Polystyrene Derivatives Research Articles

Conformational Studies of Covalently Grafted Poly(ethylene glycol) on Modified Solid Matrices Using X-ray Photoelectron Spectroscopy

Amine functionalized poly(ethylene glycols) (PEGs) with molecular weights 2000 and 4000 Da were covalently grafted onto carboxy modified hydrophilic Sephadex derivatives and hydrophobic polystyrene derivatives using anhydrous amine conjugation methods. Varying PEG surface concentration and layer thickness were achieved by controlling the reaction parameters and were analyzed by X-ray photoelectron spectroscopy (XPS). C-O intensities obtained from high resolution C 1s scans were correlated using the standard overlay model to study the grafting kinetics as well as conformational properties of grafted polymer chains. A detailed and systematic comparison of PEG layer thickness and distance between grafted chains with the Flory radius of surface grafted PEG resulted in valuable information regarding conformational behavior of the polymer. The influence of the nature of the solid matrix on grafting kinetics and conformational properties of the grafted polymer chain was also established from the XPS results.

Sequential double click reactions: a highly efficient post-functionalization method for optoelectronic polymers

A new post-functionalization method based on the Huisgen's 1,3-dipolar cycloaddition between azides and alkynes, followed by the atom-economic addition reaction between electron-rich alkynes and tetracyanoethylene (TCNE) was developed to introduce the donor–acceptor chromophores into polystyrene derivatives in remarkably high yields.

Liquid crystal alignment properties of polystyrene derivatives containing fluorinated side groups

The liquid crystal (LC) alignment properties of a series of polystyrene derivatives containing various fluorinated side chain terminal moieties, such as 4-fluorophenoxymethyl, 3,4,5-trifluorophenoxymethyl, pentafluorophenoxymethyl, and 4-trifluoromethoxyphenoxymethyl groups, were investigated. These polymers could induce homeotropic and/or homogeneous planar LC alignment on their surfaces by changing the LC molecules and rubbing conditions. For example, when a positive (MJ001929 from Merck) and negative dielectric anisotropic LC mixture (MLC-7026-000 from Merck) were used, homeotropic LC alignment was observed in the LC cells made from unrubbed films of pentafluorophenoxymethyl- and 4-trifluoromethoxyphenoxymethyl-substituted polystyrenes with a smaller surface energy, whereas random planar LC alignment was observed in those made from the other polymers with a larger surface energy. On the other hand, homeotropic LC alignment behavior was observed in all the LC cells made from unrubbed films of all the polystyrene derivatives when 5CB was used as the LC material.

PVT properties of linear and dendritic polymers

The aim of this article is to examine the limits of applicability of the Simha-Somcynsky (S-S) equation of state (EOS) by comparing the pressure-volume-temperature (PVT) data and the derivatives (compressibility, κ, and thermal expansion coefficient, α) of anionic linear polystyrene (PS) with poly(benzyl ether) dendrimers (PBED). Fitting the PVT of PBED data to the S-S EOS was similarly satisfactory as that of PS and the computed Lennard-Jones (L-J) interaction parameters showed similar errors of ca. 1%. Next, the experimental derivatives, α and κ of PS and PBED were compared with these functions computed from the S-S EOS—good agreement was obtained for α at ambient pressure, P, indicating validity of the S-S theory at least up to the first derivative. While the predicted κ = κ(P) dependence for PS and a linear PBED homologue was correct, for dendrimers the compressibility was higher at low pressure and it was lower at high P than theory predicts. Also the extracted values of the L-J repulsion volume, v*, between a segment pair was smaller than expected. The specific architecture of dendrimer molecules is responsible for this behavior, since their 3D configuration is significantly different from the S-S model with uniform segmental density and oxygen bonds in the main and side chains add flexibility. © 2009 NRC Canada. J Polym Sci Part B: Polym Phys 48: 322–332, 2010

Non-volatile Memory Devices Based on Polystyrene Derivatives with Electron-Donating Oligofluorene Pendent Moieties

We report bistable non-volatile memory devices based on polystyrene derivatives containing pendent electron-donating mono-, di-, and tri(9,9-dihexylfluorene), which are denoted as poly(St-Fl), poly(St-Fl(2)), and poly(St-Fl(3)), respectively. The effects of the oligofluorene chain lengths and polymer surface structures on the memory characteristics were explored. Poly(St-Fl)-, poly(St-Fl(2))-, and poly(St-Fl(3))-based devices exhibited a flash memory characteristic with different turn-on threshold voltages of 2.8, 2.0, and 1.8 V, respectively, which was on the reverse trend with the highest occupied molecular orbital levels of -5.86, -5.80, and -5.77 eV. Moreover, the memory device showed a high ON/OFF current ratio of 2.5 x 10(4) and a long retention time of 10(4) s. The possible mechanism of the switching behavior was explained by the space-charge-limited-current theory and filamentary conduction. The larger aggregation domain size of the polymer thin film processed from the mixed solvent of chlorobenzene/N,N-dimethylformamide probably promoted the diffusion of the Al atoms into the polymer film and formed the conduction channel. Thus, it significantly reduced the turn-on threshold voltage on the studied polymer memory devices. The present study suggested that the polymer memory characteristics could be efficiently tuned through the pendent conjugated chain length and surface structures.

