Glass transition temperature modification of acrylic and dienic type copolymers of 4-chloromethyl styrene with incorporation of (Me3Si)3C- groups

The new functional styrenic monomer, 4-trisylmethyl styrene (TsiMS) [Tsi=trisyl=tris(trimethylsilyl)methyl], was synthesized by reacting 4-chloromethyl styrene (CMS) with trisyllithium (TsiLi) in tetrahydrofuran (THF) solvent in the presence of copper chloride (CuCl). Attempt for the free radical polymerization of TsiMS by α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator at 70 ± 1 °C failed for several periods of times. This result showed that the trisyl group is a highly sterically hindered substituent and, subsequently, TsiMS becomes resistant for polymerization. Therefore, for preparation of new methacrylic, acrylic and dienic copolymers of TsiMS, we firstly synthesized the copolymers of CMS with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA) and isoprene (IP) by free radical polymerization method in toluene solution at 70 ± 1 °C using AIBN initiator to give the copolymers I-VI in good yields. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). The trisyl groups were then covalently attached to the obtained copolymers as side chains by reaction between excess of TsiLi and benzyl chloride bonds of CMS units, to give the copolymers - in 80-92% yields. All the resulted polymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility of all the copolymers was examined in various polar and non-polar solvents. The glass transition temperature (T_g) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. The T_g value of copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in polymer side chains, create new macromolecules with novel modified properties.     

Synthesis, characterization and biocompatibility studies of oligosiloxane modified polythiophenes

This paper describes the preparation and characterization of homopolymers of 3-oligo(dimethylsiloxane)thiophene macromonomers, V-VIII, and copolymers with 3-methylthiophene. The thiophene macromonomers were prepared by hydrosilylation reaction between ω-(Si-H)-oligo(dimethylsiloxane), I-IV, and 3-propenylthiophene using a platinum-divinyltetramethyldisiloxane complex as the catalyst. The products were characterized by ¹H, ¹³C, ²⁹Si NMR and IR spectroscopy; DSC (differential scanning calorimetry) and GPC studies. Two distinct glass transition temperatures are observed for poly[VIII], a T_g at −79 °C corresponds to the soft oligo(dimethylsiloxane) phase and the T_g at 190 °C corresponds to the hard thiophene backbone. Homopolymers of V and VI, and copolymers may be doped with I₂ to generate electronic conductive material, a copolymer of poly[V]-co-poly[3-methylthiophene] (50/50, w/w) has an electronic conductivity value of 5 × 10⁻⁵ S/cm at 25 °C. The polymers are tractable and may be molded into thin films; a number of the polymers are soluble in organic solvents. Polythiophene modified with oligosilioxanes are biocompatibile; the polymers minimally interfere with the growth of HeLa cells.     

Cyclopolymerization XXXIII. Radical polymerizations and copolymerizations of 1,6-dienes with 2-phenylallyl group and thermal properties of polymers derived therefrom

Radical polymerizations of α-allyloxymethylstyrene (1) and copolymerizations of α-(2-phenylallyloxy)methylstyrene (2) were undertaken to acquire comprehensive understanding on polymerization behavior of these dienes and to get polymers with high thermal stability and high glass transition temperature (T_g). One of the monofunctional counterparts of 1 is a derivative of α-methylstyrene, the ceiling temperature of which is low, and the other is an allyl compound that is well-known for the low homopolymerization tendency. This means that the intermolecular propagation reactions leading to pendant uncyclized units are suppressed during the polymerization of 1 to yield highly cyclized polymers. In fact, the degree of cyclization of poly(1) obtained at 140 °C attained the value 92%. Structural studies revealed that repeat cyclic units of poly(1) consist exclusively of five-membered rings. Poly(1) was found to be stable up to 300 °C, but its T_g values were detected at around 100 °C. They are considerably lower than the targeted values which should lie between 180 and 220 °C. An additional drawback of poly(1) is its low molecular weight probably due to a degradative chain transfer. For this reason, copolymerizations of 2 with 1 and with styrene were also carried out to seek for the possibility to control the thermal properties precisely. Monomer 2 was chosen, since it has been reported in our previous work that it yields polymers with thermal stability up to 300 °C and T_g higher than 250 °C. Copolymerization of 2 with styrene afforded polymers with desired thermal properties and high molecular weight.     

