Styrene Moieties Research Articles

Intramolecular site selectivity in cation radical Diels-Alder cycloadditions of difunctional and trifunctional dienophiles

The cation radical Diels–Alder reactions of several difunctional and trifunctional dienophiles with 1,3-cyclopentadiene, catalyzed by tris(4-bromophenyl)aminium hexachloroantimonate, were determined. When both of the reactive sites are of the 4-methoxystyrene type, reaction occurs smoothly at both styrene moieties to give the bis-adducts. However, when one reactive moiety is of the styrene type and one is of the enol ether type, reaction occurs exclusively at the styrene moiety to give a mono-adduct, even in the presence of a large excess of cyclopentadiene. When three potentially reactive moieties are included, two of them being of the styrene type and one of the 1,2-diaryloxyethene type, the reaction is again specific for the styrene moieties, giving only the bis-adduct. The high site selectivity observed in these reactions is especially noteworthy in view of the observation that monofunctional molecules containing all three of these moieties are found to be reactive toward Diels–Alder adduct formation under the same reaction conditions and that these adducts are relatively stable under the reaction conditions. Copyright ­© 2000 John Wiley & Sons, Ltd.

Amphiphilic block copolymers of controlled dimensions with hydrophilic glycosidic vinyl ether moieties

New amphiphilic diblock copolymers of controlled dimensions constituted of styrene and hydrophilic glycosidic vinyl ether moieties were prepared and their emulsifying properties examined. The hydrophobic block was obtained by living anionic polymerization of styrene, followed by a quantitative functional termination with chloroacetal derivatives. The polystyrene chain ends were then derivatized, by addition of trimethylsilyl iodide, into α-iodo ether macro-initiators. The latter were used to initiate the “living” cationic polymerization of protected glycosidic vinyl ethers, in the presence of weak Lewis acids (typically ZnCl2). The amphiphilic copolymers were obtained by deprotection, in acidic medium, of the hydroxy functions of the sugar of the moieties. The solubility characteristics of these copolymers are discussed with respect to the dimensions of the copolymers and to the hydrophilic/hydrophobic balance between the two blocks.

Amphiphilic block copolymers of controlled dimensions with hydrophilic glycosidic vinyl ether moieties

New amphiphilic diblock copolymers of controlled dimensions constituted of styrene and hydrophilic glycosidic vinyl ether moieties were prepared and their emulsifying properties examined. The hydrophobic block was obtained by living anionic polymerization of styrene, followed by a quantitative functional termination with chloroacetal derivatives. The polystyrene chain ends were then derivatized, by addition of trimethylsilyl iodide, into α-iodo ether macro-initiators. The latter were used to initiate the “living” cationic polymerization of protected glycosidic vinyl ethers, in the presence of weak Lewis acids (typically ZnCl2). The amphiphilic copolymers were obtained by deprotection, in acidic medium, of the hydroxy functions of the sugar of the moieties. The solubility characteristics of these copolymers are discussed with respect to the dimensions of the copolymers and to the hydrophilic/hydrophobic balance between the two blocks.

Effects of oligooxyethylene linkage on intramolecular [2 + 2] photocycloaddition of styrene derivatives

There are two possible explanations for the high yields in the intramolecular [2 + 2] photocycloaddition of compounds 3a–d in which two styrene moieties are bridged by an oligooxyethylene linkage: one is the electronic effects of phenoxy oxygen atoms at the para-position of the vinyl group and the other is the steric effects due to the flexibility of oligooxyethylene linkages. In order to clarify the contributions of the two effects, a study was made of the photoreaction of similar compounds in which oxygen atoms are present only at the ends of the chain, and therefore only the electronic effects are involved. In these compounds, the quantum yields of the photocycloaddition were found to be low. Hence the high yields in the photocycloaddition of 3a–d are concluded to be ascribable to the flexibility of oligooxyethylene linkages. © 1998 John Wiley & Sons, Ltd.

Investigations on Surface-Modified Bulk Polymers. 1. Copolymers of Styrene with a Styrene Moiety Containing a Sugar Monomer

Copolymers containing vinyl sugar units were synthesized by copolymerizing 2,3;4,5-di-O-isopropylidene-1-(4-vinylphenyl)-d-gluco(d-manno)pentitol (1) with styrene. Films and plates of the copolymers and blends were prepared by casting solutions on glass plates or by hot-pressing. Isopropylidene groups, the hydrophobic protecting groups of the sugars (1), were hydrolyzed only in the sample surface layers by treating the films and plates with aqueous acid. The surfaces showed hydrophilic properties afterward and were studied by water contact angle measurement. The accumulation and reorientation of the hydrophilic sugar segments at the surface was demonstrated by a decrease of the receding contact angle and found to depend on the copolymer composition and on sample preparation. The surface compositions of the solution-cast copolymer films were investigated by means of X-ray photoelectron spectroscopy (XPS). The results clearly showed that the isopropylidene groups at the surfaces were removed and the percent...

