Photocrosslinking of poly(2,3-epithiopropyl methacrylate) film with 254 nm irradiation

Poly(2,3-epithiopropyl methacrylate) (PETMA) has an absorption maximum at 258 nm (ε_max = 50) in dioxane which is due to episulfide groups. When irradiated at 254 nm under atmospheric pressure its film became insoluble. When kept at 70°C for several minutes a PETMA film became partially insoluble; however, the contribution of this thermal reaction to the photocrosslinking at room temperature was negligible. For photoreaction at 254 nm under nitrogen a low probability of main-chain scission was ascertained by the use of the Charlesby-Pinner equation. The IR spectrum of irradiated PETMA showed a decrease in episulfide groups and the formation of mercapto groups, which suggested that the photocrosslinking of PETMA results from free radicals formed by the cleavage of C? S bonds. Free radicals in the irradiated PETMA were detected by ESR spectroscopy and the assignment is discussed. In this photocrosslinking process oxygen was a retarder at the early stage but an accelerator at the later stage.     

Some transformations of N-(2,3-epoxypropyl)-1,8-naphthosultam

A method of synthesis has been developed for N-(2,3-epoxypropyl)-1,8-naphthosultam and some transformations of this compound were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 236–242, February, 2000.     

Synthesis and thermal reactions of N-(2,3-epoxypropyl)diphenylamine

The synthesis of N-(2,3-epoxypropyl)diphenylamine is reported. It was found that thermal opening of the oxirane ring of N-(2,3-epoxypropyl)diphenylamine occurred both at the secondary and the tertiary carbon atoms but the basic reaction product is 3-hydroxy-1-phenyl-1,2,3,4-tetrahydroquinoline. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 852–855, June, 2007.     

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with poly(butadiene-block-methyl methacrylate)

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 85–93, 1998     

Preparation of poly(hydroxyethyl methacrylate) and poly(hydroxypropyl methacrylate) latices

Hydroxyethyl methacrylate and hydroxypropyl methacrylate (both having extremely high solubilities in water) were polymerized in aqueous medium to obtain the respective polymer latices with a solid content as high as 10 wt.-%. The initial state of the polymerization is in solution rather than in dispersion, and the polymer product is sparingly soluble in the aqueous phase. The polymerization was carefully controlled to avoid forming hydrogel by using an oil soluble initiator and a mixture of sodium dodecyl sulfate and poly(vinyl alcohol). Solubilities of both monomers and polymers in water were also investigated.     

The effects of several sulfonates on thermal and fire retardant properties of poly(methyl methacrylate) and polystyrene

Three different sulfonates (sodium diphenylamine‐4‐sulfonate [SDPAS], 3‐(1‐pyridino)‐1‐propane sulfonate [PPS], and ammonium sulfamate) have been melt blended with polystyrene (PS) or poly(methyl methacrylate) (PMMA) and with clay to make composites. All have been examined by X‐ray diffraction to determine the morphology, by thermogravimetry to determine thermal stabilities, and by cone calorimetry to evaluate fire retardancy. All three sulfonates enhance the thermal stability of the PMMA composites, and SDPAS achieves the greatest improvement. SDPAS also seems to aid in the dispersion of the clay in the polymer. Combination of sulfonates (5 or 10 wt% SDPAS, or 5 wt% PPS) with an organically modified clay exhibit enhanced fire retardancy. The three sulfonates did not enhance the thermal stability of the PS composites; however, there is a reduction in the peak heat release rate. The presence of ammonium sulfamate in PS brings about a 52% reduction in the peak heat release rate. The combination of sulfonates (5 or 10 wt% PPS, or 10 wt% SDPAS) with an organically modified clay provides some fire retardancy to the PS composites. Copyright © 2013 John Wiley & Sons, Ltd.     

Photocrosslinking of poly(2,3-epithiopropyl methacrylate) by the oxidation of pendant episulfide groups

In the photocrosslinking of poly(2,3-epithiopropyl methacrylate) (PETMA) films the effect of the pendant episulfide group's oxidation on the crosslinking of PETMA was investigated. Thermal crosslinking of PETMA is promoted by peroxides such as benzoyl peroxide and hydrogen peroxide. IR spectrum of the crosslinked PETMA showed that the reaction proceeded through the oxidation of episulfide groups by the peroxides. The anthracene (An) sensitized photocrosslinking of PETMA films also proceeded via the oxidation of episulfide groups by singlet oxygen. It was found that residual tetrahydrofuran (THF) in the films remarkably increased the rate of the photocrosslinking and/or reduced the induction period. From the further investigation concerning casting solvents it was found that residual CS₂, CCl₄, and CHCl₃ in films increased the rate of the photocrosslinking and/or reduced the induction period of the photocrosslinking. The disappearance rate of An in the films was also increased by the presence of residual CS₂, CCl₄, and CHCl₃, differring from the result of THF. These results were explained by a difference in lifetime of singlet oxygen in the films. From the results were explained by a difference in lifetime of singlet oxygen in the films. From the results concerning the effects of hydroperoxides such as THF hydroperoxide and t-butyl hydroperoxide on the photocrosslinking of PETMA films the acceleration effect of the residual THF was deduced to be due to the promotion of singlet oxygen-oxidation of sulfide groups by protic compounds such as THF hydroperoxide and H₂O in the THF.     