Novel organosoluble and colorless poly(ether imide)s based on 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride and trifluoromethyl-substituted aromatic bis(ether amine)s

A series of novel fluorinated poly(ether imide)s (IV) having inherent viscosities of 0.70-1.08 dL/g were prepared from 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride (I) and various trifluoromethyl (CF₃)-substituted aromatic bis(ether amine)s II_a-g by a standard two-step process with thermal and chemical imidization of poly(amic acid) precursors. These poly(ether imide)s showed excellent solubility in many organic solvents and could be solution-cast into transparent, flexible, and tough films. These films were essentially colorless, with an ultraviolet-visible absorption edge of 375-380 nm and a very low b^∗ value (a yellowness index) of 5.5-7.3. They also showed good thermal stability with glass-transition temperatures of 207-269 °C, 10% weight loss temperatures in excess of 474 °C, and char yields at 800 °C in nitrogen more than 62%. In comparison with analogous V series poly(ether imide)s without the -CF₃ substituents, the IV series polymers showed better solubility, lower color intensity, and lower dielectric constants.     

Synthesis and characterization of new soluble and thermally stable poly(ester-imide)s derived from N-[3,5-bis(N-trimellitoyl)phenyl]phthalimide and various bisphenols

A new dicarboxylic acid chloride (2) bearing three preformed imide rings was synthesized by treating N-(3,5-diaminophenyl)phthalimide with trimellitic anhydride followed by refluxing with thionyl chloride. A novel family of aromatic poly(ester-imide)s with inherent viscosities of 0.27-0.35 dl g⁻¹ were prepared from 2 with various bisphenols such as resorcinol (3a), hydroquinone (3b), 2,2′-dihydroxybiphenyl (3c), 4,4′-dihydroxybiphenyl (3d), bisphenol-A (3e), 2,2′-dimethyl-4,4′-dihydroxybiphenyl (3f), 1,5-dihydroxynaphthalene (3g), 2,7-dihydroxynaphthalene (3h), and 2,2′-dihydroxy-1,1′-binaphthyl (3i) by high-temperature solution polycondensation in nitrobenzene using pyridine as hydrogen chloride quencher. All of the resulted polymers were fully characterized by FT-IR and NMR spectroscopy and elemental analyses. The poly(ester-imide)s exhibited excellent solubility in some polar organic solvents. From differential scanning calorimetry, the polymers showed glass-transition temperatures between 259 and 353 °C. Thermal behaviors of the obtained polymers were characterized by thermogravimetric analysis and the 10% weight loss temperatures of the poly(ester-imide)s were found to be in the range between 451 and 482 °C in nitrogen. Furthermore, crystallinity of the polymers was estimated by means of wide-angle X-ray diffraction.     

Thermal stability and high glass transition temperature of 4-chloromethyl styrene polymers bearing carbazolyl moieties

A new styrene derivative monomer, 4-(N-carbazolyl)methyl styrene (CzMS), was synthesized by reacting 4-chloromethyl styrene with carbazole in the presence of sodium hydride. Then, CzMS was homopolymerized and copolymerized with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA) and n-butyl acrylate (BA) by free radical polymerization method in N,N-di-methylformamide (DMF) solution at 70 ± 1 °C using azobisisobutyronitrile initiator to give the copolymers I-V in good yields. The structure of all the resulted polymers was characterized and confirmed by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The average molecular weight and glass transition temperature of polymers were determined using gel permeation chromatograph (GPC) and differential scanning calorimeter (DSC) instruments, respectively. It was found that these polymers with carbazole moieties have high thermal stability and the presence of bulk carbazole groups in polymer side chains leads to an increase in the rigidity and glass transition temperature of polymers.     