An IGC Study of Interactions in SAN/SMA Blends

Abstract Inverse gas chromatography has generated surface energy and acid-base interaction data for copolymers of styrene/acrylonitrile (SAN) and styrene maleic anhydride, (SMA) at mole per-cent compositions of SAN-26, SMA-26, and SMA-18. Also measured were polymer pair interaction data for 1:1 weight ratio blends of the copolymers. Explicit values of the X interaction parameter over wide temperature ranges also were obtained from these experiments. SAN was shown to be amphoteric, while SMA polymer surfaces interact as bases. The surface and bulk compositions differ both in single copolymers and polymer blends, with an excess of styrene moieties at surfaces and interfaces resulting from thermodynamic drives to minimize the relevant energies. Miscibility-immiscibility relationships in polymer blends are strongly temperature-dependent. Blends were shown to be miscible below glass transition temperatures, and again at temperatures above about 190°C, with immiscible conditions between these temperature ranges.

Energy migration and transfer in styrene-containing polymers with inhibited excimer formation

Steady-state and time-resolved fluorescence spectroscopic techniques have been used to examine energy transfer and the migration of photoexcitation energy in styrene-containing polymer systems in which excimer formation is inhibited. In particular, copolymers of styrene and p-tert-butyl styrene with acenaphthylene (ACE) acceptor chromophores have been studied. Energy transfer efficiencies between styrene moieties and ACE chromophores incorporated as in-chain traps have been determined and are higher than predicted for a single-step Förster dipole–dipole energy transfer process. The results are discussed with reference to the possible mechanisms for excitation energy transport in these polymers. Keywords: polystyrene fluorescence, energy migration, energy transfer, excimer.

Major groove (R)-alpha-(N6-adenyl)styrene oxide adducts in an oligodeoxynucleotide containing the human N-ras codon 61 sequence: conformations of the R(61,2) and R(61,3) sequence isomers from 1H NMR.

Conformations of (R)-alpha-(N6-adenyl)styrene oxide adducts at positions X6 in d(CGGACXAGAAG).d(CTTCTTGTCCG) and X7 in d(CGGACAXGAAG).d(CTTCTTGTCCG), incorporating codons 60, 61 (underlined), and 62 of the human n-ras protooncogene, were refined from 1H NMR data. These were the R(61,2) and R(61,3) adducts. Chemical shift perturbations were in the 5'-direction from the sites of adduction; large changes were observed for C5 H5 and H6 in the R(61,2) adduct. The styrene moieties were only partially defined by NOE data. Spectral overlap, particularly for the R(61,2) adduct, prevented complete assignments of the aromatic resonances; likewise, there were insufficient data to orient the CH2OH moieties. Ring flips were slow on the NMR time scale. For the R(61,2) adduct 260 restraints were obtained from NOE data at three mixing times using relaxation matrix analysis; for the R(61,3) adduct 230 restraints were obtained. Structures emergent from molecular dynamics/simulated annealing for the R(61,2) adduct converged to average and maximum pairwise rms differences of 1.3 and 1.7 A, respectively, while those for the R(61,3) adduct converged to average and maximum pairwise rms differences of 1.2 and 1.6 A. Sixth root residual indices of 7.5 and 6.8 x 10(-2) were measured between the refined structures and NOE intensities using relaxation matrix calculations for the R(61,2) and R(61,3) adducts, respectively. The styrene rings were in the 5'-direction from the lesion sites in the major groove. The preferred orientation calculated for the R(61,2) adduct placed the styrene ring edgewise and approximately orthogonal to C5, while that calculated for the R(61,3) duplex had the styrene ring approximately orthogonal to the major groove edges of base pairs A6.T17 and R-SOA7.T16.

Intramolecular photoreactions of cyclopentenones and styrenes fixed in a rigid molecule

8- and 9-phenyltricyclo[5.2.1.0 2,6]deca-4,8-dien-3-ones were prepared and their photochemical behavior was examined. Although each of the compounds gave an intramolecular [2+2] cycloaddition product upon direct irradiation, it was found that details of the respective reaction pathways strikingly differ from one another according to orientation of the styrene and enone moieties.

Photopolymers for non‐linear optics: Design and synthesis of a polymer containing styrene‐terminated tolane chromophores and its stabilization in an oriented configuration by photocrosslinking

AbstractA new photocrosslinkable polymer designed for application in second harmonic generation has been prepared and tested for frequency doubling of IR lasers. The polymer is based on a colorless polyurethane with pendant tolane nonlinear optical chromophores that carry a polymerizable styrene moiety at their extremities. Photocrosslinking is achieved by irradiation of films containing a small amount of a bleachable radical photoinitiator. The effect of photoinduced radical crosslinking on the mobility of the chromophores has been studied by recording the intensity of the frequency doubled light, generated by a poled sample, with increasing temperature. As expected, photocrosslinking leads to NLO materials with highly stable chromophore orientation.

