Cationic photopolymerization of 1,3-di(9-carbazolyl)-2-propanol glycidyl ether

An absorbance probe method was used for the investigation of photolysis of cationic photoinitiators. The rates of the photolysis of diphenyliodonium hexafluorophosphate (DPIH), diphenyliodonium tetrafluoroborate (DPIB), di(tert-butylphenyl)iodonium tetrafluoroborate (DTIB), di(tert-butylphenyl)iodonium bromate (DTIBr), triphenylsulfonium hexafluorophosphate (TPS) and cyclopropyldiphenylsulfonium tetrafluoroborate (CPS) were studied in the presence of acid indicator quinaldine red (QR) in acetonitrile. Diphenyliodonium hexafluorophosphate and triphenylsulfonium hexafluorophosphate showed the highest photolysis rate. Photopolymerization of 1,3-di(9-carbazolyl)-2-propanol glycidyl ether (DCPGE) initiated with the iodonium and sulfonium salts in bulk and in solution was studied. It was established that the highest initial rate of polymerization is characteristic of DCPGE photopolymerization initiated with DPIH and TPS in bulk. The oligomers of DCPGE of number average molecular weight ( ) ranging from 710 to 1220 were obtained in these reactions in bulk and those with ranging from 1300 to 1600 were obtained in solution. Correspondence: Ruta Lazauskaite, Juozas V. Grazulevicius, Department of Organic Technology, Kaunas University of Technology, Radvilenu plentas 19, LT-50254 Kaunas, Lithuania.     

Phase equilibria in the PbSe-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript>-Se system and thermodynamic properties of intermediate phases

The Pb-Bi-Se system in the PbSe-Bi₂Se₃-Se-Se composition region was studied by measurement of concentration circuits of the type (−) PbSe(solid) liquid electrolyte, Pb²⁺(Pb-Bi-Se)(solid) (+) in the temperature range 300–430 K and by X-ray powder diffraction. A solid-phase equilibrium diagram was constructed, and the formation was confirmed for the ternary compounds Pb₅Bi₆Se₁₄, Pb₅Bi₁₂Se₂₃, and Pb₅Bi₁₈Se₃₂, which belong to the homologous series [(PbSe)₅] _m · [(Bi₂Se₃)₃] _n . From the emf versus temperature equations, the partial thermodynamic functions [`(DG)]\overline {\Delta G}, [`(DH)]\overline {\Delta H}, [`(DS)]\overline {\Delta S} of PbSe in alloys were calculated. Based on the solid-phase equilibrium diagram from these partial molar quantities using the corresponding data for PbSe and Bi₂Se₃, the standard thermodynamic functions of formation and standard entropies of the above ternary compounds were calculated.     

Mean polarizability of molecules and anisotropy of the Lorentz tensor upon a nematic-smectic a phase transition: Their behavior in a homologous series

Experimental values of the mean polarizability of molecules, [`(g)]\bar \gamma , and components of the Lorentz tensor, L <sub>j</sub> , in the nematic and smectic A phases are obtained for a homologous series of n-alkyl-p-(4-ethoxybenzylideneamino)-α-methylcinnamates. Dependences of the [`(g)]\bar \gamma and L _j values on the mesophase temperature, the orientational order parameter S of molecules, and the number n in the homologous series are revealed. The quadratic dependence of [`(g)]\bar \gamma (S) in the nematic and smectic phases is established that is invariant with respect to the nematic-smectic A transition. Polarizability densities of the molecular core and the alkyl chain are found from the monotone decreasing dependence [`(g)]\bar \gamma (n)/v (where v is volume per one molecule) in the smectic phase. The presence (or absence) of the odd-even alternation of L _j (n) in the nematic (smectic) phase is shown. A monotone decrease in the Lorentz tensor anisotropy L with an increase in n is revealed in the smectic phase, and limiting values L _j (n → ∞) are determined.     

Photolysis-induced micellization of a poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer

A novel micellization induced by photolysis was attained using a poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light scattering demonstrated that the copolymer produced spherical micelles in dichloromethane by the irradiation with a high-pressure mercury lamp in the presence of photoacid generators, such as bis(alkylphenyl)iodonium hexafluorophosphate (BAI), diphenyliodonium hexafluorophosphate (DPI), and triphenylsulfonium triflate (TPS). The irradiation time to promote the micellization increased in the order of BAI < DPI < TPS, depending on the UV absorption intensity of the photoacid generators. The efficiency to promote the micellization was also dependent on the block length of the copolymer. Under an identical PBSt block length, the copolymer with the shorter PSt block length more easily formed micelles. The ¹H NMR analysis confirmed that the PBSt-b-PSt copolymer was converted into poly(4-vinyl phenol)-block-PSt, resulting in micelles by self-assembly.     