Synthesis, X-ray structures, and syndiospecific polymerization behavior of styrene of new (pentamethylcyclopentadientyl) titanatranes containing modified tetradentate triethanolamine ligands

A series of monomeric pentamethylcyclopentadienyltitanatranes, [n = 0, 1; n = 1, 2; n = 2, 3], were synthesized by the reaction of Cp∗TiCl₃ with corresponding triethanolamines such as (HOCH₂CH₂)_nN(CH₂CMe₂OH)_{3 − n} (n = 0, L1H₃; n = 1, L2H₃; n = 2, L3H₃), which varied by the number of CMe₂ groups adjacent to an OH functionality from 3 (L1H₃) to 2 (L2H₃) to 1 (L3H₃), in the presence of NEt₃. All complexes were characterized by elemental analysis and solution ¹H and ¹³C{¹H} NMR spectroscopy. Moreover, their solid state structures, which are slightly distorted three-legged piano stool geometry, have been confirmed by single crystal X-ray diffraction analysis. On activation with methylaluminoxane (MAO), these complexes showed good catalytic activity for the polymerization of styrene producing syndiotactic polystyrene (SPS) with high molecular weights. Compounds 1 and 2 bearing more than two pairs of methyl substituents on the side arms of triethanolamines showed the enhanced catalytic activities as the polymerization temperature went up from 50 °C to 110 °C, whereas less bulky complexes 3 and Cp∗Ti(OCH₂CH₂)₃N (4) gave the decreased activities as polymerization temperature rose. Unlike 3 and 4, complexes 1 and 2 in the presence of MAO as a cocatalyst gave SPS with controlled bimodal molecular weight distribution. Bimodal properties were much distinct at low polymerization temperature.     

Polymerization of methyl methacrylate in the presence of iron(II) complex with tetradentate nitrogen ligands under conditions of atom transfer radical polymerization

Four tetradentate nitrogen ligands, viz. dichloro{[N,N^′-diphenyl-N,N^′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (1), {[N,N^′-dioctyl-N,N^′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (2), {[N,N^′-dibenzyl-N,N^′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (3), and (1R,2R)-(−)-N,N^′-di(quinoline-2-methyl) di-iminocyclohexane (4), were investigated as novel complexing ligands in iron-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate where ethyl-2-bromoisobutyrate was the initiator in o-xylene at 90 °C. With ligands 1 and 2 the experimental molecular weights increased gradually with monomer conversion. High to moderate conversions (87%, 43%) were obtained in relatively short times (90 min for 1 and 30 min for 2), which indicates an efficient catalyst system, but after these times a dramatic increase in viscosity of the polymerization medium led to loss of control. It is noteworthy that polymerization proceeded in a controlled manner with ligand 1, which has two rather bulky substituents on the N-atom. Such bulky ligands did not work for a copper-based system, where they led to excessive terminations or other side reactions. When the bulkiness of the substituents was significantly increased, as in ligand 3, a decrease in polymerization rate and loss of control occurred. Ligand 4 was less efficient than the other ligands, probably because the ethylene bridge was replaced by cyclohexane bridge.     

Synthesis of 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional groups via Peterson protocol

Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional and reactive groups in a convenient one-pot operation via the Peterson protocol. Then poly(styrene) and poly(α-methylstyrene) (?&II) random homopolymers were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. The aldehyde group is introduced by direct electrophilic substitution of polymers ? and II. This formylation reaction was conducted in two different solvents: dichloromethane (CH₂Cl₂) and nitrobenzene (PhNO₂). The results indicate that PhNO₂ appeared to be a more suitable solvent for such an aldehyde functionalization of the polymers. The formylated polymers (I_CHO, II_CHO) were then converted to Si-H functionalized polymers (I_Si-H, II_Si-H) via reaction with tris(dimethylsilyl)methyllithium, (HMe₂Si)₃CLi.     

