Synthesis and properties of polynorbornenes bearing oligomeric siloxane pendant groups

The ring-opening metathesis polymerization (ROMP) of norbornene derivatives 1-5 bearing oligomeric siloxane pendant groups was carried out with Grubbs 1st and 2nd generation, and Grubbs-Hoveyda ruthenium (Ru) catalysts. Monomer 1 gave high-molecular-weight polymers (M_n ca. 27?000-180?000) in high yields (80-100%). Monomers 2-5 also polymerized with Ru carbene catalysts to give high-molecular-weight polymers (M_n ca. 34?000-240?000) in high yields (66-100%). The onset temperatures of weight loss (T₀) of the polymers were 180-250 °C. The glass transition temperatures (T_gs) of poly(1) and poly(2) bearing branched siloxane linkages were near or higher than room temperature (27 and 101 °C). Meanwhile, the T_gs of poly(3)-poly(5) bearing linear siloxane linkages were much lower (−115 to −23 °C), and decreased with increasing length of the siloxane linkages. Poly(1) and poly(2) were hydrogenated completely, which was confirmed by ¹H NMR spectroscopy. The free-standing membranes of poly(1) and poly(2) showed high gas permeability; especially poly(2) is the most permeable to various gases among ROMP-polynorbornene derivatives reported so far.     

Synthesis and properties of helical polyacetylenes containing carbazole

Novel acetylene monomers containing carbazole with chiral menthyl and bornyl groups, 9-(1R,2S,5R)-menthyloxycarbonyl-2-ethynylcarbazole (1), 9-(1S,2R,5S)-menthyloxycarbonyl-2-ethynylcarbazole (2), 9-(1R,2S,5R)-menthyloxycarbonyl-3-ethynylcarbazole (3) and 9-(1S)-bornyloxycarbonyl-2-ethynylcarbazole (4) were synthesized and polymerized with a Rh catalyst to give the corresponding polymers [poly(1)-poly(4)] with moderate M_n value of (11.5-92.2) × 10³ in good yields (77-89%). CD spectroscopic studies revealed that poly(1), poly(2) and poly(4) took predominantly one-handed helical structure in CHCl₃, THF, toluene, and CH₂Cl₂, while poly(3) did not. Addition of methanol to CHCl₃ solutions of poly(1) and poly(2) resulted in the formation of aggregates showing smaller CD signals at 275 and 320 nm. The helical structure of poly(1) and poly(2) was very stable against heating. The polymers emitted fluorescence in 0.40-2.90% quantum yields. Poly(4) exhibited an obvious oxidation peak at 1.10 V. The polymers were thermally stable below 300 °C.     

Synthesis and characterization of chiral polythiophenes: Poly [(R)-(−) and (S)-(+)-2-(3′-thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate]

(R)-(−) (1) and (S)-(+)-2-(3′-Thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate (2) monomers were synthesized, characterized, and polymerized in chloroform using FeCl₃ as an oxidizing agent. Molecular weights of 2.6 × 10⁴ and 3.2 × 10⁴ for poly1 and poly2, respectively, were determined by SEC analysis. FTIR spectra of the polymers indicated the coupling of monomers through the α positions. UV-vis spectra showed absorption bands at λ_max = 226 and 423 nm for poly1 and poly2, ascribed to transitions of side groups and polythiophene backbone, respectively. Poly1 and poly2 remained stable up to 210 °C. At higher temperatures, a two step weight loss degradation process was observed for both polymers by TGA analysis. ¹H NMR, in the presence of Eu(tfc)₃, and optical rotation measurements indicate the chiral properties of the monomers 1 ([α]_D²⁸ = −76.2) and 2 ([α]_D²⁸ = +76.0), and the maintenance of chirality after polymerization (poly1 [α]_D²⁸ = −29.0 and poly2 [α]_D²⁸ = +28.4, c = 2.5 in THF). According to scanning electron microscopic analysis, the polymers are highly porous.     

