thiopyrans underwent an unexpected base-induced ring contraction to give new 1,3-thiazolidin-4-ones.     

Interdiffusion measurements of modified poly(arylether sulfone)s using nuclear reaction analysis

The interdiffusion and miscibility behavior of three different types of modified poly(arylether sulfone)s with deuterated poly(arylether sulfone) is studied by depth profiling using the nuclear reaction D(³He, α)p. The diffusion coefficients are found to be in the range of 10⁻¹⁵ and 10⁻¹⁴ cm²/s at 195°C. A random copolymer of poly(arylether sulfone) containing 4,4-bis-(4′-hydroxyphenyl)valeric acid units is only partially miscible with deuterated poly(arylether sulfone) when the comonomer content is 8.8 mol %, whereas blends with comonomer contents of 1.7 and 4.5 mol % are miscible as indicated by complete interdiffusion. The transition from miscibility to immiscibility is caused by repulsive interactions of copolymer segments and can be explained in terms of a mean-field theory of random copolymer blends. Also, poly(arylether sulfone)s grafted with 0.4 wt % maleic anhydride or having pyromellitic anhydride endgroups are miscible with deuterated poly(arylether sulfone)s. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2083–2091, 1997     

Synthesis of conjugated (1E,3E)- and (1Z,3Z)-1,4-di(n-pyridyl) (or n-quinolyl)-1,3-butadienes from n-(2′-chloroethenyl)pyridine (or quinoline)

The homocoupling reaction between the conjugated n-(2-chloroethenyl)pyridine; n, 2-, 3- and 4- (or quinoline; n, 2- and 4-) mediated by zero-valent nickel complexes at room temperature affords to the corresponding 1,4-diaryl-1,3-butadiene, always as the 1E,3E stereoisomer. The yield in 1,4-diaryl-1,3-butadiene increases with the nickel catalyst and hence, the active zero-valent nickel catalyst is not regenerated during the homocoupling reaction.The stereospecific synthesis of (1Z,3Z)-1,4-di(4′-pyridyl)-1,3-butadiene stereoisomer was efficiently carried out by partial hydrogenation of the appropriate 1,4-di(4′-pyridyl)-1,3-butadiyne.     

Palladium(II) 3-iminophosphine (3IP) complexes: Active precatalysts for the intermolecular hydroamination of 1,2-dienes (allenes) and 1,3-dienes with aliphatic amines under mild conditions

The synthesis of alicyclic 3-iminophosphine ligands is extended to include a new framework incorporating a cyclohexenyl backbone with an N-aryl imino functionality (3IP^Ar). Accordingly, a series of palladium(II) complexes employing this new ligand have been synthesized and utilized in the intermolecular hydroamination of 3-methyl-1,2-butadiene (1,1-dimethylallene) and 2,3-dimethyl-1,3-butadiene with secondary amines. The complex [(3IP^Ar)Pd(allyl)]OTf displays excellent catalytic activity in these reactions, selectively producing allylic amine products in high conversion under mild conditions, with an improved rate relative to that observed for our previously reported catalysts. Further, the reactivity trends for the (3IP)Pd triflate systems prove to be complimentary to other known late transition metal based catalytic systems.     

Thermal isomerization and decomposition of 1,2-butadiene in shock waves

1,2-Butadiene diluted with Ar was heated behind reflected shock waves over the temperature and the total density range of 1100–1600 K and 1.36 × 10^?5 ? 1.75 × 10^?5 mol/cm³. The major products were 1,3-butadiene, 1-butyne, 2-butyne, vinylacetylene, diacetylene, allene, propyne, C₂H₆, C₂H₄, CH₄, and benzene, which were analyzed by gas chromatography. The UV kinetic absorption spectroscopy at 230 nm showed that 1,2-butadiene rapidly isomerizes to 1,3-butadiene from the initial stage of the reaction above 1200 K. In order to interpret the formation of 1,3-butadiene, 1-butyne, and 2-butyne, it was necessary to include the parallel isomerizations of 1,2-butadiene to these isomers. The present data were successfuly modeled with a 82 reaction mechanism. From the modeling, rate constant expressions were derived for the isomerization 1,2-butadiene = 1,3-butadiene to be k₃ = 2.5 × 10¹³ exp(?63 kcal/RT) s^?1 and for the decomposition 1,2-butadiene = C₃H₃ + CH₃ to be k₆ = 2.0 × 10¹⁵ exp(?75 kcal/RT) s^?1, where the activation energies, 63 kcal/mol and 75 kcal/mol, were assumed. These rate constants are only applicable under the present experimental conditions, 1100–1600 K and 1.23–2.30 atm. © 1995 John Wiley & Sons, Inc.