Biphenyl Side Groups Research Articles

DEVELOPMENT OF BIPHENYL MONOMERS AND ASSOCIATED CROSSLINKED POLYMERS WITH INTRAMOLECULAR PI-PI INTERACTIONS.

Monomers containing biphenyl moieties were employed to create two sets of covalently crosslinked polymers that displayed noncovalent interactions in their 3-dimensional network. The biphenyls (precursors) used were 2-phenylphenol, 4-phenylphenol and 4,4'-dihydroxybiphenyl, and their acrylated forms were synthesized and named as 2-phenylphenolmonoacrylate (2PPMA), 4-phenylphenolmonoacrylate (4PPMA), and 4,4'-dihydroxybiphenyldiacrylate (44BDA), respectively. These were characterized by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) to confirm the successful acrylation reaction. Polymers were synthesized via free radical polymerization reactions with varying crosslinker contents, and their network properties were characterized using swelling studies and compressive modulus tests. Interestingly, swelling studies did not show the expected decreasing swelling ratio with increasing crosslinker content, while compression testing indicated the expected trend of increasing modulus with increasing crosslinking density. The unexpected swelling results are hypothesized to result from the intramolecular interactions between the biphenyl side groups that result in noncovalent crosslinks.

Significantly Enhanced Molecular Stacking in Ternary Bulk Heterojunctions Enabled by an Appropriate Side Group on Donor Polymer.

Ternary strategy is a promising approach to broaden the photoresponse of polymer solar cells (PSCs) by adopting combinatory photoactive blends. However, it could lead to a more complicated situation in manipulating the bulk morphology. Achieving an ideal morphology that enhances the charge transport and light absorption simultaneously is an essential avenue to promote the device performance. Herein, two polymers with different lengths of side groups (P1 is based on phenyl side group and P2 is based on biphenyl side group) are adopted in the dual‐acceptor ternary systems to evaluate the relationship between conjugated side group and crystalline behavior in the ternary system. The P1 ternary system delivers a greatly improved power conversion efficiency (PCE) of 13.06%, which could be attributed to the intense and broad photoresponse and improved charge transport originating from the improved crystallinity. Inversely, the P2 ternary device only exhibits a poor PCE of 8.97%, where the decreased device performance could mainly be ascribed to the disturbed molecular stacking of the components originating from the overlong conjugated side group. The results demonstrate a conjugated side group could greatly determine the device performance by tuning the crystallinity of components in ternary systems.

2B05 側鎖にビフェニル基をもつポリ(α-フルオロアクリレイト)の液晶相転移(化学・材料)

2B05 側鎖にビフェニル基をもつポリ(α-フルオロアクリレイト)の液晶相転移(化学・材料)

Preparation of poly(ether ketone)s having phenyl, biphenyl, and terphenyl side groups and comparison of their properties

Three kinds of bis(aromatic fluoride) compounds, 3,5-bis(4-fluorobenzoyl)biphenyl (1), 3,5-bis(4-fluorobenzoyl)-1,1′:4′,1″-terphenyl (2), and 3,5-bis(4-fluorobenzoyl)-1,1′:4′,1″:4″,1′′′-quaterphenyl (3), were synthesized by cross-coupling of the corresponding triflates with phenylboronic acid. Linear poly(ether ketone)s (1x, 2x, and 3x) having phenyl, biphenyl, and terphenyl side groups, respectively, were prepared by the polycondensation of the bis(aromatic fluoride) compounds with bisphenol A (a) and 4,4′-dihydroxybiphenyl (b) in N-methyl-2-pyrrolidone. The obtained poly(ether ketone)s were characterized by X-ray diffraction, differential scanning calorimetry, and thermogravimetry. The structure–property relationships of these poly(ether ketone)s were examined and compared with those of poly(ether ketone)s (4x) having no side group, which were prepared from 3,5-bis(4-fluorobenzoyl)benzene (4). The properties of the poly(ether ketone)s, solubilities, and thermal properties were compared and discussed based on the length of the side groups.

Polarization axis-selective realignment of a photoreactive liquid crystalline composite with homogeneous alignment

We investigated the photoalignment properties of a liquid crystalline composite. The composite consisted of a low molecular weight nematic liquid crystal (LC) and a photoreactive liquid crystalline polymer containing 4-(4-methoxycinnamoyloxy)biphenyl side groups. Homogeneously aligned LC composite cells were fabricated using rubbed substrates and were then exposed to a linearly polarized (LP) ultraviolet (UV) laser beam. The alignment states of the LC composites were characterized using a LP visible laser beam. The LC composite in the cell was realigned by LP UV exposure and subsequent annealing. The direction of the realignment could be controlled by the polarization direction of the LP UV beam. The relationship between the realignment direction and the rubbing strength of the substrates was also investigated. A large realignment was induced in the LC composite cell when the azimuthal anchoring strength of the rubbed substrates was relatively weak.