Synthesis of poly(1-β-naphthyl-2-phenylacetylene) membranes through desilylation and their properties

The polymerization of 1-β-naphthyl-2-[(p-trimethylsilyl)phenyl]acetylene (8a) with TaCl₅-n-Bu₄Sn in cyclohexane provided a high molecular weight polymer (9a) (M_w=3.4×10⁶). The corresponding monomers having p-dimethyl-t-butylsilyl and p-dimethyl(10-pinanyl)silyl groups in place of p-trimethylsilyl group in 8a also polymerized in a similar way to give high molecular weight polymers (9b, 9c, respectively; M_w>1×10⁶). All these polymers were soluble in many common solvents such as toluene and chloroform, and provided free-standing membranes by casting from toluene solution. The oxygen permeability coefficients (P_O2) of 9a at 25 °C was as high as 3500 barrers. The membrane of poly(1-β-naphthyl-2-phenylacetylene) (10a) was prepared by desilylation of the membrane of 9a with trifluoroacetic acid. Polymer 10a was insoluble in any solvents, and showed high thermal stability (the onset temperature of weight loss in air ∼470 °C). The P_O2 value of 10a reached 4300 barrers. Not only the membrane of 9c but also its desilylation product 10c exhibited large optical rotations ([α]_D=+2924 and +9800°, respectively) and strong CD signals. This indicates that the membrane of 10c maintains the helical main chain conformation of 9c with a large excess one-handed helix sense.     

Synthesis and properties of polyacetylenes carrying N-phenylcarbazole and triphenylamine moieties

Novel acetylene monomers containing N-phenyl-substituted carbazole (Cz) and triphenylamine (TPA) groups, namely, 3-ethynyl-9-phenylcarbazole (1) and p-(N,N-diphenylamino)phenylacetylene (2) were synthesized, and polymerized with several Rh-, W-, and Mo-based catalysts. Poly(1) and poly(2) with high number-average molecular weights (15?500-974?000) were obtained in good yields (77-97%), when [(nbd)RhCl]₂-Et₃N (nbd = norbornadiene) was used as a catalyst. The polymers exhibited UV-vis absorption peaks derived from the Cz and TPA moieties at 250-350 nm and polyacetylene backbone above 350 nm. The UV-vis absorption band edge wavelengths of the polymers were longer than those of the corresponding monomers. Poly(2) exhibited a UV-vis absorption peak at a longer wavelength than poly(1) did, which indicates that poly(2) has main chain conjugation longer than that of poly(1). The molecular weights and photoluminescence quantum yields of the polymers obtained by the polymerization using [(nbd)RhCl]₂-Et₃N were larger than those of the Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃]-based counterparts. The cyclic voltammograms of the polymers indicated that they had clear electrochemical properties; the onset oxidation voltage of poly(1) was higher than those of N-alkyl-substituted Cz derivatives. The polymers showed electrochromism and changed the color from pale yellow to blue by application of voltage, presumably caused by the formation of charged polaron at the Cz and TPA moieties. The temperatures for 5% weight loss of the polymers were around 350-420 °C under air, indicating the high thermal stability.     

Synthesis and electro-optical properties of helical polyacetylenes carrying carbazole and triphenylamine moieties

Novel chiral acetylene monomers bearing carbazole and triphenylamine groups, namely, (S)-3-butyn-2-yl 2-(9-carbazolyl)ethyl carbonate (1) and (S)-3-butyn-2-yl 4-(diphenylamino)benzoate (2) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] catalyst to give the corresponding polymers with moderate molecular weights (M_n 13.0 × 10³ and 15.5 × 10³) in good yields (86% and 88%). CD spectroscopic studies revealed that poly(1) and poly(2) took predominantly one-handed helical structure in CHCl₃. The helical structures of poly(1) and poly(2) were very stable against heating and addition of MeOH. The solution of poly(1) and poly(2) emitted fluorescence in 0.52% and 7.2% quantum yields, which were lower than those of the corresponding monomers 1 and 2 (22.5% and 76.5%). The cyclic voltammograms of the polymers indicated that the oxidation potentials of the polymers were lower than those of the monomers. The polymers showed electrochromism and changed the color from pale yellow to pale blue by application of voltage, presumably caused by the formation of polaron at the carbazole and triphenylamine moieties. The onset temperatures of weight loss of poly(1) and poly(2) were 225 and 270 °C under air.     

