Synthesis and characterization of new aromatic polyesters containing pendent naphthyl units

Two bisphenols, viz., 4,4′‐[1‐(2‐naphthalenyl)ethylidene]bisphenol and 4,4′‐[1‐(2‐naphthalenyl) ethylidene]bis‐3‐methylphenol were prepared by condensation of commercially available 2‐acetonaphthanone with phenol and o‐cresol, respectively. A series of new aromatic polyesters containing pendent naphthyl units was synthesized by phase‐transfer‐catalyzed interfacial polycondensation of these bisphenols with isophthaloyl chloride, terephthaloyl chloride, and a mixture of isophthaloyl chloride/terephthaloyl chloride (50 : 50 mol %). Inherent viscosities of polyesters were in the range 0.83–1.76 dL g⁻¹, while number average molecular weights (M_n) were in the range 61,000–235,000 g mol⁻¹. Polyesters were readily soluble in organic solvents such as dichloromethane, chloroform, tetrahydrofuran, m‐cresol, pyridine, N,N‐dimethylformamide, N,N‐dimethylacetamide, and 1‐methyl‐2‐pyrrolidinone at room temperature. Tough, transparent, and flexible films were cast from a solution of polyesters in chloroform. X‐Ray diffraction measurements displayed a broad halo at 2θ ≅ 19° indicating the amorphous nature of polyesters. Glass transition temperatures of polyesters were in the range 209–259°C. The temperature at 10% weight loss (T₁₀), determined by TGA in nitrogen atmosphere, of polyesters was in the range 435–500°C indicating their good thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ionic polymers with tunable liquid‐crystalline properties

Side‐chain polyesters were synthesized from N‐octyl‐, N‐dodecyl‐ or N‐hexadecyl‐diethanolamine and succinic acid anhydride. These polyesters were then transformed into polyester hydrochlorides by protonation of the amino groups using different amounts of HCl (20–100 mol%). Above 60 mol% the reaction is not quantitative and a degree of protonation of up to 88% is obtained. The structures of the synthesized polyesters and their hydrochlorides were determined by ¹H nuclear magnetic resonance spectroscopy. The thermal properties of the synthesized polyesters and their hydrochlorides were also studied using differential scanning calorimetry in relation to the side‐chain length and the degree of polyester protonation. The polyester with octyl side chains and its hydrochlorides were amorphous liquids at room temperature, while the polyester and polyester hydrochlorides with hexadecyl side chains formed a smectic crystalline phase, S_mB, or its tilted analogues. The polyester with a dodecyl side chain was also an amorphous liquid at room temperature, while its hydrochlorides with various degrees of protonation were smectic liquid crystals, as determined by X‐ray diffraction. By simply varying the degree of protonation the liquid crystal isotropization temperature was increased from 32 °C to 82 °C. Copyright © 2011 Society of Chemical Industry     

Synthesis,characterization and biodegradation studies of chain‐coupled polyesters based on tartaric acid

A series of chain‐coupled polyesters based on tartaric acid was synthesized and characterized following a two‐step procedure. In the first step, tartaric acid based hydroxyl terminated polyesters with various alkane diols were prepared and then, in a second step, a chain‐coupling approach using hexamethylene diisocyanate was employed on the synthesized polyesters to prepare a series of chain‐coupled polyesters. The number‐average molecular weights (M_n) of the polyesters were found to vary in the range (4.8 ? 28.1) × 10³ g mol^?1. Thermomechanical studies demonstrate that the storage modulus of the chain‐coupled polyesters decreases with increasing polymethylene chain length which is attributable to enhanced flexibility. The isolation of bacteria on medium containing polymer as the sole source of carbon indicates the ability of the synthesized polyesters to be taken up by microorganisms for growth. © 2013 Society of Chemical Industry     

Aromatic polyesters containing pendent 4-(phenylsulfonyl)phenyl groups: synthesis and characterization

A new bisphenol, 1,1-bis-[(4-hydroxyphenyl)-1-(4-phenylsulfonyl)phenyl)]ethane (DPSBP) was synthesized starting from diphenylsulfide and was characterized by spectroscopic methods. DPSBP was polycondensed with isophthalic acid chloride (IPC), terephthalic acid chloride (TPC) and a mixture of IPC and TPC (50:50 mol%) by phase-transfer catalysed interfacial polymerization method to obtain aromatic polyesters containing pendent 4-(phenylsulfonyl)phenyl groups. A series of copolyesters was also obtained by polycondensation of varying molar proportions of DPSBP and bisphenol-A (BPA) with TPC. (Co)polyesters exhibited inherent viscosities in the range 0.56–1.57 dLg^?1 and number average molecular weights (Mn) were in the range 28,650–80,230 g/mol. Polyesters dissolved readily in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran and aprotic polar solvents such as N-methylpyrrolidone, and N,N-dimethylacetamide. Tough, transparent and flexible films of polyesters could be cast from their chloroform solutions. X-Ray diffraction studies indicated amorphous nature of aromatic polyesters. Polyesters showed T_g values in the range 223–257 °C while T₁₀ values were in the range of 469–484 °C indicating their excellent thermal stability.     