Preparation of syndiotactic polystyrene using the doubly bridged dinuclear titanocenes

As a new kind of dinuclear metallocene four DBDM (doubly bridged dinuclear metallocene) that hold two different bridging units linking two metallocenes have been prepared and their polymerization properties have been pursued. The selected bridging ligands for DBDM were polymethylene and dialkoxy terminated derivatives to bond two cyclopentadienyls and two titanium centers, respectively. The syntheses of new dinuclear metallocenes 5-8 were able to be achieved by the reaction between dinuclear half-titanocenes 1 and 2 and ditrimethylsiloxy terminated derivatives 3 and 4 at −78 °C. The EI mass spectra and ¹H and ¹³C NMR spectral data were very informative to identify their formulations as well as structural features. The polymerization of styrene was conducted by using DBDM 5-8. From the polymerization studies it was found that (i) DBDM 7 and 8 holding 2,2-diethyl-1,3-dipropanoxy (DEP) bridge not only show greater activity but also produce higher syndiotactic polystyrene than DBDM 5 and 6 holding 1,1,4,4-tetramethyl-1,4-dibutanoxy (TMB) bridge between two titanium centers, (ii) activities increase with increase in the polymerization temperature, the amount of cocatalyst and monomer concentration, (iii) the most crucial factor to control the stereoregularity of the resulting polystyrene is the styrene concentration in reaction system, (iv) surprisingly the catalyst structure does not have much effect on molecular weight of the obtained polystyrenes. The most significant feature from this study is that the second bridging dialkoxy terminated ligands connecting two titanium centers likely exert more pronounced influence than the polymethylene bridges between two Cp groups on the activity of the catalyst as well as the stereochemistry of the generated polymers.     

Synthesis and decarboxylation of N-acyl-α-triphenylphosphonio-α-amino acids: a new synthesis of α-(N-acylamino)alkyltriphenylphosphonium salts

4-Phosphoranylidene-5(4H)-oxazolones 1 undergo hydrolysis in THF in the presence of HBF₄ at room temperature to give N-acyl-α-triphenylphosphonioglycines 3 (R² = H) in very good yields. 4-Alkyl-4-triphenylphosphonio-5(4H)-oxazolones 2 react with water in CH₂Cl₂/THF solution without any acidic catalyst at 0-5 °C in a few days yielding N-acyl-α-triphenylphosphonio-α-amino acids 3 (R² = Me) or α-(N-acylamino)alkyltriphenylphosphonium salt 4 (R² = CH₂OMe). α-Triphenylphosphonio-α-amino acids 3, on heating up to 105-115 °C under reduced pressure (5 mmHg) or on treatment with diisopropylethylamine in CH₂Cl₂ at 20 °C undergo decarboxylation to give the corresponding α-(N-acylamino)alkyltriphenylphosphonium salts 4, usually in very good yields.     

Titanium isodicyclopentadienide hemimetallocenes for ethylene/styrene copolymerization

The syndiotactic polymerization of styrene with exo-[(η⁵-isodiCp)TiCl₃] 1/methylalumoxane (MAO; isodiCp=isodicyclopentadienyl) was studied as well as the ethylene/styrene copolymerization with exo-[{η⁵:η¹(N)-isodiCp(SiMe₂Nt-Bu)}TiCl₂] 2/MAO. These two catalytic systems are stable during polymerization. The half-sandwich titanocene 1 exhibits good syndiospecificity and average activity. The bridged half-sandwich amino complex 2 was found to incorporate styrene into polymer chains at 70 °C. Activity results decrease with increasing styrene concentrations.     