Excess Molar Volumes, Excess Viscosities and Ultrasonic Speeds of Sound of Binary Mixtures of 1,2-Dimethoxyethane with Some Aromatic Liquids at 298.15 K

Densities, viscosities and ultrasonic speeds of sound for binary mixtures of 1,2-dimethoxyethane (DME) with benzene, toluene, chlorobenzene, benzyl chloride, benzaldehyde, nitrobenzene, and aniline are reported over the entire composition range at ambient pressure and temperature (i.e., T=298.15 K and p=1.01×10⁵ Pa). These experimental data were utilized to derive the excess molar volumes (V_m^EV_{\mathrm{m}}^{\mathrm{E}}), excess viscosities (η ^E), and various acoustic parameters including the deviation in isentropic compressibility (Δκ _S ), internal pressure (π _I), and excess enthalpy (H ^E). From the excess molar volumes (V_m^EV_{\mathrm{m}}^{\mathrm{E}}), the excess partial molar volumes ([`(V)]<sub>m,1</sub><sup>E</sup>\overline{V}_{\mathrm{m},1}^{\mathrm{E}} and [`(V)]_m,2^E\overline{V}_{\mathrm{m},2}^{\mathrm{E}}) and excess partial molar volumes at infinite dilution ([`(V)]<sub>m,1</sub><sup>0,E</sup>\overline{V}_{\mathrm{m},1}^{0,\mathrm{E}} and [`(V)]_m,2^0,E\overline{V}_{\mathrm{m},2}^{0,\mathrm{E}}) were derived and discussed for each liquid component in the mixtures. The excess/deviation properties were found to be either negative or positive, depending on the molecular interactions and the nature of the liquid mixtures.     

Rheologic studies on chemical cross-linking kinetics for LDPE

Crosslinking reaction of LDPE resin in the presence of dicumyl peroxide(DCP) was studied by isothermal rheological measurements at different temperatures and non-isothermal differential scanning calorimetry(DSC) technique with different heating rates.The kinetic parameters of crosslinking reaction were calculated by both rheological and DSC measurements.The results reveal that with the increase of DCP contents,the apparent activation energy,E_a,ranges from about 140 kj/mol to 170 kj/mol and the order of crosslinking reaction,n,approaches unity.The influence of measurement frequency,ω,on crosslinking reaction was also investigated.It can be found that n does not change with the increase ofω, and E_a decreases slightly with the increase ofω.     

Densities, Specific Heat Capacities, Apparent and Partial Molar Volumes and Heat Capacities of Glycine in?Aqueous Solutions of Formamide, Acetamide, and?N,N-Dimethylacetamide at T=298.15?K and?Ambient Pressure

Apparent molar volumes (V _2,φ ) and heat capacities (C _p2,φ ) of glycine in known concentrations (1.0, 2.0, 4.0, 6.0, and 8.0 mol⋅kg⁻¹) of aqueous formamide (FM), acetamide (AM), and N,N-dimethylacetamide (DMA) solutions at T=298.15 K have been calculated from relative density and specific heat capacity measurements. These measurements were completed using a vibrating-tube flow densimeter and a Picker flow microcalorimeter, respectively. The concentration dependences of the apparent molar data have been used to calculate standard partial molar properties. The latter values have been combined with previously published standard partial molar volumes and heat capacities for glycine in water to calculate volumes and heat capacities associated with the transfer of glycine from water to the investigated aqueous amide solutions, D[`(V)]<sub>2,tr</sub><sup>o</sup>\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} respectively. Calculated values for D[`(V)]<sub>2,tr</sub><sup>o</sup>\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} are positive for all investigated concentrations of aqueous FM and AM solutions. However, values for D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} associated with aqueous DMA solutions are found to be negative. The reported transfer properties increase with increasing co-solute (amide) concentration. This observation is discussed in terms of solute + co-solute interactions. The transfer properties have also been used to estimate interaction coefficients.     