Photoalignment and resulting holographic vector grating formation in composites of low molecular weight liquid crystals and photoreactive liquid crystalline polymers

Polarization holographic gratings were formed in liquid crystal (LC) cells fabricated from a mixture of low molecular weight nematic LC and a photoreactive liquid crystalline polymer (PLCP) with 4-(4-methoxycinnamoyloxy)biphenyl side groups. The diffraction properties of the gratings were analyzed using theoretical models which were determined based on the polarization patterns of the polarization holography. The results demonstrated that vector gratings comprised of periodic orientation distributions of the LC molecule were induced in the cells based on the axis-selective photoreaction of the PLCP. The vector gratings were erased by applying a sufficiently high voltage to the cells and then were reformed with no hysteresis after the voltage was removed. This phenomenon suggested that the PLCP molecules were stabilized based on the axis-selective photocrosslink reaction and that the LC molecules were aligned by the photocrosslinked PLCP. This LC composite with axis-selective photoreactivity is useful for various optical applications, because of their stability, transparency, and response to applied voltage.

On/off switching of structural color by using multi-bilayered films containing copolymers having azobenzene and biphenyl side groups

In this paper, the change in structural color of multi-bilayered films fabricated by stacking copolymers, PMAz–PMBP (m : ), consisting of azobenzene and biphenyl side chain groups, and polyvinyl alcohol (PVA) alternately, was investigated.

Molecular Reorientation Behavior of Photocrosslinkable Liquid Crystalline Copolymer Films Composed of 4-(4-Methoxycinnamoyloxy)biphenyl and Phenylester Side Groups

The cooperative molecular reorientation in methacrylate copolymer films comprising photoreactive 4-(4-methoxycinnamoyloxy)biphenyl and phenylester in their side chains was investigated by irradiation with linearly polarized ultraviolet light and subsequent annealing. Both cinnamate and phenylester side groups were miscible in the copolymer composition, and axis-selective photoreaction of the cinnamate groups was observed. Thermally enhanced cooperative in-plane orientation of both side groups was obtained when the irradiated films were annealed in the liquid crystalline temperature range of the copolymers.

Simple fabrication of liquid crystalline grating cells with homogeneous and twisted nematic structures and effects of orientational relaxation on diffraction properties.

We have substantiated a simple yet efficient, competitive, and practical method to automatically fabricate liquid crystalline grating cells with homogeneous or twisted nematic (TN) structures by one-step ultraviolet holographic exposure on an empty glass cell coated with a photocrosslinkable polymer liquid crystal with 4-(4-methoxycinnamoyloxy)biphenyl side group (P6CB) films. The polarization diffraction properties in the resultant liquid crystalline grating cells have also been investigated extensively by varying the grating pitch. The theoretical considerations on the basis of elastic continuum theory revealed that accumulation of elastic free-energy density due to the TN structure affected the diffraction properties, although the strong anchoring of our photoalignment material contributed effectively to form the expected spatial distribution of liquid crystalline directors in the grating cells.

Polymeric microstructures and dielectric properties of polynorbornenes with 3,5-bis(trifluoromethyl)biphenyl side groups by ring-opening metathesis polymerization

exo-Polynorbornenes containing bis(trifluoromethyl)biphenyl side groups were synthesized by ring-opening metathesis polymerization using different Grubbs' catalysts, the microstructures of the polymer chains were established using NMR and IR spectroscopy. The influence of monomer and catalyst structures on chain microstructure was revealed and the correlation of properties with microstructure was investigated in detail. The exo-poly(N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine) (exo-PTNP) and exo-poly(N-3,5-bis(trifluoromethyl)biphenyl-norbornene-dicarboximide) (exo-PTNDI) formed using Ru-I show a trans double bond bias of 67% and 83%, respectively, whereas the corresponding polymers formed using Ru-III have lower contents of trans double bond, 30% and 50%, respectively. Compared to the highly trans endo-PTNP formed using Ru-I, which is isotactic and has a dielectric constant of about 20, the endo-PTNP formed using Ru-III, the exo-PTNDIs and the exo-PTNPs formed using Ru-I and Ru-III all have different proportions of trans and cis double bonds, they are atactic and display relatively low dielectric constants, in the range 6 to 9. DSC measurements indicate some dependence of Tg, varying 161 to 221 °C, on tacticity and cis/trans ratios with higher trans contents tending towards higher Tg. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4786–4798

Inter- and Intramolecular Interactions in Triptycene-Derived Bisphosphite Hydroformylation Catalysts: Structures, Energies, and Caveats for DFT-Assisted Ligand Design

The hydroformylation catalyst (L)RhH(CO)2, with a triptycene-derived bisphosphite ligand, and its iridium analogue were studied in solution, in the solid state, and computationally (DFT) in order to determine their molecular structures and to understand the equilibria between isomers. The predicted intramolecular distance of the two biphenyl side groups of these ligands strongly depends upon the treatment of inter- and intramolecular noncovalent interactions. A balanced treatment of these “weak” interactions is a prerequisite for obtaining reasonable structures and consequently also for determining relative energies of the different P-coordination modes. Low-temperature NMR studies confirm the equilibrium between axial–equatorial and equatorial–equatorial isomers in solution and have been used to estimate their relative stability in the equilibrium.