Zirconium complexes with versatile β-diketiminate ligands: Synthesis, structure, and ethylene polymerization

A series of zirconium complexes (2c, 2d, 2f, 2g, 2h, 2i) containing symmetrical or unsymmetrical β-diketiminate ligands were synthesized by the reaction of ZrCl₄ · 2THF with lithium salt of the corresponding ligand in 1:2 molar ratio. X-ray crystal structures reveal that complexes 2d and 2g adopt distorted octahedral geometry around the zirconium center. These complexes showed moderate activities for ethylene polymerization, when methylaluminoxane (MAO) was used as cocatalyst. The steric and electronic effects of the substituents at the phenyl rings had considerable influence on the catalytic activities of the metal complex, as well as the molecular weights and molecular weight distributions (MWD) of produced polymers. Introduction of electron-withdrawing CF₃ group to phenyls in the ligand led to a significant increase of catalytic activities, and complex 2f (p-CF₃) exhibited the highest catalytic activity of 7.45 × 10⁵ g PE/mol-Zr · h among the investigated complexes. Complexes 2a-d could produce ultra-high molecular weight polyethylenes (UHMWPE) that were hardly dissolvable in decahydronaphthalene or 1,2-dichlorobenzene under the molecular weight measurement conditions. Nevertheless, polyethylenes with broad MWD could be afforded by complexes 2g-i, which was probably due to the introduction of bulky unsymmetrical ligands leading to the formation of multi active species under polymerization conditions. High-temperature ¹³C NMR data indicate the linear structure of obtained polyethylenes.     

Synthesis and characterization of dithienobenzothiadiazole-based donor–acceptor conjugated polymers for organic solar cell applications

New donor–acceptor conjugated polymers (P1 and P2) containing a fused-ring dithienobenzothiadiazole (DT-BTD building block) were synthesized by using the Stille copolymerization method. The synthesized polymers were characterized by ¹H NMR, GPC, and elemental analysis. The optical band gaps of the polymers were found to be 1.86 and 1.9 eV, respectively, as calculated from their film onset absorption edge. Upon annealing both produced a distinct shoulder peak in their film absorption spectra. The electrochemical studies of P1 and P2 revealed that the HOMO and LUMO energy levels of the polymer were −5.3, −5.1 eV, and −3.4, −3.2 eV, respectively. The polymers are thermally stable up to 250–350 °C.     

Synthesis, characterization, and catalytic activities in syndiospecific polymerization of styrene for half-sandwich titanium complexes with non-Cp tridentate dianionic ligands MeN(CH2CR2O)2

New half-titanocenes, Cp^∗TiCl[(OCR₂CH₂)NMe(CH₂CR^′₂O)] [R,R′ = H (1), R,R′ = Me, H, (2), R,R′ = Me (3)], were prepared from Cp^∗TiCl₃ (4) with the corresponding alcohols in the presence of triethylamine. X-ray analysis shows that 1 has slightly distorted trigonal bipyramidal geometry around Ti. These complexes exhibited moderate catalytic activities for syndiospecific styrene polymerization in the presence of MAO and the activity increased in the order: 2 > 1 > 4 > 3 (at 50 °C), 1 > 2 > 4 > 3 (at 70 °C and 90 °C).     

Molecular design, synthesis and electro-optic properties of novel Y-type polyurethanes with high thermal stability of second harmonic generation

2,4-Di-2^′-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with 2,4-toluenediisocyanate and 3,3^′-dimethoxy-4,4^′-biphenylenediisocyanate to yield unprecedented novel Y-type polyurethanes (4-5) containing 2,4-dioxybenzylidenemalononitrile group as a nonlinear optical (NLO) chromophore, which constitutes a part of the polymer backbone. The resulting polyurethanes 4-5 were soluble in common organic solvents such as acetone and DMF. Polymers 4-5 showed a thermal stability up to 260 °C from thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC) giving T_g values around 143-156 °C. The approximate lengths of aligned NLO-chromophores estimated from AFM images of poled polymer films were about 10 nm. The SHG coefficients (d₃₃) of poled polymer films were around 7.4 × 10⁻⁹ esu. These Poled polymers exhibited a greater thermal stability of dipole alignment even at 10 °C higher than T_g, and no SHG decay was observed below 155 °C due to the partial main chain character of the polymer structure and extensive hydrogen bonds between urethane linkage, which is acceptable for NLO device applications.     