Iodonium‐polyoxometalate and thianthrenium‐polyoxometalate as new one‐component UV photoinitiators for radical and cationic polymerization

Four novel onium salts (onium‐polyoxometalate) have been synthesized and characterized. They contain a diphenyliodonium or a thianthrenium (TH) moiety and a polyoxomolybdate or a polyoxotungstate as new counter anions. Outstandingly, these counter anions are photochemically active and can sensitize the decomposition of the iodonium or TH moiety through an intramolecular electron transfer. The phenyl radicals generated upon UV light irradiation (Xe–Hg lamp) are very efficient to initiate the radical polymerization of acrylates. Cations are also generated for the cationic polymerization of epoxides. Remarkably, these novel iodonium and TH salts are characterized by a higher reactivity compared with that of the diphenyliodonium hexafluorophosphate and the commercial TH salt, respectively. Interpenetrating polymer networks can also be obtained under air through a concomitant cationic/radical photopolymerization of an epoxy/acrylate blend (monomer conversions > 65%). The photochemical mechanisms are studied by steady‐state photolysis, cyclic voltammetry, and electron spin resonance techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 981–989     

The influence of crystal formation on segmental mobility in polymers: hints from a statistical mechanical relaxation model

A statistical mechanical model is used to analyze literature data regarding the restricted segmental dynamics of a number of crystallized polymers, as observed by means of broadband dielectric spectroscopy. A relationship between well defined physical quantities and the width parameter in the Havriliak–Negami representation of symmetric processes is established. It is found that, for materials crystallized from an isotropic amorphous state, the segmental relaxation process is associated to conformational changes within cooperatively rearranging regions of ~1 nm diameter. In case of chain orientation, the dimension of the rearranging regions along the chain direction increases up to 3–5 nm. It is argued that the average size of the rearranging regions may influence the thickness of the amorphous interlamellar layers in the stacks. It is also found in all cases that, at the end of the crystallization process, the average fluctuation component of the chemical potential within the confined amorphous regions, $\overline{\Delta\mu}A statistical mechanical model is used to analyze literature data regarding the restricted segmental dynamics of a number of crystallized polymers, as observed by means of broadband dielectric spectroscopy. A relationship between well defined physical quantities and the width parameter in the Havriliak–Negami representation of symmetric processes is established. It is found that, for materials crystallized from an isotropic amorphous state, the segmental relaxation process is associated to conformational changes within cooperatively rearranging regions of ~1 nm diameter. In case of chain orientation, the dimension of the rearranging regions along the chain direction increases up to 3–5 nm. It is argued that the average size of the rearranging regions may influence the thickness of the amorphous interlamellar layers in the stacks. It is also found in all cases that, at the end of the crystallization process, the average fluctuation component of the chemical potential within the confined amorphous regions, [`(Dm)]\overline{\Delta\mu}, is of the same order of the chemical potential drop Δμ <sub>cryst</sub> associated to crystallization from the undercooled, relaxed melt. Except in one among the cases considered, it is found that [`(Dm)] ? - Dm_cryst\overline{\Delta\mu}\approx - \Delta\mu_{\rm cryst}, which is a hint towards the formalization of a thermodynamic criterion for crystallization arrest.     

Photocationic and radical polymerizations of epoxides and acrylates by novel sulfonium salts

Novel sulfonium salts [methyl‐, 2‐indany‐, or 1‐ethoxycarbonylethyl methyl‐2‐naphthylsulfonium hexafluorophosphate and 2‐indany‐, 1‐ethoxycarbonylethyl‐, 2‐methyl‐2‐phenylpropyl‐, 2‐phenylpropyl‐, 2‐phenylethyl‐, 2‐(4‐methoxyphenyl)‐ethyl‐, or 3‐(4‐methoxyphenyl)‐2‐propyl methylphenylsulfonium hexafluorophosphates] were synthesized by the reaction of dimethylsulfate and the corresponding sulfides followed by anion exchange with KPF₆. These sulfonium salts could polymerize epoxy monomers at lower temperatures than previously reported for benzylsulfonium salt initiators. In particular, sulfonium salts with naphthyl groups showed higher photoactivity than already reported for di(4‐tert‐butylphenyl)iodonium and triphenylsulfonium hexafluorophosphates. These sulfonium salts showed higher activity in photoradical polymerization and photocationic polymerization. The photopolymerization was accelerated by the addition of 4‐methoxy‐1‐naphthol, N‐ethylcarbazole, 2,4‐dimethylthioxanthone, phenothiazine, and 2‐ethyl‐9,10‐dimethoxyanthracene as photosensitizers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3816–3827, 2003     

Photoinitation of cationic polymerization. II. Laser flash photolysis of diphenyliodonium salts

Laser flash photolysis of diphenyliodonium salts produces phenyliodinium radical cation (PhI^+·), which was also generated independently by flash-induced electron transfer from iodobenzene to a phenanthrolinium salt. Apparent second-order rate constants were determined for reaction of the transient (PhI^+·) with nucleophiles, including iodobenzene and cyclohexene oxide. Quantum yields of formation of acid from stationary photolysis of diphenyliodonium hexafluoroarsenate were found to be significantly higher than yields of iodobenzene. These results may be explained by facile reaction of PhI^+· with PhI to yield a new iodonium salt together with a proton. High reactivity of PhI^+· with cyclohexene oxide suggests that the transient may directly initiate cationic polymerization of epoxides.     