High dielectric performance of tactic polynorbornene derivatives synthesized by ring‐opening metathesis polymerization

AbstractFunctional polynorbornenes (PNBEs) containing pyrrolidine moiety and bis(trifluoromethyl)biphenyl side group were synthesized via ring‐opening metathesis polymerization (ROMP), and the microstructure of polymer chain was characterized by NMR spectroscopy. Poly(N‐3,5‐bis(trifluoromethyl)biphenyl‐norbornene‐pyrrolidine) (PTNP) and poly(N‐phenyl‐norbornene‐pyrrolidine) (PPNP) are supposed to have practically trans double bonds and adopt isotactic syn conformation, whereas poly(N‐3,5‐bis(trifluoromethyl)biphenyl‐norbornene‐dicarboximide) (PTNDI) has both trans and cis double bonds and atactic microstructure. PTNP, PTNDI, and PPNP have much different dielectric constants of 20, 7, and 3, respectively, which is attributed to both the polar 3,5‐bis(trifluoromethyl)biphenyl group and the stereoregular chain structure. The existence of rigid pyrrolidine moiety has a positive contribution to form the tactic polymer chain during ROMP. Polymers are highly thermal stable up to ∼300 °C. Having good dielectric properties and thermal stability, these functional PNBEs are expected as the potential dielectric material in thin film capacitors. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Rigid bio-foam plastics with intrinsic flame retardancy derived from soybean oil

Acrylated epoxidized soybean oil was chemically grafted with difunctional flame retardants carrying phosphorus, double bonds or biphenyl groups, and then copolymerized with styrene to produce bio-foams with high mechanical properties and intrinsic flame resistance. Owing to the introduction of rigid comonomer, phosphorus, additional double bonds or biphenyl side groups, the bio-foams showed compressive strength similar to that of conventional unsaturated polyester foam, antiflaming capability and biodegradability as well. More importantly, the modified flame retardant partially took the role of styrene, leading to a lower fraction of petroleum based substance in the bio-foams without the expense of foam strength, and improved biodegradability. The comparison between the bio-foams with intrinsic flame retardancy on a molecular level and those containing inflaming retardant fillers revealed that the latter have acquired rather poor mechanical properties and hence are obviously inferior to the former in practical applications where a load-bearing capability is required.

Liquid Crystal Alignment Properties on Polyamide Films Bearing a Phenylenediacryloyl Moiety in the Main Chain

Soluble photosensitive polyamide, which has a photoreactive 1,4-phenylenediacryloyl (PDA) moiety in the main chain with biphenyl side groups, was synthesized with high molecular weights. The polymer produced high quality films through conventional spin-casting and dry processing with relatively good thermal stability. The photochemical reactions of the polyamide in the films were investigated by UV-Vis spectroscopy; the polymer in the film demonstrated excellent photoreactivity to UV light. Linearly polarized ultra-violet light (LPUVL) irradiation induced anisotropic reorientations of the polymer chains in the film as a result of direction-selective photoreaction of the PDA moieties. The polyamide thin films were found to have excellent unidirectional orientation ability as a result of photo-exposure with LPUVL; the direction-selective photoreaction of the PDA moiety in the main chains induced alignment of nematic liquid-crystals (LCs) on the surface. The pretilt behaviors of the LC molecules on the LPUVL irradiated film surfaces were controlled by both the exposure dose of LPUVL and the annealing temperature.

High in-plane alignment of liquid crystalline methacrylate copolymers bearing photoreactive 2-styrylpyridine and mesogenic 4-methoxybiphenyl groups

This paper describes the thermally enhanced in-plane alignment and other properties of liquid crystalline (LC) copolymers (1, 2, and 3) consisting of a methacrylate with a 2-styrylpyridine side group as a photocyclodimerizable group and a methacrylate with a methoxy biphenyl side group as a mesogenic group. 1H NMR spectroscopy indicated that the contents of the photoreactive monomer unit in copolymers 1, 2, and 3 were 0.65, 0.46 and 0.19 (mole fraction), respectively. The copolymers in the film showed a transmittance of 92% at wavelengths > 450 nm, even at 100 °C, as well as thermal stability up to approximately 360 °C. Copolymers 1 and 2 gave a nematic texture at 155 and 150 °C, respectively, while copolymer 3 showed a smectic texture at 130 °C. The copolymer films aligned parallel to the linearly polarized UV(LPUV) light after LPUV light irradiation and subsequent thermal annealing. The respective in-plane order parameters of copolymers 1, 2, and 3 in the film at 315 nm were 0.65 at 0.001 J/cm2, 0.59 at 0.01 J/cm2, and 0.48 at 0.025 J/cm2 by the same treatment in the LC temperature ranges. This suggests that the photoreactive LC copolymers not only have high optical transparency and good thermal stability but also have controllable, high in-plane alignment with the contents of the photoreactive monomer unit.

