Synthesis of Optically Active Helical Poly(2-methoxystyrene). Enhancement of HeLa and Osteoblast Cell Growth on Optically Active Helical Poly(2-methoxystyrene) Surfaces

Poly(2-methoxystyrene)s (P2MS) were synthesized using n-BuLi in THF and toluene at various temperatures. At ?20°C and higher temperatures, toluene was an effective polymerization solvent for synthesizing poly(2-methoxystyrene). Under these conditions, polymers with good yields and reasonable molecular weight distributions were obtained. Polymers synthesized under all conditions were isotactic; the most highly isotactic polymer was obtained in toluene at ?20°C. The m (isotactic dyad) content of the polymers synthesized in toluene at 0°C and ?20°C was 0.65 and 0.74, respectively. Optically active helical (+) and (?) P2MS were synthesized by asymmetric polymerization utilizing (+) or (?) [2,3-dimethoxy1,4(dimethylamino)butane] (DDB)/tolyl lithium initiating complex in toluene. Asymmetric polymerizations were also carried out at 0°C to synthesize optically active polymers. The optical rotations of the polymers were found to be dynamic and reversible, strongly suggesting contribution of the chiral higher ordered structure to the overall optical rotation. Geometry optimization carried out using various force fields such as MM+, AMBER and CHARMM suggests that isotactic P2MS form low energy stable helical conformations. HeLa cells showed better growth on surfaces prepared using chiral polymers compared to the surfaces prepared with achiral polymers. Similarly, chiral P2MS surfaces were also more effective as supports for mouse and human osteoblast cells. The cell attachment and growth data demonstrate that chiral P2MS surfaces were better supports compared to achiral P2MS surfaces. Atomic force microscopy (AFM) studies on surfaces prepared using chiral poly(2-methoxystyrene) showed more discrete topography features compared to surfaces prepared with achiral polymers. Thus, the surface topography may play a role in determining polymer–cell interactions.     

Polymerization of bicyclic acetals, 8. Cationic polymerization of 6,8-dioxabicyclo[3.2.1]oct-2-ene

Poly(5,6-dihydro-2H-pyran-2,6-diyloxymethylene) ( 6 ), a new polyacetal having a dihydropyran ring in its repeating unit was prepared by selective ring-opening polymerization of 6,8-dioxabicyclo[3.2.1]oct-2-ene ( 5 ) at temperatures between ?60 and ?90°C in dilute methylene chloride or toluene solutions using boron trifluoride etherate as initiator. The resulting polymers, having a number average molecular weight up to 1,5 · 10⁴, melted at 110 – 130°C and decomposed at ≈ 170°C in air. The isotactic dyad content of the polymers, estimated by ¹³C NMR spectroscopy, was found to be in the range of 70 to 77 mole-%, somewhat lower than that of its saturated analogue, poly(tetrahydropyran-2,6-diyloxymethylene), ( 2 ). The preferred formation of the isotactic sequence along the polymer chain is rationalized in terms of the enantiomer selection by the growing chain end control mechanism as previously proposed for the polymerization of 6,8-dioxabicyclo[3.2.1]octane, ( 1 ).     

Modifizierung von homo- und copolymeren des epichlorhydrins durch polymeranaloge umsetzungen

Poly(epichlorohydrin) and poly(epichlorohydrin-co-ethylene oxide) were modified by reaction with potassium thiocyanate (KSCN), tetrabutylammonium p-toluenesulfinate (NBu₄SO₂C₇H₇) and tetrabutylammonium benzenesulfinate (NBu₄SO₂C₆H₅). Though the substitution of chlorine in the polymers with these nucleophilic reagents in most cases is accompanied by side reactions, appropriate reaction conditions allow degrees of substitution higher than 90% to be obtained. The glass transition temperature (T_g) of the thiocyanate-modified homo- and copolymer exhibits only a small increase with increasing degree of substitution. While the T_g of the original homo- and copolymer is observed at ?20°C and ?38°C, respectively, the glass transition of the highly substituted homopolymer occurs at ?12°C and for the copolymer at ?31°C. On the other hand, the thiocyanate-modified polymers show a remarkably higher decomposition temperature of about 250°C as compared with that of the unmodified polymers (160–180°C). In addition, the solubility is markedly influenced by the substitution. While the original homo- and copolymers are soluble in, e.g., benzene and toluene, the highly modified products are only soluble in polar solvents such as THF, acetone, DMSO and diglyme. Introducing sulfonyl groups, the resulting polymers exhibit a glass transition temperature increased to a greater extent. For the homopolymer with the highest degree of substitution (98,3%), a T_g of 73°C is observed. Concerning the decomposition temperature, a drastical increase up to 370°C occurs. Finally the influence of phase transfer catalysts on the described reactions was investigated.     