Photophysical and photochemical behaviour of (( N,N-dimethylamino)methyl)styrenes

The photophysics and photochemistry of three different (( N,N-dimethylamino)methyl)styrenes, in which the methylene bridge is attached to different positions of the styrene moiety, have been investigated. Monomer fluorescence decay times are shorter than experimental time resolution (approximately 30 ps). Exciplex properties, e.g. fluorescence yields, are strongly dependent on the substitution pattern. In contrast with intermolecular exciplexes between corresponding methylstyrenes and triethylamine, the exciplex decay time increase with increasing solvent polarity. In addition to the intramolecular photophysical relaxation pathways, photochemical decomposition of the compounds was observed; a major product is the corresponding methylstyrene.

Radical polymerization of 4-methylene-2-phenyl-2-(4-vinylphenyl)-1,3-dioxolane as a bifunctional monomer containing differential reactivity

Polymerization of a bifunctional monomer, 4-methylene-2-phenyl-2-(4-vinylphenyl)-1,3-dioxolane (3), is described. 3 is anticipated to undergo polymerization of the styrene moiety, addition polymerization of the unsaturated cyclic monomer moiety, and elimination polymerization with formation of benzophenone derivative. However, selective polymerization of the styrene moiety of 3 is achieved in DMF solution, with complete retention of another radical polymerizable group as a pendant on side chain. Furthermore, bulk polymerization gave a crosslinked polymer and low concentration reaction caused back biting of its own side chain.

Photochemistry of 1-substituted 1,2-dihydro-1,4- dicyanonaphthalenes

The previously reported intramolecular photocycloaddition of 1-allyl-1,2-dihydro-1,4-dicyanonaphthalene ( 4) is a triplet process. The corresponding 1-benzyl derivative ( 6) is photochemically inert, whereas the two diastereoisomeric 1-(1-acenaphthenyl derivatives ( 7 and 8) react through the triplet (localized on the styrene moiety) by hydrogen abstraction and closure of the diradical to form products containing an additional ring ( 9 and 10 respectively).

Photochemical Reactions of 4-Acylstyrenes. Effects of Acyl Substituents on Photocyclodimerization via an Excited Triplet State

Abstract The photochemical reactions of 4-acylstyrenes (1a–e; acyl = acetyl, benzoyl, 1-naphthoyl, 2-naphthoyl, and 9-phenanthrylcarbonyl, respectively) were investigated, and their excited state behavior and photoreactivities are discussed in relation to the aryl ketone structures. Photoirradiation of 1a–e in benzene gave two isomeric cyclodimers of trans- and cis-1,2-bis(4-acylphenyl)cyclobutanes(2a–e and 3a–e) as main products, accompanied by the formation of some oligomers and polymers. The fractions of the trans-form in the cyclodimers were ca. 80%; this indicated that the cyclodimerization proceeded via the π,π* triplet state. The quantum yields of the photodimerization for 1a–e were almost the same irrespective of the acyl substituents (Φ = 0.03–0.04 at [1a–e] = 0.1 mol dm−3). Phosphorescence spectra of 1c (τ = 0.48 s) and 1d (τ = 0.91 s) observed in a rigid solution at 77 K, which coincided with those of the respective model aryl ketones, were ascribed to the low-lying excited π,π* triplet states localized on the naphthalene moiety of the molecules. Phosphorescence emissions of 1a and 1b could not be detected. The transient absorption spectrum of 1d (τ = 23 ns) observed in a fluid solution at 293 K was tentatively assigned to the π,π* triplet state mainly localized on the styrene moiety of the molecule. The photoreaction mechanism is discussed in terms of the intramolecular triplet energy transfer.

Thermal degradation aspects of model copolymers based on styrene, maleic anhydride, diethyl maleate and diethyl fumarate

Three copolymers, poly(styrene-maleic anhydride), poly(styrene-diethyl fumarate) and poly(styrene-diethyl maleate) were pyrolysed isothermally at 450 °C for 30 min in a nitrogen atmosphere. The pyrolysis products were separated and identified with a gas chromatograph coupled to a mass spectrometer. In the case of poly(styrene-maleic anhydride) and poly(styrene-diethyl fumarate) toluene, ethylbenzene and styrene were detected as the major pyrolysis products from the styrene moiety. In the case of poly(styrene-diethyl maleate), dimers and trimers of styrene were detected among the pyrolysis products. These results agree well with the conclusions from the IR studies and the reported copolymerisation parameters of the monomers. On-line pyrolysis experiments of poly(styrene-maleic anhydride) showed that the incorporated maleic anhydride units degrade at a temperature around 80 °C lower than the polymer backbone.