Micelle formation induced by photolysis of a poly(<Emphasis Type="Italic">tert</Emphasis>-butoxystyrene)-<Emphasis Type="Italic">block</Emphasis>-polystyrene diblock copolymer

We found the novel photolysis-induced micellization of the poly(tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). PBSt-b-PSt with a molecular weight of Mn(PBSt-b-PSt) = 15,000-b-97,000 showed no self-assembly in dichloromethane and existed as isolated copolymers with a hydrodynamic diameter of 16.6 nm. Dynamic light scattering demonstrated that the copolymer produced micelles with a 63.0 nm hydrodynamic diameter when the copolymer solution was irradiated with a high-pressure mercury lamp at room temperature in the presence of bis(alkylphenyl) iodonium hexafluorophosphate, a photoacid generator. The ¹H NMR analysis revealed that the micellization resulted from the photolysis of the PBSt blocks into insoluble poly(vinyl phenol) blocks based on the fact that the signal intensity of the tert-butyl protons decreased over time during the irradiation. It was found that the micellization rapidly proceeded as the degree of the photolysis reached over 50% and was completed at 90%.     

Synthesis and characterization of amphiphilic and hydrophobic ABA-type tri-block copolymers using telechelic polyurethane as atom transfer radical polymerization macroinitiator

Atom transfer radical polymerization of 2-(dimethylamino) ethylmethacrylate and styrene was carried out using tertiary bromine-terminated telechelic polyurethane as a macroinitiator. The resulting ABA-type amphiphilic, poly (2-(dimethylamino) ethylmethacrylate)-b-polyurethane-b-poly (2-(dimethylamino) ethylmethacrylate) and hydrophobic, polystyrene-b-polyurethane-b-polystyrene tri-block copolymers were characterized by spectral, thermal, and chromatographic techniques. As the conversion increases, [`(M)]<sub>\textn</sub> {\overline M_{_{\text{n}}}} also increases linearly. Theoretical M <sub>n</sub> values of the tri-block copolymers were comparable with the experimental [`(M)]_\textn {\overline M_{_{\text{n}}}} values. These results show that the polymerization of styrene and 2-(dimethylamino) ethylmethacrylate occurred through controlled radical polymerization mechanism. Mole percentage of polystyrene and poly (2-(dimethylamino) ethylmethacrylate) blocks in the tri-block copolymers was calculated using proton nuclear magnetic resonance spectroscopy, and the results were comparable with the gel permeation chromatography results. The glass transition temperatures of polystyrene and poly (2-(dimethylamino) ethylmethacrylate) blocks in the tri-block copolymers appeared at 72 °C and 110 °C, respectively. These results confirm the presence of two phases in the tri-block copolymers.     

Photoinitiated cationic polymerization of monofunctional benzoxazine

The photoinitiated ring‐opening cationic polymerization of a monofunctional benzoxazine, 3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine, with onium salts such as diphenyliodonium hexafluorophosphate and triphenylsulfonium hexafluorophosphate as initiators was examined. The structures of the polymers thus formed were complex and related to the ring‐opening process of the protonated monomer either at the oxygen or nitrogen atoms. The phenolic mechanism also contributed, but its influence decreased with decreasing monomer concentration. Thermal properties of the polymers were also investigated by differential scanning calorimetry and thermogravimetric analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3320–3328, 2003     

Volumetric Properties of Acetonitrile with 1,2-Alkanediols (C2–C6) at 20°C

Dilatometric measurements of excess molar volumes, V^E and excess partial molar volumes, [`(V)] <sub>\texti</sub><sup>\textE</sup>\overline V _{\text{i}}^{\text{E}} have been made for binary mixtures of acetonitrile with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 20°C over the entire composition range. V<sup>E</sup> for acetonitrile + 1,2-ethanediol and 1,2-propanediol mixtures are negative over the entire range of mole fractions and positive values are obtained for all remaining mixtures. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through O—H...N=C hydrogen bonding. From the experimental results, V<sup>E</sup> were calculated and correlated by Redlich–Kister type function in terms of mole fractions. The excess partial molar volumes were extrapolated to zero concentration to obtain the limiting values at infinite dilution, [`(V)] _\texti^\textE,o\overline V _{\text{i}}^{{\text{E,o}}} .     