New poly(amide-imide) syntheses, 4 Poly(amide-imide)s derived from 2,5-bis(4-aminophenyl)-3,4-diphenylthiophene and various bis(trimellitimide)s

Fifteen bis(trimellitimide)s 2a–o were prepared by condensation of the corresponding aliphatic or aromatic diamines with trimellitic anhydride. A series of structurally new poly(amideimide)s were synthesized by the direct polycondensation of these bis(strimellitimide)s with 2,5-bis(4-aminophenyl)-3,4-diphenylthiophene using triphenyl phosphite and pyridine as condensing agents in N-methyl-2-pyrrolidone (NMP). The resultant poly(amide-imide)s have inherent viscosities in the range between 0,72 and 2,73 dL/g at 30°C in N,N-dimethylacetamide (cf. Tab. 2). The polymers are amorphous and readily soluble in polar aprotic solvents such as N,N-dimethylacetamide (DMAc) and NMP. Transparent and tough films can be cast from their solutions. Most aliphatic-aromatic poly(amide-imide)s show a glass transition in the range between 203 and 242°C in their differential scanning calorimetry (DSC) traces, whereas the wholly aromatic poly(amide-imide)s show no discernible transition before decomposition. The thermal stability of the polymers was evaluated by thermogravimetry which showed the 10% weight-loss temperatures in the range between 414 and 459°C in air and between 451 and 578°C in a nitrogen atmosphere for the aliphatic-aromatic poly(amide-imide)s and above 500°C in both air and nitrogen atmosphere for the wholly aromatic poly(amide-imide)s.     

Sequential reordering in condensation polymers, 5. Preparation and characterization of copolymers via transesterification of a polycaprolactonepoly(2,2-dimethyltrimethylene carbonate) blend

A blend of polycaprolactone (PCL) and poly(2,2-dimethyltrimethylene carbonate) (PDTC) containing catalytic amounts of dibutyltin dimethoxide was prepared from solution. The blend was then subjected to melt-mixing at 200°C and samples were taken after different times. According to thermal analysis data, with the increase of reaction time a gradual loss of the crystallizability of the blend components is observed, and after 70 min at 200°C the system becomes completely amorphous. ¹³C NMR data suggest that the loss of crystallizability of the blend is accompanied by an abrupt decrease in PCL and PDTC sequence lengths reaching after 70 min at 200°C an average length of about two repeating units each. These effects are explained by transesterification reactions between the lactone and carbonate units.     

Syntheses and properties of N-(1,3-diisocyanato-1-propyl)phthalimide and its polymers

N-(1,3-Diisocyanato-1-propyl)phthalimide ( 5 ) was synthesized as a new monomer from glutamic acid ( 1 ) through N-phthaloylglutamic acid ( 2 ), N-phthaloylglutamoyl dichloride ( 3 ) and N-phthaloylglutamoyl diazide ( 4 ), followed by a Curtius rearrangement. In the Curtius rearrangement, the carbonylazido group with the phthalimido group in 4-position decomposes at 25°C, whereas the other carbonylazido group with the phthalimido group in 2-position is stable up to 45°C. The monomer is a viscous and transparent liquid which can be purified by molecular distillation without racemization. A series of polymers, including polyureas ( 13a–i ), polyurethanes ( 15a–d ) and a poly(urea-urethane) 17 ), were synthesized from monomer 5 and their thermal properties and solubilities were determined. It was found that all investigated polymers decompose readily between 200°C and 250°C.     

Polymerization of anhydro sugar derivatives. Cationic polymerization of 5,6-anhydro-1,2-O-isopropylidene-α-D-glucofuranose and structure of the polymer

The cationic polymerization of 5,6-anhydro-1,2-O-isopropylidene-α-D -glucofuranose ( 1 ), containing an oxirane ring, gave a polymer whose structure was found to be poly(5,6-anhydro-1,2-O-isopropylidene-α-D -glucofuranose) ( 2 ). Polymerizations with phosphorus pentafluoride, boron trifluoride etherate, stannic chloride, or antimony pentachloride below 10°C for 0,04 to 240h gave yields of 51,7 to 97,5% of polymers with M?_n in the range of 1290 to 9500. Polymerization above 20°C produced insoluble gels. The specific rotations of the polymers changed with the polymerization conditions, being in the range of ?31,6° to ?15,0°. The mechanism of the epoxide polymerization of the 5,6-anhydro sugar derivatives is discussed.     