Photopolymerization of monolayers prepared from surfactants containing styrene moieties

Monolayers on aqueous surfaces have been prepared from positively and negatively charged synthetic surfactants: bis(2-(n-hexadecanoyloxy)ethyl)methyl(p-vinylbenzyl)ammonium chloride (1), di-n-octadecylmethyl(p-vinylbenzyl)ammonium chloride (2), di-n-octadecylmethyl(2-((4-vinylbenzoyl)oxy)ethyl)ammonium chloride (3), n-hexadecyl 11-(4-vinylbenzamido)undecyl hydrogen phosphate (4), and dioctadecyldimethylammonium bromide (5). Surface pressure-surface area, surface potential-surface area, and surface ellipsometry-surface area isotherms have led to values for collapse areas (A{sub c}) and collapse pressures (P{sub c}) of 35 {angstrom}{sup 2}/molecule and 67 mN/m, 55 {angstrom}{sup 2}/molecule and 40 mN/m, 70 {angstrom}{sup 2}/molecule and 42 mN/m, 33 {angstrom}{sup 2}/molecule and 54 mN/m, and 42 {angstrom}{sup 2}/molecule and 50 mN/m for monolayers prepared from 1-5, respectively. Ultraviolet irradiation of monolayers prepared from 1-4 resulted in their photopolymerization. The A{sub c} value decreased upon polymerization of monolayers prepared from 1 and 2, but it increased for monolayers prepared from 4. A similar trend was observed in the surface potential and ellipsometric measurements. Kinetics of photopolymerization of monolayers prepared from 1 have been investigated in detail. Rate constants for the photopolymerization, initiated by steady-state and pulsed-laser irradiations, have been determined at different surface pressures and irradiation energies. The obtained data have been analyzed in terms of a two-dimensional patch-polymerization model (PPM) and by the classical approach considering photoinitiation, propagation, and termination rates (CPM).more » Both models predict a first-order change of the monolayer surface area as a function of irradiation time.« less

A comparative study of the thermal degradation of unsaturated polyester resins containing various chlorinated norbornene dicarboxylic acid units in the backbone: Part II. The fate of the styrene moiety

Pure polystyrene and styrene-cured unsaturated polyesters made from different chlorinated norbornene dicarboxylic acids, 1,2-propanediol and maleic anhydride were pyrolysed in vacuo and in a nitrogen atmosphere. The pyrolysis products were separated and identified with a gas chromatograph coupled with a mass spectrometer. The results showed the influence of the chlorine radicals evolved during pyrolysis on the products and the product distribution pattern resulting from the styrene moiety.

Intramolecular [2 + 2] photocycloaddition. 2. Mechanism of intramolecular photocyclization of α,ω-bis(p-vinylphenyl)alkanes

From the photophysical measurements of the title reaction, the formation of cyclophanes is concluded to be facilitated by high microscopic concentration of styrene moieties and depressed by strain loaded at the transition state.

Formation and characterization of microcrystalline semiconductor particles on bilayer lipid membranes

Microcrystalline cadmium, indium, copper, and zinc sulfides were generated in situ on the surface of bilayer lipid membranes (BLMs) prepared from bovine-brain phosphatidylserine (PS), glyceryl monooleate (GMO), and a synthetic, polymerizable surfactant (n-C/sub 15/H/sub 31/CO/sub 2/(CH/sub 2/)/sub 2/)/sub 2/N/sup +/(CH/sub 3/)CH/sub 2/C/sub 6/H/sub 4/CH double bond CH/sub 2/, Cl/sup -/ (STYRS). Semiconductor-containing BLMs remained stable for days. Semiconductor formation on the BLM surface was monitored by optical microscopy, voltage-dependent capacitance measurements, and absorption and intracavity-laser-absorption spectroscopy. Band gap excitation of GMO- BLM-incorporated CdS resulted in the development of photovoltage. Irradiation of CdS incorporated into BLMs formed from STYRS (using a 350-nm cutoff filter) led to absorption losses due to the styrene moiety in the surfactant. Apparently, CdS sensitized the photopolymerization of STRYS BLMs.

Composition dependence of glass transition temperature of sulfonated‐polystrene ionomers

AbstractThe glass transition temperatures of alkali (Na, K, Rb, Cs) and alkaline‐earth (Ba, Sr, Ca, Mg) ionomers of sulfonated polystyrenes (PSSA) with 3.4, 6.9, 12.7, and 16.7% of the styrene moieties sulfonated are reported. For the alkali‐metal PSSA ionomers, Tg depends on the degree of sulfonation, at least up to 13%, but not strongly on the nature of the cation. For the alkaline‐earth analogs Tg does not depend strongly on either the cation or the degree of sulfonation until the 16.7% level is reached. These and other reported data are discussed in terms of the role of cations in determining morphology.