Chain extension of polybutylene adipate and polybutylene succinate with adipoyl‐ and terephthaloyl‐biscaprolactamate

HO‐terminated polybutylene adipate (HO‐PBA‐OH) with molecular weight from 1040 to 3540 and HO‐terminated polybutylene succinate (HO‐PBS‐OH) with intrinsic viscosity of 0.37 dL/g were synthesized through melt condensation polymerization from adipic acid or succinic acid with excess of butanediol. Chain extension of HO‐PBA‐OH or HO‐PBS‐OH with adipoyl biscaprolactamate and terephthaloyl biscaprolactamate was carried out at 200–240°C under reduced pressure. At the optimal conditions, chain‐extended PBA with M_n up to 50,700, and M_w up to 125,700 was synthesized, and the chain‐extended PBS with intrinsic viscosity of 1.25 dL/g was obtained. Meanwhile, p‐toluenesulfonic acid, SnCl₄ and zinc acetylacetonate catalyzed chain‐extending reaction of HO‐PBA‐OH and HO‐PBS‐OH was also studied. The chain‐extended polyesters were characterized by IR spectra, ¹H‐NMR spectra, and differential scanning calorimetry (DSC). The chain extension proceeds through the elimination of caprolactam rings in the chain‐extenders, the adipoyl groups or the terephthaloyl groups couple the hydroxyl‐terminated polyesters together and make the molecular weight of PBA or PBS increased, whether the acid catalyst such as p‐toluenesulfonic acid was present or not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis and characterization of new unsaturated polyesters containing cyclopentapyrazoline moiety in the main chain

3‐p‐Hydroxyphenyl‐6‐p‐hydroxybenzylidene cyclopentapyrazoline (III) and 3‐vanillyl‐7‐vanillylidene cyclopentapyrazoline (IV) were used as new starting materials for preparing new unsaturated polyesters. The polyesters were prepared by reacting (III) or (IV) with adipoyl, sebacoyl, isophthaloyl, and terephthaloyl dichlorides utilizing the interfacial polycondensation technique. The polyester samples have been characterized by elemental and spectral analyses. The polyesters have inherent viscosities of 0.55–0.97 dL/g. All the polyesters are semicrystalline and most of them are partially soluble in most common organic solvents but freely soluble in concentrated sulfuric acid. Their glass transition temperatures (T_g) range from 103.34 to 208.81°C, and the temperatures of 10% weight loss as high as 190 to 260°C in air, indicating that these aromatic polyesters have high T_g and excellent thermal stability. Doping with iodine dramatically raised the conductivity and produced dark brown colored semiconductive polymers with a maximum conductivity in the order of 3.1 × 10^?7 Ω^?1 cm^?1. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Organic acids catalyzed polymerization of ε‐caprolactone: Synthesis and characterization

Environmentally friendly organocatalytic synthesis of aliphatic polyesters was studied. The catalysis investigated is novel, and lends itself well to the potential production of valuable biodegradable products. The reactions were based on an organic acids‐catalyzed ring‐opening polymerization of ε‐caprolactone with fatty acid derivatives as the initiator and were performed in the absence of solvents. The chemical structures of the functionalized polymers were confirmed by ¹H and ¹³C‐NMR spectra. Polymers with different molecular weights, in the range 10,900–15,200 were obtained in the presence of fumaric acid as catalyst. The thermal properties of the functionalized PCLs were determined by modulated differential scanning calorimetry and thermogravimetric analysis. The MDSC results verified that the crystallinity and the melting point of the lipid‐functionalized polymers were lower than that of the unfunctionalized poly(ε‐caprolactone). The hydrolytic degradation of the functionalized polymer was also investigated. The result shows the degradation rate was affected by the presence of oleic acid derivatives in the polymer molecule. The lipid‐functionalized polymers synthesized by the metal‐free polymerization systems seem to be suitable biodegradable polyesters for use in biomedical and pharmacological applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrolysis‐improved thermosensitive polyorganophosphazenes with α‐amino‐ω‐methoxy‐poly(ethylene glycol) and amino acid esters as side groups