Synthesis, characterization, and high gas permeability of poly(diarylacetylene)s having fluorenyl groups

Diarylacetylenes having fluorenyl groups and other substituents (trimethylsilyl, t-butyl, bromine, fluorine) (1a-1) were polymerized with TaCl₅-n-Bu₄Sn. Monomers 1a-l produced high molecular weight polymers 2a-l (M_w 5.1 × 10⁵-1.3 × 10⁶) in 12-59% yields. All of the polymers were soluble in common organic solvents, and gave tough free-standing membranes by the solution casting method. The onset temperatures of weight loss of polymers 2a-l in air were over 400 °C, indicating considerably high thermal stability. All the polymer membranes showed high gas permeability; e.g., the oxygen permeability coefficient (PO₂) of 2a was as large as 4800 barrers. Membrane 2d possessing two fluorine atoms at meta and para positions of the phenyl ring showed the highest oxygen permeability (PO₂ = 6600 barrers) among the present polymers.     

Preparation of π-conjugated polymers consisting of 2-decylbenzimidazole and thiophene units and chemical properties of the polymers

Polycondensation by Stille coupling of 2-decyl-4,7-dibromobenzimidazoles and N-methyl-2-decyl-4,7-dibromobenzimidazole with 2,5-bis(trimethylstannyl)thiophene and 5,5′-bis(trimethylstannyl)-2,2′-bithiophene gave the corresponding π-conjugated polymers, poly(2-decylbenzimidazole-4,7-diyl-thiophene-2,5-diyl) 1b, poly(2-decylbenzimidazole-4,7-diyl-bithiophene-2,5-diyl) 1c and poly(N-methyl-2-decylbenzimidazole-4,7-diyl-thiophene-2,5-diyl) 2b, in 98-99% yields. The polymers 1b and 2b were fully soluble in CF₃COOH, and partially soluble in DMF (about 60 and 40% for 1b and 2b, respectively) and NMP (about 70 and 40%, respectively). The NMP soluble part of 1b and DMF soluble part of 2b gave values of 0.36 and 0.24 dl g⁻¹ in NMP and DMF, respectively. The DMF soluble part of 1b, 1c and 2b showed absorption peaks at about 458, 465 and 388 nm, respectively, in DMF. In an alkaline medium the absorption peaks of 1b and 1c are shifted to a longer wavelength by 92-101 nm; the observed shifts in the acidic medium and alkaline medium were much larger than those observed with usual benzimidazoles with low molecular weights. Packing structures of 1b, 1c and 2b are discussed based on their XRD patterns.     

Novel poly(diphenylacetylene)s with both alkyl and silyl groups as gas permeable membranes: Synthesis, desilylation, and gas permeability

Diphenylacetylenes having a dimethyloctylsilyl group and an alkyl group at para positions [Me₂n-C₈H₁₇SiC₆H₄CCC₆H₄R; R = H (1a), i-Pr (1b), t-Bu (1c), n-Bu (1d)] and having only an alkyl group [PhCCC₆H₄R; R = i-Pr (1B), t-Bu (1C)] were synthesized and then polymerized with TaCl₅/n-Bu₄Sn catalyst to provide the corresponding poly(diphenylacetylene)s (2a, 2b, 2c, 2d, 2B, and 2C). The formed polymers afforded tough free-standing membranes by casting from toluene solutions. Desilylation reaction of Si-containing membranes (2a-d) was carried out with trifluoroacetic acid to give the desilylated membranes (3a-d). The permeability of these membranes to O₂, N₂, and CO₂ were determined. All the Si-containing membranes exhibited almost the same gas permeability. The desilylation of Si-containing membranes of 2a-c resulted in large increase of gas permeability. No apparent increasing of gas permeability was observed in the desilylation of 2d. To clarify the effects of desilylation, CO₂ diffusivity (D(CO₂)), CO₂ solubility (S(CO₂)), and fractional free volume (FFV) of the polymer membranes were investigated. The S(CO₂) values of desilylated membranes were much larger than that of Si-containing counterparts. The D(CO₂) and FFV of membranes of 2a-c increased through desilylation. The desilylated membrane of 3d had small D(CO₂) value and almost the same FFV compared with 2d. Further, the comparison of the permeability between three types of membranes with the same chemical structure revealed that the microvoids were not generated by the desilylation of membranes of poly(diphenylacetylene)s containing alkyl groups.     