Block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate)

A series of block poly(ester-urethane) poly(3/4HB-HHxHO) urethanes (abbreviated as PUHO) based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB-diol) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate) (PHHxHO-diol) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent, with different 3HB, 4HB, HHxHO compositions and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by ¹H, ¹³C nuclear magnetic resonance spectrum (NMR), two-dimensional correlation spectroscopy (COSY (¹H, ¹³C) NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of water and CH₂I₂. DSC revealed that the poly(3/4HB-HHxHO) urethanes are almost amorphous with a little crystallinity (less than 6%) and T_g from ?23 °C to ?3 °C. The polyurethanes are more hydrophobic (water contact angle 88°–117°) than the P3/4HB and PHHxHO raw materials. The lactate dehydrogenase (LDH) assay and platelet adhesion determination showed that the obtained polyurethanes have much higher platelet adhesion property than raw materials and common biodegradable polymers polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB). Hydrophobicity and crystallinity degree are important factors to affect the platelet adhesion. All the properties can be tailored by changing the composition and segment length of prepolymers P3/4HB-diol and PHHxHO-diol.     

Facile Synthesis of Novel Thermo‐Responsive Polyvalerolactones with Tunable LCSTs

Thermoresponsive polymers have emerged as promising candidates for biomedical applications. Seven novel oligoethylene glycol (OEG) functionalized polyvalerolactones P1–P7 are synthesized from poly(α‐allyl‐δ‐valerolactone) via thiol‐ene addition post‐polymerization modification. All seven polymers exhibit thermoresponsive behavior with lower critical solution temperatures (LCSTs) ranging from 13.8 to 92.2 °C. Polymers P5–P7 are synthesized via thiol‐ene addition reaction using two thiol mixtures at three different ratios. LCSTs of P5–P7 fall in between those of P1 and P2 , and exhibit a linear relationship, indicating a tunable thermoresponsive system. This newly developed system offers great control for a desired thermoresponsive biocompatible, biodegradable polymeric system with desired LCSTs.     

Synthesis and characterization of poly(amide-imide)s containing 1,6-diamantane moieties in the main chain

A series of new poly(amide-imide)s were synthesized by direct polycondensation of the 1,6-bis(trimellitimido)diamantane ( 1 ) with various aromatic diamines in N-methyl-2-pyrrolidone (NMP) containing lithium chloride. The poly(amide-imide)s had inherent viscosities of 0.33–1.55 dL/g. The new polycyclic monomer 1 was synthesized from 1,6-diaminodiamantane with trimellitic anhydride. Dynamic mechanical analysis revealed polymers 3a – c to have main transitions at 385°C, 385°C, and 330°C, respectively. Moreover, these polymers were stable at high temperatures and maintained good mechanical properties (G′ ≈ 10⁸ Pa) up to temperatures close to the main transition well above 350°C. Their 5% weight loss temperatures ranged from 421 to 448°C in nitrogen, and from 417 to 426°C in air. A glass transition of poly(amide-imide)s 3 was not observed. Poly(amide-imide)s 3 (except 3e ) were soluble in NMP, pyridine, and o-chlorophenol. Some of the polymers ( 3a – c ) could be cast into flexible films. Their cast films had tensile strengths ranging from 35.5 to 46.9 MPa, elongations at break from 5.8 to 7.5%, and initial moduli from 1.8 to 2.1 GPa.     

Cationic polymerization of p-fluoro-α-methylstyrene

Boron trifluoride diethyl etherate-initiated polymerization of p-fluoro-α-methylstyrene at ?78°C in toluene, toluene/mixture of hexane isomers and toluene/hexane was carried out. Determination of the limiting viscosity numbers and molecular weights of some of the polymeric samples led to the evaluation of the Mark-Houwink constants for poly[1-(4-fluorophenyl)-1-methylethylene] at 25°C in benzene. Polymerization in 1,2-dichloroethane at ?15°C showed varying rates in the absence of added water. When the molar ratio of added water to the catalyst was 2,5 reproducible rates were observed. The IR spectrum of low-moleular weight polymers (obtained at ?15°C) contained bands corresponding to unsymmetrically disubstituted end-groups containing double bonds.     

Elastomers based on poly(hexafluoropropylene oxide) crosslinked via triazine groups

Poly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end-linking via triazine groups. The networks were characterised by NMR spectroscopy and by determination of the number of network chains from the shear modulus, and were shown to contain both triazine crosslinks and imidoylamidine links. The mechanical, thermal and chemical properties of the networks were investigated by a range of techniques. A network formed from fully difunctional poly(HFPO) had excellent elastomeric properties above ?15°C, and was thermally stable up to 270°C.     