Effect of Spacer Length on Photoinduced Reorientation Behavior of Photocrosslinkable Liquid Crystalline Polymer Films Comprising 4-(4-Methoxycinnamoyloxy)biphenyl Side Groups

Methacrylate polymer liquid crystals containing 4-(4-methoxycinnamoyloxy)biphenyl (MCB) side group with different alkylene spacer length between the polymethacrylate backbone and MCB side groups are synthesized. Influence of the alkylene spacer length on the thermally enhanced molecular reorientation behavior of thin films is investigated using linearly polarized ultraviolet (LPUV) light exposure and subsequent annealing. In-plane reorientation preferentially occurs when the alkylene spacer is short, and the induced in-plane order parameter is greater than 0.6. On the other hand, when the alkylene spacer is long, thermally induced out-of-plane reorientation is observed as well as the in-plane reorientation.

Thermally enhanced photoinduced in‐plane reorientation in photo‐cross‐linkable polymer liquid crystalline films and its application to linear polarizer

AbstractThermally enhanced photoinduced in‐plane molecular reorientation in new photo‐cross‐linkable polymer liquid crystalline (PPLC) films comprising 4‐[ω‐(4‐methoxycinnamoyloxy)alkyloxy]biphenyl side groups is explored using linearly polarized ultraviolet (LPUV) light exposure and subsequent annealing. The influence of the alkylene spacer length between the photo‐cross‐linkable group and the biphenyl mesogenic moiety is investigated. The straight‐line characteristics of the photoreactive mesogenic side group and the 4‐methoxycinnamoyl group play important roles in the high photoreactivity and the large thermally enhanced molecular reorientation, where the in‐plane order and the birefringence of the reoriented film are 0.61 and 0.18 are obtained. Finally, cooperative molecular reorientation of dichroic dyes doped in PPLC films is also achieved to fabricate a linear polarizer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4712–4718, 2008

Chiral liquid-crystalline copolyacrylates with biphenyl and phenyl benzoate side groups

The phase behavior and structure of liquid-crystalline phases of three series of copolymers with mesogenic units belonging to the families of biphenyls and phenyl benzoates have been studied, with the former mesogenic units containing a chiral center in a flexible spacer. A variation in the isotropization temperature as a function of composition is well described by the additivity rule, whereas the tilt angle of mesogenic groups in smectic layers changes nonlinearly. This angle decreases beginning from homopolymers and attains the minimum value for the copolymers of the equimolar composition, which show the highest ferroelectric activity among the polymer systems under study.

側鎖にビフェニル基をもつポリ(α-フルオロアクリレ－ト)の合成と相転移：α位のフッ素の液晶相に対する影響

側鎖にビフェニル基をもつポリ(α-フルオロアクリレ－ト)の合成と相転移：α位のフッ素の液晶相に対する影響

Synthesis and characterization of new aromatic polyesters containing biphenyl side groups

AbstractAromatic polyesters containing biphenyl side groups were synthesized by phase‐transfer catalyzed interfacial polycondensation of 1‐(4‐biphenylyl)‐1,1‐bis(4‐hydroxyphenyl) ethane (BBHPE) with terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), and a mixture of TPC/IPC (50 : 50 mol ratio). Copolyesters were synthesized by utilizing different molar proportions of BBHPE and 4,4′‐isopropylidenediphenol (BPA) with IPC and TPC. The inherent viscosities of polyesters were in the range 0.44–1.26 dL/g. All the polyesters were soluble in organic solvents such as dichloromethane, chloroform, tetrahydrofuran, meta‐cresol, pyridine, N,N‐dimethylformamide, N,N‐dimethylacetamide, and 1‐methyl‐2‐pyrrolidinone. Tough, transparent, and flexible films could be cast from chloroform solutions of these polyesters. WAXD measurements indicated that all the polyesters and copolyesters were amorphous in nature. Glass transition temperature of polyesters were in the range 198–256°C, while the initial degradation temperature of polyesters were in the range 444–481°C. Copolyesters derived from BBHPE exhibited improved solubility and higher glass transition temperatures compared to the corresponding polyesters based on BPA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007