Four-center type photopolymerization in the solid state. VII. Photochemical reaction of m-phenylene diacrylic acid dimethyl ester

The photochemical reaction of m-phenylene diacrylic acid dimethyl ester (m-PDA Me) crystals and solutions has been studied to clarify the effects of the molecular shape on four-center type photopolymerization of diolefins. On irradiation, m-PDA Me crystals were converted into amorphous oligomers having more than two kinds of cyclobutane rings with respect to steric configuration. The characteristic oligomer formation is explained by considering a two-step mechanism: topochemical dimer formation in an ordered crystal lattice and subsequent random cycloaddition in a disordered crystal lattice. In m-PDA Me solution, reversible cyclobutane ring formation and cis–trans isomerization take place, depending on the concentration of m-PDA Me in solution and the wavelength of the irradiating light. The multiplicity of reactivity in various states has been established.     

Four-center type photopolymerization in the solid state. II. Polymerization mechanism of 2,5-distyrylpyrazine

The polymerization mechanism of trans,trans-2,5-distyrylpyrazine (DSP) has been investigated and some crystal changes along with the polymerization process have been observed through polarizing microscope and x-ray diffraction pattern. Information has been obtained on the active species, polymerization reaction type, and other factors such as light intensity, reaction temperature, or crystalline state. The polymerization of DSP occurs only in the solid state by photoirradiation. Reduced viscosity increases gradually with the increase of conversion and increases sharply above 80% conversion. Polymerization rate increases with the increase of light intensity and temperature. On the other hand, reduced viscosity decreases with the increase of temperature but does not depend on light intensity within the range investigated. The polymer obtained at low conversion as well as at high conversion has high crystallinity, and the direction of polymer axes is simply related to that of monomer crystal. It was concluded that the four-center type polymerization of DSP proceeds topochemically by a photochemically induced stepwise mechanism.     

Four-center type photopolymerization in the solid state. I. Polymerization of 2,5-distyrylpyrazine and related compounds

Crystalline 2,5-distyrylpyrazine (DSP) was found to polymerize into a linear high polymer with extremely high crystallinity by the action of sunlight or ultraviolet light. Based on this discovery, photopolymerizability of the related diolefins having the general formula, trans,trans-Ar′? CH?CH? Ar? CH?CH? Ar′ was surveyed. As a result, 1,4-bis[β-pyridyl-(2)-vinyl]benzene (P2VB) was found to polymerize in the same way as DSP. The polymers as polymerized, showed a high melting temperature (>330°C) and were soluble only in strong acids. The structure of the polymers was investigated by means of several customary methods involving infrared and NMR spectrum studies. It was concluded that both poly-DSP and poly-P2VB consist of a linear structure having a recurring cyclobutane ring in the main chain. General properties of this novel polymer were studied.     

Four-center type photopolymerization in the solid state. IV. Polymerization of α,α′-dicyano-p-benzenediacrylic acid its derivatives

The solid-state photopolymerization of α,α′-dicyano-p-benzene diacrylic acid (p-CBA) series has been studied. p-CBA, its esters, amide, and a few other cyano derivatives were prepared and new polymers were obtained from p-CBA alkyl esters on irradiation of ultraviolet or visible light. Though the polymerization behavior differs with each monomer, polymerization proceeds in essentially the same manner as in the 2,5-distyrylpyrazine (DSP) and p-benzenediacrylic acid (BDA) series: the reaction proceeds topochemically forming polymer with a cyclobutane ring in the main chain. Properties of high polymer are typical of cyclobutane-containing polymer. That is, they are highly crystalline with high melting temperature and a limited solubility. The study on this series of compounds, as well as the DSP and p-BDA series, supports the generalization that solid-state dimerization can be extended to solid-state photopolymerization of compound having two dimerizable units in a molecule.     

Four-center type photopolymerization in the crystalline state. VI. Kinetic and structural study of the polymerization of p-phenylenediacrylic acid diethyl ester

The effect of temperature on the four-center type photopolymerization has been investigated for p-phenylenediacrylic acid diethyl ester over a wide temperature range including crystal transition point (56°C) and melting point (96°C) of monomer. With the elevation of temperature between ?50 and 15°C, the polymerization rate in the initial stage increased and the degree of polymerization decreased monotonously, while the rate in the later stage decreased above ?25°C. With irradiation at above 25°C, the monomer crystals became sticky, and the polymerization was suppressed at the stage of oligomerization with low conversion. This tendency was enhanced above the crystal transition point, giving mainly dimer in low yield. Above the melting point, only radical polymerization occurred with the aid of oxygen. The steric configuration of the products in the crystalline state was 1,3-trans with respect to the cyclobutane ring. Peaks in NMR spectra of all products were assigned to the protons involved in four compounds up to tetramer. Various results obtained have been interpreted in terms of the change, as a function of temperature, from a topochemical polymerization which proceeds under a control of the monomer lattice to a photoinitiated vinyl-type polymerization in the disordered state. It is concluded that a rigid crystal lattice is indispensable for the four-center type photopolymerization to proceed smoothly.     