Relationships between ringed spherulitic morphology and miscibility in blends of poly(ɛ-caprolactone) with poly(benzyl methacrylate) versus poly(phenyl methacrylate)

 Ringed spherulites are an interesting phenomenon that is observed only in very few miscible systems. For the first time, the relationship between the state of chain intermixing and the ring-band pattern was demonstrated. Two previously demonstrated miscible blend systems, poly(ɛ-caprolactone) (PCL) with poly(benzyl methacrylate) (PBzMA) and PCL with poly(phenyl methacrylate) (PPhMA), were studied in order to understand the mechanism of ring-band formation in the spherulites and the relationships between the ring-band pattern and the state of miscibility. In both miscible PCL/PBzMA and PCL/PPhMA systems, extinction rings were observed within the PCL spherulites. In the PCL/PBzMA blend, the extinction rings are not as distinct (owing to distortion) as those in the PCL/PPhMA blend system. Analysis was performed and discussions were made to reveal relationships between miscibility, interaction strength, and the pattern of the ring bands in the PCL spherulites in polymeric mixtures. Received: 5 January 2000/Accepted: 14 March 2000     

Photodegradation of poly(methyl methacrylate)

The vacuum photodegradation at 30°C. of poly(methyl methacrylate) and copolymers with acrylaldehyde, methacrylaldehyde, and methyl acrylate has been studied. The polymers were examined in the form of expanded films as produced by a freeze-drying technique. At least one molecule of carbon monoxide is evolved for each chain scission. It is concluded that chain scission in poly(methyl methacrylate) is primarily the result of photoinduced aldehyde groups.     

Dielectric study of low-temperature relaxations in poly(isobutyl methacrylate), poly(n-butyl methacrylate), poly(isopropyl methacrylate), and poly(4-methylpentene-1)

Isochronal measurements of dielectric constant and loss are made for poly(isobutyl methacrylate) (PiBMA), poly(n-butyl methacrylate) (PnBMA), poly(isopropyl methacrylate) (PiBMA), and poly(4-methylpentene-1) (P4MP1) at temperatures ranging from 4°K to 250°K. Loss peaks are found around 120°K (10–100 Hz) for PiBMA, PnBMA, and P4MP1. By comparing the activation energy with the calculated potential barrier for the internal rotation of alkyl group in the side chain, the motion responsible for the 120°K peak is concluded to be essentially the rotation of the isopropyl group as a whole for PiBMA and P4MP1 but, for PnBMA, the rotation of n-propyl group accompanied by the rotation of the end ethyl group. Multiple paths of internal rotation are involved with the 120°K peaks of PiBMA and, in particular, PnBMA, which explain differences between PiBMA and PnBMA in the broadness and the temperature location of the 120°K peak. The 120°K peak is in general assigned to a side chain including a sequence? O? C? C? C or ? C? C? C? C. PiPMA without this sequence in the side chain does not show the 120°K peak, but it exhibits the 50°K peak (1 kHz) like poly(ethyl methacrylate). The 50°K peak is assigned to the rotation of ethyl or isopropyl group attached to COO group. Poly-L-valine in which the isopropyl group is directly attached to carbon does not have the 50°K peak. An additional loss peak at 20°K (1 kHz) for P4MP1 is also discussed on the basis of the calculated potential.     

Miscibility of bisphenol-A polycarbonate with poly(methyl methacrylate)

The miscibility of bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) has been reexamined using differential scanning calorimetry (DSC) and optical indications for phase separation on heating, i.e., lower critical solution temperature (LCST) behavior. Various methods have been used to prepare the blends including methylene chloride (CH₂Cl₂) and tetrahydrofuran (THF) solution casting, melt mixing, and precipitation of PC and PMMA simultaneously from THF solution by using the nonsolvents methanol and heptane. It is shown that the resulting phase behavior for PC/PMMA blends is strongly affected by the blend preparation method. However, these blends are miscible over the whole blend composition range (unambiguous single composition-dependent T_g's and LCST behavior) when prepared by precipitation from solution using heptane as the nonsolvent. To the contrary, solution-cast and melt-mixed PC/PMMA blends were all phase separated, which may be attributed to the “solvent” effect and LCST behavior, respectively, not discovered in previous reports. Methanol precipitation does not lead to fully mixed blends, which demonstrates the importance of the choice of nonsolvent when using the precipitation method.     

Blends of glycidyl methacrylate/methyl methacrylate copolymers with poly(vinylidene fluoride)

Blends of glycidyl methacrylate (GMA)/methyl methacrylate (MMA) copolymers with poly (vinylidene fluoride) (PVDF) were found to be miscible when the GMA content of the copolymer is 35.7 wt % or less. The miscible blends did not phase separate upon heating prior to thermal decomposition. The melting point depression method, based on both the Flory-Huggins theory and the equation of state theory of Sanchez-Lacombe, was used to evaluate interaction parameters for each pair. The magnitude of these parameters appears to be much larger than interaction energies evaluated by other methods. Possible reasons for this are discussed. © 1995 John Wiley & Sons, Inc.