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

We synthesized a series of polystyrene derivatives containing various side chain terminal moieties, such as phenoxymethyl, 4-methoxyphenoxymethyl, 4-fluorophenoxymethyl, 4-methylphenoxymethyl, and 4-trifluoromethoxyphenoxymethyl groups, using polymer analogous reactions, in order to investigate the effect of the side group on their liquid crystal (LC) alignment behaviors. The polymers containing 4-fluorophenoxymethyl, 4-methylphenoxymethyl, or 4-trifluoromethoxyphenoxymethyl side groups had lower surface energy values and the LC cells fabricated using the unrubbed films of these polymers showed homeotropic LC alignment behavior. The LC cells fabricated using the rubbed films of the polymers containing phenoxymethyl or 4-fluorophenoxymethyl groups showed homogeneous planar LC alignment behavior in which the LCs were aligned perpendicular to the rubbing direction. This homogeneous planar and perpendicular alignment behavior was ascribed to the favorable anisotropic interactions between the LC molecules and the side groups preferentially oriented perpendicular to the rubbing direction.

Liquid crystal alignment property of polystyrene derivatives containing dual photoreactive side groups

We synthesized a series of polystyrene derivatives having the dual photoreactive side moieties, 4-(4-cyanophenylazo)phenoxymethyl and methyl cinnamate-4-oxymethyl, for the application of photoalignment materials. Stable and homogeneous planar LC cells having pretilt angles adjustable from 0.5° to 5° were obtained from these polymer films having molar contents of cinnamate and azobenzene groups in the ranges of 100–80 and 0–20mol%, respectively, through the irradiation of linearly polarized ultraviolet (LP-UV) light to crosslink the cinnamate groups, followed by the irradiation of linearly polarized visible (LP-Vis) light to induce the isomerization of the azobenzene groups. The electro-optical and LC alignment properties of the LC cells were found to be affected by the molar composition of the photoreactive side groups and the exposure energies of LP-UV and LP-Vis light.

Synthesis of 1H‐quinazoline‐2,4‐diones from 2‐aminobenzonitriles by fixation of carbon dioxide with amidine moiety supported polymer at atmospheric pressure

Abstract1H‐Quinazoline‐2,4‐diones, which are key intermediates in the synthesis of medicines, were successfully synthesized from 2‐aminobenzonitriles by the fixation of CO2 in the presence of a polystyrene derivative bearing amidine moiety [poly(amidine)]. A model reaction, that is, the reaction of 2‐aminobenzonitrile (1a) with CO2 in the presence of N‐methyltetrahydropyrimidine (MTHP) revealed that a catalytic amount of MTHP afforded 1H‐quinazoline‐2,4‐dione (2a) quantitatively at atmospheric pressure. Several 1H‐quinazoline‐2,4‐diones (2a‐2c) were successfully synthesized from the corresponding 2‐aminobenzonitriles (1a‐1c) in the presence of poly(amidine). The poly(amidine) could easily be separated from the reaction mixture by filtration and reused in subsequent reactions owing to the heterogeneous system. These demonstrated that poly(amidine) is a useful heterogeneous polymer‐supported reagent for the synthesis of 1H‐quinazoline‐2,4‐diones from CO2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 653–657, 2009

Relaxation times and energy barriers of rubbing-induced birefringence in glass-forming polymers

The relaxations of rubbing-induced birefringence (RIB) in several glass-forming polymers, including polycarbonate and polystyrene (PS) derivatives with various modifications to the phenyl ring side group, are studied. Significant relaxations of RIB are observed at temperatures well below the glass transition temperature T (g) . The relaxation times span a wide range from approximately 10 s to probably geological time scale. Physical aging effects are absent in the RIB relaxations. The model proposed for the interpretation of RIB in PS describes well the RIB relaxations in all the polymers investigated here. The energy barriers are of the order of a few hundred kJ/mol and decrease with decreasing temperature, in opposition to the trend of Vogel-Fulcher form for polymer segmental relaxations above T (g) . The relaxation behaviors of different polymers are qualitatively similar but somewhat different in quantitative details, such as in the values of the saturated birefringence, the shape of the initial barrier density distribution functions, the rates of barrier decrease with decreasing temperature, and the dependence of relaxation times on temperature and parameter xi , etc. The RIB relaxations are different from any of the other relaxations below T (g) that have been reported in the literature, such as dielectric relaxations or optical probe relaxations. A microscopic model for the relaxations of RIB is much desired.