Four-center type photopolymerization in the crystalline state. V. X-ray crystallographic study of the polymerization of 2,5-distyrylpyrazine

Changes in crystal structure during polymerization and oligomerization of 2,5-distyrylpyrazine have been investigated by x-ray crystallography. The polymer and the oligomer as obtained are three-dimensionally oriented, and the directions of the three axes of the resultant crystals coincide with those of the original crystal. The space group of the products also agrees with that of the monomer. It is concluded that the polymer and the oligomer crystals approximately duplicate the molecular arrangement in the monomer crystal. The polymerization mechanism is discussed on the basis of the crystal structures.     

Four-center photopolymerization in the crystalline state. VIII. X-ray crystallographic study of the polymerization of some diolefinic compounds

The four-center photopolymerization of five diolefinic compounds has been investigated by x-ray crystal analysis. A common packing feature is found for the photopolymerizable crystals and all polymers are three-dimensionally oriented. Topotaxies observed are classified according to the coincidence of space group and the three crystal axes, between monomer and polymer. The polymerization mechanism is discussed on the basis of the topotaxies and it is concluded that the polymerization is lattice controlled over the whole reaction process.     

Polymerization of N-carboxy-amino acid anhydrides in the solid state. I. Polymerizability of the various α-amino acid NCAs in the solid state

The solid-state polymerization of various α-amino acid NCAs was investigated and the results were compared with those obtained by heterogeneous polymerization in acetonitrile. Essential differences were found in the polymerizability of the NCAs in these two systems. In the solid state, L-leucine NCA was the most reactive among the NCAs examined, and its reactivity was even higher than in the precipitation polymerization of acetonitrile solutions. On the other hand, glycine NCA was the most inert among the NCAs examined in the solid state. The difference between the reactivities of glycine NCA and L-alanine NCA was interpreted in terms of their crystal structures. Several kinetic features of the solid-state polymerization were studied on γ-benzyl-L -glutamate NCA.     

The structures of bis(3-aminophenyl)phosphinic acid and its derivatives in the solid state

Russian Chemical Bulletin - According to IR spectroscopy data, solid bis(3-aminophenyl)phosphinic acid has a zwitterionic structure.     

Molecular mechanics of photopolymerization of 2,5-distyrylpyrazine in solid state

The molecular mechanics of photopolymerization of 2,5-distyrylpyrazine in the solid-state α form is investigated by a combination of Raman and electronic spectroscopic techniques. A stepwise photoreaction is used to stabilize an intermediate oligomer structure. For this purpose, the 476.5-nm argon-ion laser line is used to convert the monomer to the oligomer. The Raman phonon spectra reveal a homogeneous mechanism, with considerable lattice rearrangement, for the oligomerization process, which is also found to produce lattice strain. Further photoreaction of the oligomer is carried out with light of wavelength ≤400 nm from a 200-W mercuryxenon lamp as well as with the 355- and 417-nm laser lines from a Nd: Yag laser system. The Raman phonon spectra, monitored during the conversion of the oligomer to the polymer, show that initially the process starts homogeneously, with considerable lattice rearrangment. Then it turns heterogeneous, with a phase separation accompanied by a gradual ordering of the polymer product lattice. The electronic absorption spectra of the monomer are characterized and related to the stepwise photo process discussed above. Although the emission spectra show a monotonic change during the photoreaction, energy transfer from the oligomer to the monomer and from the polymer to the oligomer obscures and quantitative characterization by emission spectroscopy.     