Dynamic mechanical relaxations in poly(oxyoctamethylene)

Dynamic mechanical, calorimetric and X-ray diffraction measurements of poly(oxyoctamethylene) are carried out, in order to determine its viscoelastic relaxations and to elucidate the influence of the crystalline form of this polyether on its degree of crystallinity. The dynamic mechanical measurements were performed using a dynamic viscoelastometer at four frequencies ranging from 3,5 to 110 Hz, in the temperature range from ?150°C to 60°C. Two relaxations are observed. The one occurring at the lowest temperature (?139°C at 3,5 Hz) has an activation energy of 10 ± 1 kcal/mol (42 ± 4 kJ/mol) and is considered as the γ relaxation which takes place in all the polymers with three or more adjacent methylenic units. The other one appears at ?24°C and its activation energy is higher than 100 kcal/mol. The assignment of other of the two relaxations as glass transition of the polymer is discussed in context of the relaxation maxima of other members of the polyether series.     

Preparation and properties of poly(amide-imide)s derived from trimellitic anhydride, α-amino acids,and aromatic diamines

Four dicarboxylic acids containing one preformed imide ring were prepared by condensation of trimellitic anhydride with α-amino acids such as glycine, DL -alanine, DL -valine, and DL -lcucinc. These diacids were subsequently directly polycondensated with various aromatic diamines using triphenyl phosphite (TPP) and pyridine as condensing agents in N-methyl-2-pyrrolidone (NMP) containing calcium chloride, producing various aliphatic-aromatic poly(amide-imide)s with pendant alkyl groups. The resultant polymers have inherent viscosities in the range of 0,58–2,15 dL/g and were amorphous, as revealed by wide-angle X-ray diffractograms. All polymers were readily soluble in a variety of solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and NMP, and could be cast from their DMAc solutions into transparent, flexible, and tough films. All poly(amide-imide)s showed clear glass transition temperatures in the range of 181–313°C on the heating traces of differential scanning calorimetry (DSC). Almost all the poly(amide-imide)s exhibited no appreciable decomposition below 370°C, with 10% weight loss being recorded above 400°C in nitrogen and air. The polymers with larger side chain attached exhibited higher solubility, but lower glass transition temperature and initial decomposition temperature.     

Preparation and polymer-analogous reactions of a poly(vinyl sugar) with a C?C bond between sugar and polymer backbone

The synthesis of a new type of poly(vinyl sugar) is described whose polymer backbone is connected with the monosaccharide unit by a C—C bond. Such polymers can be obtained by radical initiation. They show good stability in polymer-analogous reactions in contrast to common poly(vinyl saccharides) whose sugar residues are bound to the polymeric chain by ester, ether, or glycoside bonds. Starting from 7,8-dideoxy-1,2;3,4-di-O-isopropylidene-α-D -galacto-oct-7-en-1,5-pyranos-6-ulose (1) polymers (P1) could be obtained by emulsion polymerization in high yields. Reduction of the keto group of P1 proceeded quantitatively and yielded poly(7,8-dideoxy-1,2;3,4-di-O-isopropylidene-D ,L -glycero-α-D -galacto-oct-7-en-1,5-pyranose) (P3) . In contrast to the following polymers without protecting groups these poly(vinyl ketones), which were soluble in tetrahydro-furan and toluene, did not follow a pure GPC-separation mechanism. The protecting groups of the poly(vinyl saccharides), either with or without keto groups, could be removed completely to give P2 and P4 . The solubility of the polymers P2 with galactose-functionalized side chains in water was limited to a weight-average molecular weight M?_w of 1 500 000 due to association phenomena of the monosaccharide units. Reduction of the hemiacetal group and of the keto group of P2 yielded poly(1,2-dideoxy-D ,L -glycero-D -galacto-oct-1-enitol) ( P5 ) with sugar alcohol side chains instead of a cyclic monosaccharide unit. Oxidation of the hemiacetal group of P2 and P4 furnished poly(7,8-dideoxy-D -galacto-oct-7-en-6-ulosonic acid sodium salt) ( P6 ) and poly(7,8-dideoxy-D ,L -glycero-D -galacto-oct-7-enonic acid sodium salt) ( P7 ), respectively. These polymers showed very high viscosities because of their polyelectrolyte character.     

Stereoregularity of polystyrene derivatives, 2. Poly(methoxystyrene)s Obtained by Anionic Catalysts.