Synthesis and polymerization of a novel perfluorinated monomer

Perfluoro(5-methylene-2,2-dimethyl-1,3-dioxolane) (1) was synthesized by utilizing a direct fluorination reaction. Compound 1 was an entirely novel monomer with difluoromethylene at position 5 on the dioxolane ring as an unprecedented polymerization site. It successfully polymerized with tetrafluoroethylene to afford copolymers, which had T_g values in the range of 60-90 °C. The content of monomer 1 in the obtained polymers was less than 20 mol%, which seemed insufficient for giving various unique properties to polymers. However, each polymer was expected to be a superior material because of their advanced thermal stability. Comparison with copolymers of 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole and tetrafluoroethylene is also discussed.     

The reaction of α-phenethyl radicals with 1,4-benzoquinone and 2,6-di-tert-butyl-1,4-benzoquinone

The absolute rate constant for 1,4-benzoquinone (BQ) irreversibly trapping α-phenethyl radicals (3) has been determined as 4.4×10⁶ M⁻¹ s⁻¹ at 43 °C using acyclic cis azoalkane 9c as a radical precursor. These reactants afford the hydroquinone mono ether 4 at 30 °C but a mixture of products at elevated temperature. 2,6-Di-tert-butyl-1,4-benzoquinone (DTBQ) also reacts with 3 but the cyclohexadienone products are thermally labile.     

Synthesis of photochromic diarylethene polymers for a write-by-light/erase-by-heat recording system

A functionalized styrene monomer (1a) having a photochromic diarylethene chromophore with functional properties of photocoloration, photostability of the colored state, and thermal erasion by heating was synthesized, and the polymer and copolymers of 1a were prepared by radical polymerization and copolymerization. Their polymers exhibited excellent photocoloration and rapid thermal bleaching above 150 °C in solution and in the solid state as well as the performance of the monomeric diarylethene chromophore. In addition, the colored state has a high photostability under visible room light. The diarylethene homopolymer had a glass transition temperature (T_g) as high as polystyrene. The copolymer of 1a with N-1-adamantylmaleimide exhibited extremely high T_g above 200 °C with keeping the photofunctional performance. Such photochromic polymer and copolymers with high T_g can be potentially applied to rewritable display materials and image recordings by a write-by-light/erase-by-heat system.     

Synthesis and properties of soluble and light-colored poly(amide-imide-imide)s based on tetraimide-dicarboxylic acid (TIDA) and various aromatic diamines: TIDA from 4,4′-oxydiphthalic anhydride, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, and 3-aminobenzoic acid

A new tetraimide-dicarboxylic acid (TIDA) I was synthesized starting from 3-aminobenzoic acid (m-ABA), 4,4′-oxydiphthalic anhydride (ODPA), and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (BAFPB) at a 2:2:1 molar ratio in N-methyl-2-pyrrolidone (NMP). A series of organosoluble, light-colored poly(amide-imide-imide)s (PAII, III_a-j) was prepared by triphenyl phosphite-activated polycondensation from the tetraimide-diacid I with various aromatic diamines (II_a-j). All the polymers were readily soluble in a variety of organic solvents such as NMP, N,N-dimethyl acetamide (DMAc), dimethyl sulfoxide, and even in less polar m-cresol and pyridine. Polymer films cast from DMAc had the cutoff wavelengths between 374 and 384 nm and had the b^∗ values in the range of 14.8-30.2. Polymers III_a-j afforded tough, transparent, and flexible films, which had tensile strengths ranging from 87 to 103 MPa, elongations at break from 11% to 37%, and initial moduli from 1.9 to 2.3 GPa. The glass transition temperatures of these polymers were in the range of 242-274 °C. They had 10% weight loss temperature above 526 °C and showed the char yield more than 55% residue at 800 °C in nitrogen.