Solid state polymerization of butadienes. Polymerization of long chain derivatives of sorbic and muconic acid

The polymerization of long chain derivatives of sorbic and muconic acid was studied in the solid state. Crystals of sorbic acid n-octadecylester (1), sorbic acid n-octadecylamide (2), and 6-n-octadecanoylamino sorbic acid (3) were found to rapidly polymerize upon UV- or-irradiation. A 1,4-trans-polymer was obtained in a high yield. Crystals of muconic acid di-n-octadecylester (4) and muconic acid di-n-octadecylamide (5) were completely photoinactive.Polymerization of3 was also investigated in monomolecular layers at the air-water interface and in Langmuir-blodgett type multilayers. The polymer formed upon UV- irradiation of mono- and multilayers was identified by infrared spectroscopy as the 1,4-trans-adduct.     

Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. I. Polymerization conditions and polymer characterization

The solid-state 1,3,5-trithiane polymerization initiated by UV-irradiation was studied at various irradiation times and various polymerization temperatures. The conversion of monomer to polymer reaches limiting values (at longest) in about 30 min of reaction. The apparent activation energy of this process is somewhat higher than in the chemically initiated polymerization. Generated by UV, active centers, which initiate the polymerization, are stable. On the basis of X-ray diffraction studies it was found that the prepared polythiomethylene has a hexagonal structure and high degree of crystallinity. In the polymer investigated, a new additional crystal phase is formed, which is not stable.     

ESR analysis of the initial reaction products in the solid state photopolymerization of diacetylenes

In order to investigate the mechanism of the solid state photopolymerization of single crystals of the bis(p-toluene sulphonate) ester of 2,4-hexadiyne-1,6 diol (TSHD) the low temperature UV-photoproducts are analyzed by ESR-spectroscopy. In this paper we report the fine structure, hyperfine structure and temperature dependence of a series of thermally activated triplet diradicals. The structure of these diradical dimer and trimer initiators of the UV-photopolymerization process is deduced from the analysis of the ESR data.     

Effects of rotational symmetry order on the solid state dynamics of phenylene and diamantane rotators

The rotational dynamics of phenylene and diamantane rotators in crystals of 1,9-bis(4-[3,3,3-triphenylpropynyl]phenyl)diamantane were analyzed independently within the same crystal structure. The dynamics of phenylene rotation were established by dynamic line shape analysis using 13C CPMAS NMR. The phenylene signals were selectively highlighted by deuteration of the aromatic trityls and the use of short contact times for cross polarization. The dynamics of the diamantane group were established by 1H spin-lattice relaxation under conditions where dipolar relaxation was shown to be the dominant mechanism between 250 and 425 K. A factor of 20 000 between the rates of rotation of the faster diamantane and the slower phenylene at 300 K supports expectations that higher symmetry rotors should have significantly faster dynamics.     

13C-NMR study of cellulose derivatives in the solid state

The application of NMR for natural organic compounds has been carried out from the early history of NMR. But they reported on the liquid state NMR and the samples were limited to the materials which dissolved in proper solvents. It has been possible to measure the samples in the solid state in 1970s and is widely used as a familiar analytical method in 1980s. Whereas some of the data is inadequate, concerning cellulose derivatives, in particular, only nitrate and acetate were reported by Patterson¹ and Doyle,² respectively. In this paper, the ¹³C CP/MAS solid state NMR spectra of several cellulose derivatives are shown and the relationship between the structure and spectrum is discussed.     

Reactive crystals. IV. Crystalline state photopolymerization of 5,5′-1,4-phenylene-bis(2-cyano-2,4-pentadienoic acid) derivatives

5,5′-1,4-Phenylene-bis(2-cyano-2,4-pentadienoic acid) derivatives were prepared. Many of this series of compounds were found to be polymerizable in the crystalline state by irradiation with light of wavelength λ > 340 nm. The polymers obtained contain a benzene and a cyclobutane ring in the main chain and have a cyanoacrylate as the side chain. They are crystalline and some of them are soluble in organic solvents. Photopolymerization was found to follow a stepwise mechanism. The polymerization process is separable into an oligomerization and a subsequent polymerization by controlling the wavelength of the irradiating light; an oligomer was obtained by an irradiating light; an oligomer was obtained by an irradiating light of wavelength λ > 430 nm.     

Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. II. Investigation of the initiation process

The influence of the irradiation and polymerization atmosphere on polymer yield was observed. It was shown that in the initiation process oxygen presence is necessary. ESR studies of UV-and γ-irradiated 1,3,5-trithiane were done. The influence of the irradiation atmosphere on generated radicals and the influence of UV-action on radicals formed by γ-irradiation was also investigated. The possible initiation mechanism of cationic polymerization of 1,3,5-trithiane is discussed. A comparison of the 1,3,5-trithiane is polymerizations initiated chemically and by UV- or γ-irradiation is also given.