Pd-catalyzed hydrosilylation polymerization of a dihydrosilane with diyne/triyne mixed systems affording crosslinked silylene-divinylene polymers and their properties

Treatment of a dihydrosilane (methylphenylsilane, 1) with mixtures of a diyne (p- or m-diethynylbenzene, 2a or 2b) and a triyne (1,3,5-triethynylbenzene, 3a or B,B′,B″-triethynyl-N,N′,N″-trimethylborazine, 3b; 1:2:3=100:95:5, 100:90:10, 100:80:20) in the presence of Pd-PCy₃ (Cy=cyclohexyl) catalyst gave new crosslinked silylenedivinylene polycarbosilanes. In TGA the resulting crosslinked polymers tended to show higher Td₅ values and higher char yields than the corresponding linear polymers. On the other hand, UV/vis absorption spectra of the crosslinked polymers obtained in the reactions of 2a or 2b with 3a exhibited increased broad peaks around 390 nm for 2a or 360 nm for 2b. Coincidently, their fluorescence spectra showed significant increase of the emission peaks in 400-550 nm. The crosslinked polymer derived from 2a and 3b, however, showed decrease of the absorption peak around 390 nm and profound depression of fluorescence peaks in 400-550 nm.     

Synthesis and gas permeation properties of various Si-containing poly(diarylacetylene)s and their desilylated membranes

Diarylacetylene monomers having trimethylsilyl groups and other substituents (substituted biphenyl, 1a and 1b; trimethylsilylmethylphenyl, 1c-e) were synthesized and polymerized with TaCl₅-n-Bu₄Sn catalyst to produce the corresponding poly(diarylacetylene)s (2a-d). Polymers 2a-c had high molecular weights and were soluble in common organic solvents. Free-standing membranes of 2a-c as well as previously reported 2f-h were prepared by the solution-casting method. Desilylation of these Si-containing polymer membranes was carried out with trifluoroacetic acid to afford 3a, 3b, and 3f-h. Upon desilylation, biphenyl-containing membranes became less permeable (3a, b), whereas fluorene-containing membranes became more permeable (3f-h). In particular, 3h exhibited extremely high gas permeability (PO₂ = 9800 barrers), which is about the same as that of poly(1-trimethylsilyl-1-propyne). Desilylated membranes 3a and 3f-h showed different gas permeability from that of polymers 2i-k which have the identical chemical structures and obtained directly by the polymerization of the corresponding monomers.     

Preparation and properties of polytolan membranes bearing p-hydroxyl groups

The polymerization of a novel monomer p-(t-butyldimethylsiloxy)tolan (1) with TaCl₅-n-Bu₄Sn provided a high molecular weight polymer (poly(1)), whose M_w reached 4.0×10⁶. The poly(1) membrane was prepared by the casting method, and converted into poly[(p-hydroxy)tolan] (poly(2)) with a mixture of trifluoroacetic acid/water. Whereas poly(1) dissolved in low polarity solvents such as toluene and chloroform, poly(2) was practically insoluble in any solvents, although it partly dissolved in methanol and ethanol. The onset weight loss temperatures of poly(1) and poly(2) in air were 320 and 360 °C, respectively, indicating fair thermal stability among substituted polyacetylenes. The oxygen permeability coefficients (P_O2) of poly(1) was 150 barrers, which is relatively small among polytolan derivatives, while that of poly(2) was 8.0 barrers and smaller owing to the presence of polar hydroxyl groups.     

Poly(7-oxanorbornenes) carrying 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO) radicals: Synthesis and charge/discharge properties

TEMPO-containing 7-oxanorbornene monomers 1-4 (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxy) were synthesized and polymerized via ring-opening metathesis using a ruthenium carbene catalyst. Monomers 1 and 3 gave polymers with number-average weights of 80?100 and 112?200 in 85 and 96% yields, respectively, whereas monomers 2 and 4 did not provide high molecular weight polymers. Poly(1) and poly(3) were soluble in common solvents including CHCl₃, CH₂Cl₂ and THF, while insoluble in hexane, diethyl ether and MeOH. They were thermally stable up to ca. 240 °C according to the TGA measurements in air. The secondary batteries utilizing the present polymers as cathode-active material demonstrated reversible charge/discharge processes, whose discharge capacities were 107 and 92.8 A h/kg, and displayed excellent high-rate charge and discharge properties. These cells demonstrated excellent cycle life, e.g., the discharge capacities of poly(1) and poly(3) showed less than 10% decrements even after 100 cycles.     