Synthesis of a polypseudorotaxane, polyrotaxane, and polycatenane using ‘click’ chemistry

The synthesis of a polypseudorotaxane, polyrotaxane, and polycatenane containing the electron-deficient cyclophane cyclobis(paraquat- p-phenylene) (CBPQT 4+) subunit in the side chain is described. These interlocked supramolecular polymers have been prepared from an azide-functionalized polystyrene derivative and an acetylene-functionalized [2]rotaxane, [2]catenane and their parent tetracationic cyclophane via Cu(I)-catalyzed 1,3 dipolar cycloadditions (‘click chemistry’). The synthesis and characterization of the polymers and intermediates has been described using IR, 1H NMR, UV spectroscopies, and voltammetry. We have shown that the CBPQT 4+ unit of the side chain polystyrene derivative has the ability to reversibly undergo complexation with a complementary dialkoxynaphthalene derivative.

Liquid crystal alignment properties of polystyrene derivatives containing coumarin side groups

The liquid crystal (LC) alignment properties of LC cells fabricated with films of polystyrene derivatives containing coumarin side groups (P7COU#, where # is the molar content of coumarin side groups in %) were investigated. Good optical transparency of the P7COU# films was observed in the visible light region. LC cells fabricated with rubbed P7COU# films with more than 51 mol. % of coumarin‐containing monomeric units exhibited LC alignment perpendicular with respect to the rubbing direction with a high azimuthal anchoring energy (1×10−5–7×10−5 J m−2). LC cells made from rubbed P7COU# films with more than 65 mol. % of coumarin‐containing monomeric units exhibited a shift of the LC alignment direction by approximately 10° compared with those made from a polystyrene film. The electro‐optical performance of the LC cells fabricated with the rubbed P7COU82 film was found to be as good as that of the LC cells fabricated with a rubbed polyimide film.

Synthesis and dielectric properties of photoreactive polystyrene containing [1-(3-isopropenyl-phenyl)-1-methyl-ethyl]-carbamate in the side chain

Novel polystyrene derivatives comprising [1-(3-isopropenyl-phenyl)-1-methyl-ethyl]-carbamate in the side chain were synthesized as photoreactive copolymers. Poly(4-vinylphenol) was made to react with 1-(1-isocyanato-1-methyl-ethyl)-3-isopropenyl-benzene (m-TMI) and the unreacted hydroxyl groups were protected with acetyl chloride. The copolymers are highly sensitive to the radical photoinitiators that can be activated by irradiation of UV light (λ = 300–365 nm). FTIR spectroscopy was employed to monitor the structural changes in the copolymers exposed to UV irradiation. The dielectric properties of the copolymers were investigated by measuring the capacitance and calculating the permittivity as a function of frequency, along with the I–V characteristics. Their properties were compared with those of thermally crosslinkable poly(4-vinylphenol) blended with poly(melamine-co-formaldehyde), which is frequently used as a dielectric layer in organic field-effect transistors (OFETs). No significant dielectric dispersion was observed in the frequency range of 1 kHz–1 MHz. The dielectric constant was determined to be in the range of 4.2–6.0, which offers a potential for the application of these copolymers to OFET gate insulators. These soluble dielectrics exhibit good film uniformity and can also be patterned using a standard photolithographic technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1710–1718, 2008

Gold–platinum bimetallic clusters for aerobic oxidation of alcohols under ambient conditions

We have developed gold/platinum alloyed bimetallic cluster catalysts supported on a cross-linked polystyrene derivative, which present much higher activity and selectivity than single metal gold or platinum clusters for aerobic oxidation of alcohols under ambient conditions.

Interaction of glycopolymers with human hematopoietic cells from cord blood and peripheral blood

