Effect of Solvent on the Radical Copolymerizability of Styrene with 3(2-Methyl)-6-methylpyridazinone

Abstract

The radical copolymerization of styrene (St, M₁) with 3(2-methyl)-6-methylpyridazinone (I, M₂) has been carried out in several p-substltuted phenols at 60 and 70°C. Monomer reactivity ratios (r₁) and activation parameters of copolymerization were found to be affected by phenols. The values of the activation energy (δδE?) and entropy (δδS?) increased with the increase of the interaction of I with the solvents. Linear relationships were observed between the [sgrave]-values of p-substituents of phenols and the values of log 1/r₁ and also of δδE? and δδS?. The radical copolymerization of St (M₁) with 6-substituted 3(2-methyl)-pyridazinone was also carried out.     

Polymerization of Styrene Initiated by 1,4-Dimethyl-1,4-bis(p-anisyl)-2-tetrazene

Abstract

The polymerization of styrene (St) initiated by 1,4-dimethyl-1,4-bis(p-anisyl)-2-tetrazene (1a) was studied kinetically in benzene. The polymerization proceeds through a radical mechanism. The rate of polymerization is proportional to [1a]^0.5 and [St]^1.0. The overall activation energy for the polymerization is found to be 81.2 kJ/mol within the temperature range of 65 to 80°C. The activation parameters for the decomposition of 1a at 70°C are k_d = 1.88 × 10^?5s^?1, δH? = 133.1 kJ/mol, and δS? = 29.9 J/mol·deg.     

Polymerization of Methyl Methacrylate in the Presence of Imidazole Derivatives. Kinetics and Polymer Structure

The kinetics of the polymerization of methyl methacrylate (MMA) in the presence of imidazole (Im), 2-methylimidazole (2MIm), or benz-imidazole (BIm) in tetrahydrofuran (THF) at 15–40°C was investigated by dilatometry. The rate of polymerization, R_p , was expressed by R_p = k[Im] [MMA]², where k = 3.0 × 10^?6 L²/(mol² s) in THF at 30°C. The overall activation energy, E_a , was 6.9 kcal/mol for the Im system and 7.3 kcal/mol for the 2MIm system. The relation between logR_p and 1 T was not linear for the BIm system. The polymers obtained were soluble in acetone, chloroform, benzene, and THF. The melting points of the polymers were in the range of 258–280°C. The ¹H-NMR spectra indicated that the polymers were made up of about 58–72% of syndiotactic structure. The polymerization mechanism is discussed on the basis of these results.     

Surfacial modification of polymer powders as drug carriers

Preparation of warfarin methacrylate(WaMA) was carried out by esterification of warfarin as thromboembolism drug with methacryloyl chloride. Radical copolymerization of WaMA with 1-vinyl-2-pyrrolidone(VPr) was carried out in 1,4-dioxane at 60°C using 2,2′-azoisobutyronitrile as initiator. The surfacial modification of the copolymer powders was achieved using the freeze-drying by dissolving the copolymer in benzene and micellation by benzene-in-water and water-in-benzene systems. The hydrolysis of the copolymer including the drug was investigated under mild condition from a view point of released rate of the drug.     

Numerical analysis for a crack in piezoelectric material under impact

In this paper, a numerical analysis of impact interfacial fracture for a piezoelectric bimaterial is provided. Starting from the basic equilibrium equation, a dynamic electro-mechanical FEM formulation is briefly presented. Then, the path-independent separated dynamic J integral is extended to piezoelectric bimaterials. Based on the relationship of the path-independent dynamic J integral and the stress and electric displacement intensity factors, the component separation method is used to calculate the stress and electric displacement intensity factors for piezoelectric bimaterials in this finite-element analysis. The response curves of the dynamic J integral, the stress and electric displacement intensity factors are obtained for both homogeneous material (PZT-4 and CdSe) and CdSe/PZT-4 bimaterial. The influences of the piezoelectricity and the electro-mechanical coupling factor on these responses are discussed. The effects of an applied electric field are also discussed.     