Syndiotactically enriched 1,2-selective polymerization of 1,3-butadiene initiated by iron catalysts based on a new class of donors

A series of phosphoryl (PO) contained compounds: triethylphosphate (a), diethylphenylphosphate (b), ethyldiphenylphosphate (c) triarylphosphates (d and h-m), triphenylphosphine oxide (e), phenyl diphenylphosphinate (f) and diphenyl phenylphosphonate (g) have been prepared. Iron catalysts, which are generated in situ by mixing the compounds with Fe(2-EHA)₃ and AlⁱBu₃ in hexane, are tested for butadiene polymerization at 50 °C. Phosphates donated catalysts have been, unprecedently, found to conduct extremely high syndiotactically (pentad, rrrr = 46.1-94.5%) enriched 1,2-selective (1,2-structure content = 56.2-94.3%) polymerization of butadiene. Introduction of electron withdrawing substituents on phenyl rings oftriphenylphosphate (k-m) remarkably promotes catalytic activity, while bulky substituent isopropyl at 2-position (h) has beneficial influence on regioselectivity. Employment of e, f or g as donor, results in a suppressed monomer conversion, accompanied by deteriorated 1,2-regioselectivity. The effects of polymerization conditions such as reaction temperature, types of cocatalysts and polymerization medium are also investigated by using catalyst system with tri(2,4-difluorophenyl)phosphate (m) as donor. Highly tolerance to polymerization temperature up to 80 °C is observed for the first time in the iron-based catalyst.     

Molecular architecture effect on reactivity of polynorbornenes with pendant α,β-unsaturated amide or ester bridged chains via ring-opening metathesis polymerization

The molecular architecture effect on active structure of miscellaneous polynorbornenes (Scheme 1) was investigated with pendant α,β-unsaturated amide or ester groups via ring-opening metathesis polymerization (ROMP). Remarkable differences in the reactivity and polymerization behavior of active norbornenes depend on various molecular architectures. Polynorbornenes derived from active norbornenes with ethylene between urethane group and ester group such as 3a,b (Scheme 1) showed excellent solubility. Organo-insoluble precipitate was obtained after ROMP of 5c with the amide group. Random copolymerization technique of bicyclo[2.2.1]hept-2-ene (NB) and 5c with amide group was considered to be a strategy to overcome the formation of precipitates, which expected to decrease the hydrogen bonding between two amide groups. High performance polynorbornenes with active groups could be designed with high potential of application for photoresist, UV curing and elastomers. Functional poly(5b) was incorporated into poly(methyl methacylate) [poly(MMA)] to produce AB cross-linked materials. The AB cross-linked material [15 wt% poly(5b), T_d10=355 °C in nitrogen] had higher thermal stability than pure poly(MMA) (T_d10=250 °C in nitrogen).     

Syntheses of well-defined poly(siloxane)-b-poly(styrene) and poly(norbornene)-b-poly(styrene) block copolymers using functional alkoxyamines

Functional alkoxyamines, 1-[4-(4-lithiobutoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (2) and 1-[4-(2-vinyloxyethoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (3) were prepared, and well-defined poly(hexamethylcyclotrisiloxane)-b-poly(styrene)[poly(D₃)-b-poly(St)] and poly(norbornene)-b-poly(St) [poly(NBE)-b-poly(St)] were prepared using the alkoxyamines. The first step was preparation of poly(D₃) and poly(NBE) macroinitiators, which were obtained by the ring-opening anionic polymerization of D₃ using 2 as an initiator and the ring-opening metathesis polymerization of NBE using 3 as a chain transfer. The radical polymerization of St by the poly(D₃) and poly(NBE) macroinitiators proceeded in the ‘living’ fashion to give well-defined poly(D₃)-b-poly(St) and poly(NBE)-b-poly(St) block copolymers.     

Synthesis of amphiphilic triblock copolymer of polystyrene and poly(4-vinylbenzyl glucoside) via TEMPO-mediated living radical polymerization