Polystyrene derivatives, poly[N-pvinylbenzyl-O-D-glucopyranosyl-(1-4)-D-glucoamide] (PV Maltose) and poly[N-p-vinylbenzyl-O-mannopyranosyl-(1-4)-D-glucoamide] (PV Mannose), which contain glucose and mannose moieties, respectively, have the specific binding ability with murine hematopoietic cells. In this study, we confirm the ability of these glycopolymers to interact specifically with human hematopoietic stem cells (HSCs) and mature cells derived from human cord blood (CB) and peripheral blood (PB). Using fluorescence isothiocyanate (FITC)-labeled glycopolymers, we observed that 98% to 93% of hematopoietic cells interacted very strongly with PV Mannose, and 63% of CB and 29% PB interacted with PV Maltose. Both glycopolymers bound better to cells from CB than from PB. Cytotoxic studies revealed that a 0.1 mM dose of PV Mannose induced apoptosis in 20% CB cells, in contrast to 3-5% PB cells. Furthermore, we demonstrated that all of CD34(+) HSCs of both origins bound specifically to PV Mannose, whereas 33-47% bound to PV Maltose. In addition, the majority of B cells (CD19(+)), T cells (CD3(+)), monocytes (CD14(+)), and erythrocytes (CD235a(+)) bound to PV Mannose, but a lower percentage interacted with PV Maltose. In vivo study, bone marrow, spleen, and liver tissues in NOD-SCID mice injected with PV Mannose conjugated CB, were detected PV Mannose positive hematopoietic cells. These data suggest that the use of PV Mannose and PV Maltose might be used for gene and drug delivery for hematopoietic cells and thus, may be useful in therapeutic settings.

Polystyrene-supported borane complexes PS-BH2 • D

A polystyrene derivative in which the para-positions of the phenyl rings are selectively functionalised with BH2 moieties (PS-BH2) has been prepared from poly(4-trimethylsilyl styrene) through a series of polymer analogous reactions. The polymer was successfully isolated in the form of its polymeric acid-base complexes PS-BH2 • D (D = tBuPy, PPh2Me). The selective and nearly quantitative placement of the BH2 functionalities was confirmed by multi-nuclear NMR spectroscopy and IR spectroscopy. The thermal properties of the polymer complexes were investigated by differential scanning calorimetry and thermogravimetric analysis.

Enhanced, Perpendicular Liquid‐Crystal Alignment on Rubbed Films of a Coumarin‐Containing Polystyrene

AbstractWe synthesized a series of polystyrene derivatives containing coumarin side groups using polymer analogous reactions. The liquid‐crystal (LC) alignment director for these polymer films was found to be perpendicular to the rubbing direction. The contrast ratio and anchoring‐energy values of these polystyrene derivatives were found to be much greater than those of polystyrene and poly(chloromethylstyrene), indicating that the coumarin side groups increase the aligning ability. For example, the anchoring energy of a polymer with 82 mol‐% of coumarin‐containing monomeric units, compared to polystyrene, is about 7 × 10−5 J · m−2 and 1 × 10−7 J · m−2, respectively.magnified image

Aerobic Oxidation of Alcohols at Room Temperature and Atmospheric Conditions Catalyzed by Reusable Gold Nanoclusters Stabilized by the Benzene Rings of Polystyrene Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Inside Cover: Aerobic Oxidation of Alcohols at Room Temperature and Atmospheric Conditions Catalyzed by Reusable Gold Nanoclusters Stabilized by the Benzene Rings of Polystyrene Derivatives (Angew. Chem. Int. Ed. 22/2007)

Polymer-incarcerated gold nanoclusters catalyze the aerobic oxidation of various alcohols to aldehydes and ketones under ambient conditions. As described by S. Kobayashi and co-workers in their Communication on page 4151 ff., the nanoclusters were prepared by microencapsulation of gold in a copolymer based on polystyrene followed by cross-linking. The oxidation reactions catalyzed by the nanoclusters proceed without heating, with only molecular oxygen consumed and water generated as the sole side product.

Aerobic Oxidation of Alcohols at Room Temperature and Atmospheric Conditions Catalyzed by Reusable Gold Nanoclusters Stabilized by the Benzene Rings of Polystyrene Derivatives

Lock up your gold: Polymer-incarcerated gold nanoclusters (PI Au) were synthesized by microencapsulation of gold nanoclusters and cross-linking using a copolymer based on polystyrene (see TEM image). The nanoclusters could be used to catalyze the aerobic oxidation of alcohols to aldehydes and ketones under atmospheric conditions at room temperature, and additionally could be reused with little loss of activity.

Innentitelbild: Aerobic Oxidation of Alcohols at Room Temperature and Atmospheric Conditions Catalyzed by Reusable Gold Nanoclusters Stabilized by the Benzene Rings of Polystyrene Derivatives (Angew. Chem. 22/2007)

In einem Polymer gefangen sind die Goldnanocluster-Katalysatoren, die, wie S. Kobayashi et al. in ihrer Zuschrift auf S. 4229 ff. schildern, durch Mikroverkapselung von Goldnanoclustern und Vernetzen eines Polystyrol-Copolymers synthetisiert wurden. Diese Katalysatoren können zur aeroben Oxidation von Alkoholen zu Aldehyden und Ketonen unter Umgebungsbedingungen eingesetzt werden. Die Reaktion verläuft ohne zusätzliches Heizen; dabei wird nur O2 verbraucht, und als alleiniges Nebenprodukt entsteht Wasser.