The stereoregularity of poly(methoxystyrene)s was determined from the absorption of the aromatic C¹ carbon assuming a first-order Markov statistics holds for the polymerization as well as polystyrenes. The stereoregularity of poly(p-methoxystyrene)s prepared by sodium, potassium, or rubidium cations as catalysts in THF hardly varied and syndiotactic-rich polymers were obtained, whereas a random polymer was formed with cesium-naphthalene. In the polymerization of p-methoxystyrene in toluene, syndiotactic-rich polymers were obtained with butyllithium and random polymers were prepared by sodium or potassium cations as catalysts. The stereoregularity of poly(o-methoxystyrene)s prepared by sodium or potassium cations in tetrahydrofuran changed with the polymerization temperatures, and highly syndiotactic polymers were formed at?78°C. The structure of poly(o-methoxystyrene)s obtained in toluene, markedly depended on the initiators; that is, with increasing the size of the ionic radius of the counterions, the isotacticity of the polymers decreased. The mechanism of the polymerization and the substituent effect of the stereoregularity are discussed.     

Thermally Cross‐Linkable Poly(p‐xylylene)s for Advanced Low‐Dielectric Applications

A novel series of poly(p‐xylylene) homopolymer and copolymers containing thermally cross‐linkable cyclohexenyl moiety are prepared via base‐catalyzed Gilch route to yield high‐molecular‐weight polymers. The resulting polymers are highly soluble in a wide range of organic solvents and could be solution cast into flexible and transparent films. The polymers are thermally stable up to 350 °C and the glass transition temperature (T_g) is in the range of 136 ? 250 °C. They undergo thermal cross‐linking via the cyclohexenyl moiety. The cross‐linked polymer exhibits a high T_g of 294 °C, a low coefficient of thermal expansion (CTE) of 45 ppm K^?1. A low dielectric constant of 2.5 and a very low dielectric loss tan δ of 0.0004 at 1 GHz are obtained, which are superior to conventional interconnect polymers.     

Poly(ether-sulfone)s with indan structure elements

Various poly(ether-sulfone)s with 1,1,3-trimethylindan units along the main chain were synthesized from different diphenols and activated dihalogen monomers containing the 1,1,3-trimethylindan moiety. The indan-containing monomers were derived from 1,1,3-trimethyl-3-phenylindan by sulfonylation with 4-halobenzenesulfonyl chloride in the presence of the Friedel-Crafts catalysts. The polymers are amorphous with glass transition temperatures between 206 and 247°C, and decomposition temperatures above 460°C in air. Due to their solubility in common organic solvents such as tetrahydrofuran and chloroform, the polymers could be fully characterized by gel-permeation chromatography as well as ¹H- and ¹³C NMR spectroscopy.     

Hydrodynamic crossover in two-polymer mixtures from viscosity measurements

A very sharp crossover is observed in the variation of the reduced viscosity η_sp/c as a function of the concentration c for mixtures of 1:1 by weight mixtures of polystyrene and poly(methylmethacrylate) in benzene at 20°C and a 1:1 by weight mixture of poly(ethylene glycol) and polystyrene in benzene at 20°C. The crossover is attributed to the critical to the concentration of the two respective polymers in the solution and its sharpness is due to the incompatibility between the two different polymers.     

Synthesis and Properties of Novel Cardo Aromatic Poly(ether oxadiazole)s and Poly(ether‐amide oxadiazole)s

A series of polyhydrazides and poly(amide hydrazide)s bearing ether and cardo groups were prepared from three bis(ether carboxylic acid)s, 1,1‐bis[4‐(4‐carboxyphenoxy)phenyl]cyclohexane, 5,5‐bis[4‐(4‐carboxyphenoxy)phenyl]‐4,7‐methanohexahydroindan and 9,9‐bis[4‐(4‐carboxyphenoxy)phenyl]fluorene, or their diacyl chlorides with terephthalic dihydrazide, isophthalic dihydrazide and p‐aminobenzoyl hydrazide via the phosphorylation reaction or the low‐temperature solution polycondensation. The resulting hydrazide‐containing polymers exhibited inherent viscosities in the range of 0.35–0.71 dL·g^–1. All the hydrazide polymers were found to be amorphous as determined by X‐ray diffraction analysis and soluble in many organic polar solvents, and most of them afforded flexible and tough films by solvent casting. The hydrazide polymers had glass transition temperatures (T_g) between 157 and 197°C. All hydrazide polymers could be thermally converted into the corresponding oxadiazole polymers approximately in the region of 270–370°C, as evidenced by the DSC thermograms. The oxadiazole polymers showed a slightly enhanced crystallinity and an increase of T_g and a dramatically decreased solubility compared to their hydrazide prepolymers. They exhibited T_g's of 218–259°C and showed insignificant weight loss up to 450°C.