4-Vinylbenzyl glucoside peracetate 1 was polymerized with α,α′-bis(2′,2′,6′,6′-tetramethyl-1′-piperidinyloxy)-1,4-diethylbenzene 2 in chlorobenzene using (1S)-(+)-10-camphorsulfonic acid anhydrous (CSA) as an accelerator ([1]=0.4 M,[1]/[2]/[CSA]=75/1/1.3) at 125 °C for 5 h. The polymerization afforded poly(4-vinylbenzyl glucoside peracetate) having TEMPO moieties on both sides of the chain ends, 3, with a molecular weight (M_w,SLS) of 8500, a polydispersity index (M_w/M_n) of 1.09, and an average degree of polymerization of the 1 unit (x) of 17. Styrene (St) was polymerized with 3 in chlorobenzene at 125 °C (St/chlorobenzene=1/2, w/w). The polymerization successfully afforded polystyrene-poly(4-vinyl glucoside peracetate)-polystyrene, 4, when the polymerization time was below about 2 h. Polymer 4 with the M_w,SLS of 12,500, 17,900, and 29,400, the compositions (y-x-y) of 20-17-20, 45-17-45, and 100-17-100, and the M_w/M_n of 1.12, 1.14 and 1.17 were modified by deacetylation using sodium methoxide in dry-THF into polystyrene-poly(4-vinyl glucoside peracetate)-polystyrene, 5. The solubility of polymer 5 was examined using a good solvent for polystyrene such as toluene and for the saccharide such as H₂O.     

Living radical polymerization of styrene mediated by a piperidinyl-N-oxyl radical having very bulky substituents

A new cyclic nitroxide 1 and the corresponding alkoxyamines 9 and 10 were synthesized and the polymerization of styrene (St) initiated with 10 was investigated. The NO-C bond of 9 is very weak, cleaving at room temperature. On the other hand, alkoxyamine 10 is stable at room temperature and the A_act and E_act for the NO-C bond homolysis were determined to be 1.4 × 10¹⁵ s⁻¹ and 124.5 kJ mol⁻¹, respectively. When the polymerization of St was carried out at 70 °C, the resultant poly(St) showed narrow polydispersities below 1.25. In the polymerization at 90 °C, the resulting poly(St) showed narrow polydispersity until 60% conversion, but M_w/M_n was rapidly increased above 60% conversion. On the other hand, the polymerization at 120 °C gave poly(St) with broad polydispersities. The unusual polymerization behavior was discussed on the basis of the SEC and ESR results.     

Tyrosine-based poly(m-phenyleneethynylene-p-phenyleneethynylene)s. Helix folding and responsiveness to a base

The Sonogashira-Hagihara polymerization of 3′,5′-diiodo-N-α-tert-butoxycarbonyl-l-tyrosine methyl ester (1) and 3′,5′-diiodo-N-α-tert-butoxycarbonyl-O-methyl-l-tyrosine methyl ester (2) with para-diethynylbenzene (3) was carried out to obtain optically active poly(m-phenyleneethynylene-p-phenyleneethynylene)s [poly(1) and poly(2)] with M_n’s ranging from 9900 to 15,000 in 80-87% yields. Poly(1) exhibited intense CD signals in DMSO and THF, but did not in CH₂Cl₂, indicating that it took a predominantly one-handed helical conformation in the former two solvents. On the other hand, there was no evidence for poly(2) to take a helical structure in these solvents. Poly(1) turned the CD sign at 390 nm from plus to minus in DMSO/H₂O = 9/1 (v/v) by the addition of NaOH. Alkaline hydrolysis of ester moieties of poly(1) and poly(2) gave the corresponding polymers having carboxy groups [poly(1a) and poly(2a)]. Poly(1a) and poly(2a) increased the CD intensity by the addition of NaOH.     

Synthesis and characterization of side-chain liquid crystalline homopolymers and block copolymers containing biphenyl-4-ylthiophene and biphenyl-4-ylfluorene pendants

A series of new liquid crystalline homopolymers (P1 and P2) and block copolymers (P3 and P4) composed of methacrylates containing pendant biphenyl-4-ylthiophene (M1) and biphenyl-4-ylfluorene (M2) units were synthesized by atom transfer radical polymerization (ATRP). The number-average molecular weights (M_n) of the homopolymer (P2) and diblock copolymers (P3 and P4) were in the range of 5153-8713 g mol⁻¹ with polydispersity indices (PDIs) between 1.17 and 1.25. The thermal, mesogenic, and photoluminescence (PL) properties of all polymers were investigated. Except for the absence of mesogenic properties in block copolymer P4, polymers P1 and P3 possessed the smectic A phase and polymer P2 exhibited the nematic phase. Moreover, the mesomorphism and the layer d-spacing values of the smectic A phase in polymers P1 and P3 were confirmed and characterized by X-ray diffraction (XRD) patterns.