Diphenylphenacyl sulfonium salt as dual photoinitiator for free radical and cationic polymerizations

Diphenylphenacylsulfonium tetrafluoroborate (DPPS⁺BF^4–) salt possessing both phenacyl and sulfonium structural units was synthesized and characterized. DPPS⁺BF^4– absorbs light at relatively higher wavelengths. The direct and sensitized initiation activity of the salt in both cationic and free radical photopolymerizations was investigated and compared with that of its analogue triphenylsulfonium tetrafluoroborate (TPS⁺BF^4–). Differential scanning photocalorimetry and conventional gravimetric studies revealed that DPPS⁺BF^4– showed higher efficiency for direct and sensitized photopolymerizations of most of the monomers investigated. Although, principally both homolytic and/or heterolytic cleavage is possible, theoretical studies suggested that homolytic pathway is more favored for the generation of reactive initiating species. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 451–457     

Verbindungen des Germaniums und Zinns. 3. Sterisch überladene Alkylarylstannane durch Übertragung und Isomerisierung von 2,4,6-Tri-tert-butylphenylgruppen

Compounds of Germanium and Tin. 3. Sterically Congested Alkylarylstannanes by Transfer and Isomerization of 2,4,6-Tri-tert-butylphenyl Groups Reaction of SnBr₄ and SnI₄ with 2,4,6-tri-tert-butylphenyllithium (ArLi) by rearrangement of two Ar-groups gives the stannanes ArR₂SnBr ( 3 ) and ArR₂SnI ( 4 ), R = 2-methyl-2(3,5-di-tert-butylphenyl)propyl, which by a further transalkylation reaction with methyl lithium yield ArR₂SnCH₃ ( 5 ). However, treatment of 3 and 4 with tert-butyl lithium exclusively leads to ArR₂SnH ( 6 ) which surprisingly is also obtained by reaction of ArRSnCl₂ with tert-butyl lithium, presumably by an intermolecular R-group transfer. The structures of 5 and 6 were confirmed by X-ray crystallography.     

Synthesis of uniform polyurethane particles by step growth polymerization in a dispersed medium

Polyurethane microspheres were prepared by polyaddition of ethylene glycol (EG) and tolylene-2,4-diisocyanate (TDI) at 60 °C in cyclohexane as the organic dispersion medium, in the presence of dibutyl tin dilaurate (DBTDL) as catalyst and poly(styrene)-b-poly(ethylene oxide) block copolymers or P-hydroxypolystyrenes as the steric stabilizers. Different parameters such as the manner of addition of the reactants, the concentration, and length of the stabilizer were varied to tune the polyurethane particle size. When P-OH polystyrenes of low molar mass ([`(M)]_n\bar M_n =2000-3000 g mol^-1) were used as the reactive stabilizers of dispersion, polyurethane particles in a tunable size range of 0.2-5 µm with a narrow size distribution (span = 0.7) could be prepared.     

Enhancing the solubility for hypervalent ortho-sulfonyl iodine compounds

The synthesis and characterization of new hypervalent iodine reagents ArINTs (2a), ArIO (3a), and ArIO₂ (4a) (Ar=2-tert-butylsulfonyl-5-tert-butylphenyl) are described. These reagents are compared to previously reported analogous set of reagents Ar=2-tert-butylsulfonylphenyl and found to have significantly enhanced solubility and similar chemical reactivity. The X-ray crystal structures of 4a and of ArI (1a) (Ar=2-tert-butylsulfonyl-5-tert-butylphenyl) are discussed and compared. These reagents find use in atom and group transfer reactions.     

Preparative syntheses of bis(4-tert-butylphenyl)aminoxyl

Bis(4-tert-butylphenyl)aminoxyl was obtained in 80 and 95% yield by oxidation of the corresponding amine and hydroxylamine with H₂O₂/WO ₄ ^2? in methanol at 65°C. The oxidation of bis(4-tert-butylphenyl)hydroxylamine to bis(4-tert-butylphenyl)aminoxyl was catalyzed by Cu⁺ and Ag⁺ ions which also catalyzed disproportionation of the former to bis(4-tert-butylphenyl)amine and bis(4-tert-butylphenyl)aminoxyl. Mechanisms of the catalytic oxidation of the amine and hydroxylamine and disproportionation of the latter were proposed.