Tandem trimer pyrrole–imidazole polyamide probes targeting 18 base pairs in human telomere sequences

The binding of molecules to specific DNA sequences is important for imaging genome DNA and for studying gene expression. Increasing the number of base pairs targeted by these molecules would provide greater specificity. N-Methylpyrrole–N-methylimidazole (Py–Im) polyamides are one type of such molecules and can bind to the minor groove of DNA in a sequence-specific manner without causing denaturation of DNA. Our recent work has demonstrated that tandem hairpin Py–Im polyamides conjugated with a fluorescent dye can be synthesized easily and can serve as new probes for studying human telomeres under mild conditions. Herein, to improve their selectivities to telomeres by targeting longer sequences, we designed and synthesized a fluorescent tandem trimer Py–Im polyamide probe, comprising three hairpins and two connecting regions (hinges). The new motif bound to 18 bp dsDNA in human telomeric repeats (TTAGGG)_n, the longest sequence for specific binding reported for Py–Im polyamides. We compared the binding affinities and the abilities to discriminate mismatch, the UV-visible absorption and fluorescence spectra, and telomere staining in human cells between the tandem trimer and a previously developed tandem hairpin. We found that the tandem trimer Py–Im polyamide probe has higher ability to recognize telomeric repeats and stains telomeres in chemically fixed cells with lower background signal.     

Study on orientation mechanisms of poly(vinylidenefluoride-trifluoroethylene) molecules aligned by atomic force microscopy

We have developed a molecular orientation control technique for polymers utilizing contact-mode atomic force microscopy (AFM). In this paper, we studied the molecular alignment mechanism of this technique by applying it to poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)). The resultant alignment and formed crystal size were strongly dependent on the temperature during the modification. They also depended on the scan line spacing of the modification. These results made the alignment mechanism clear. The obtained molecular alignment was stable against the heat treatment even at the temperatures just below T_m.     

Photopolymerization of β-Allyloxypropionaldehyde

Homo- and copolymerizations of β-allyloxypropionaldehyde (I) have been carried out by photoirradiation at 12–13°C in degassed glass ampules. The number-average molecular weights of the homopolymers of I obtained in a few reaction conditions were determined by means of gel-permeation chromatography. I initiated and/or accelerated the photopolymerizations of such vinyl monomers as methyl methacrylate and vinyl acetate. Photocopolymerizabilities of I with styrene (St) and acrylonitrile (AN) were also investigated, and the copolymerization parameters were obtained as follows: for the St-I system, r₁ = 12, r₂ = 0.01; for the AN-I system, r₁ = 5.2, r₂ = 0.01.     

Radical Polymerizability of 6-Methyl-2-vinyl-3-pyridazinone in Protic Media

Abstract

Radical copolymerizability of 6-methyl-2-vinyl-3-pyridazinone (I) has been reinvestigated in acetic acid and also in the presence of polyacrylic acid (PAA). Copolymerization of styrene with I was carried out in a few solvents. A positive e₂ value was obtained in acetic acid while negative ez values were obtained in benzene and DMF. I was allowed to copolymerize with a few monomers such as styrene, methyl methacrylate, and acrolein in the presence of PAA to give block-type copolymers. All these observations indicate that polymerizability of I is controlled by the hydrogen bonding interaction between the carbonyl group of I and the hydroxyl group of the additive.     

Differences of fluorine in cements determined by photometric methods after distillation and pyrolysis.

Using a spectrophotometric method after distillation separation is a standard test method widely employed for the determination of fluorine (F) in cement. Using a flow injection (FI) method after pyrolysis separation for quantification of fluorine in cement has recently been developed. Differences between the fluorine content values obtained by each method have been noted. This paper documents the differences between fluorine content (distillation F) measured spectrophotometrically after distillation and that (pyrolysis F) determined using the FI method after pyrolysis for fourteen commercial Portland cements and identifies a factor contributing to the differences between distillation F and pyrolysis F values. A highly significant relationship existed between distillation F and pyrolysis F values for fourteen cements (r(2) = 0.998, p < 0.001).