A series of hydrolysis‐improved thermosensitive polyorganophosphazenes with α‐amino‐ω‐methoxy‐poly(ethylene glycol) (AMPEG) and amino acid esters (AAEs) of ‘N,N‐systems’ was synthesized, and their properties were evaluated in comparison with the thermosensitive polyorganophosphazenes with methoxy‐poly(ethylene glycol) (MPEG) and AAEs of ‘O,N‐systems’, by means of ³¹P NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Most of the present polymers showed a lower critical solution temperature (LCST) in the range 32.0–79.0 °C, depending on the kinds of AAE, length of AMPEG and the mol ratio of the two substituents. These polymers exhibited higher LCSTs and faster degradation rates than the MPEG‐based polymers. The aqueous solution of poly(ethyl glycinate phosphazene)‐graft‐poly(ethylene glycol) [NP(GlyEt)_0.94(AMPEG350)_1.06]_n did not show an LCST, which is presumed to be due to its high hydrophilicity, in contrast to [NP(GlyEt)_1.01(MPEG350)_0.99]_n which showing an LCST at 77.5 °C. On the other hand, the polymers with a high content of AAE or with hydrophobic amino acids such as L ‐aspartic acid and L ‐glutamic acid, have shown a similar LCST to those of the MPEG‐based polymers. The half‐lives (t_1/2) for hydrolysis of [NP(AMPEG350)_1.06(GlyEt)_0.94]_n at pH 5, 7.4 and 10 were 9, 16, and 5 days, respectively, which are almost 2.5 to 4 times faster than that of the MPEG‐based polymers. The LCST of the present N,N‐polymers has been shown to be more influenced by salts such as NaCl (‘salting‐out’ effect) and tetrapropylammonium bromide (TPAB) (‘salting‐in’ effect) compared with the ‘O,N‐system’. Such differences of the ‘N,N‐systems’ from the ‘O,N‐systems’ in thermosensitivity, hydrolysis behavior and salt effect seem to be due to the higher hydrophilicity of the amino group in AMPEG. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of polyesters based on tartaric acid derivatives

A series of aliphatic polyesters based on tartaric acid and its derivatives were synthesized starting from naturally occurring L-tartaric acid. The hydroxyl groups of the tartaric acid derivatives were first protected and the polyesters were synthesized by bulk and solution polycondensation methods. Two classes of polyesters were synthesized and characterized, the first by polycondensation of dimethyl 2,3-O-isopropylidene-l-tartrate with various alkanediols, and the second by reaction of 2,3-O-isopropylidene-l-threitol with various diacid chlorides. Acid catalyzed deprotection of isopropylidene groups gave well-defined polyesters having pendant hydroxyl functional groups regularly distributed along the polymer chain. The number average molecular weights (M_n) of the polymers were found to vary in the range of 2.3-15.7 × 10³ g mol⁻¹. Differential scanning calorimetry (DSC) analysis showed the glass transition temperatures (T_g) of the polyesters varied from −36.1 °C to 17.9 °C on varying the chain length.     

Synthesis and characterization of polyesters based on 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane

Aromatic polyesters are of considerable interest because of their excellent mechanical properties, chemical resistance and thermal stability. However, most aromatic polyesters are difficult to process due to their high glass transition temperatures coupled with their insolubility in common organic solvents. The present article describes a series of organosoluble polyesters and copolyesters based on 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane. A series of new aromatic polyesters containing pendant pentadecyl chains was synthesized by interfacial polycondensation of 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane with terephthalic acid chloride (TPC), isophthalic acid chloride (IPC) and a mixture of TPC and IPC. A series of copolyesters was synthesized from 4,4′‐isopropylidenediphenol with TPC by incorporating 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane as a comonomer. Inherent viscosities of the polyesters and copolyesters were in the range 0.72–1.65 dL g^?1 and number‐average molecular weights were in the range 18 170–87 220. The polyesters and copolyesters containing pendant pentadecyl chains dissolved readily in organic solvents such as chloroform, dichloromethane, pyridine and m‐cresol and could be cast into transparent, flexible and apparently tough films. Wide‐angle X‐ray diffraction data revealed the amorphous nature of the polyesters and copolyesters. The formation of loosely developed layered structure was observed due to the packing of pendant pentadecyl chains. The temperature at 10% weight loss, determined using thermogravimetric analysis in nitrogen atmosphere, of the polyesters and copolyesters containing pendant pentadecyl chains was in the range 400–460 °C. The polyesters and copolyesters exhibited glass transition temperatures in the range 63–82 °C and 177–183 °C, respectively. Copyright © 2010 Society of Chemical Industry     

Flame retardant finishing of cotton fleece fabric: Part V. Phosphorus‐containing maleic acid oligomers

The high flammability of cotton fleece makes it necessary to apply a flame retardant system on cotton fleece so that it can meet the federal regulation ‘Standard for the Flammability of Clothing Textiles’ (16 CFR 1610). The objective of this research was to reduce the flammability of cotton fleece using the phosphorus‐containing maleic acid oligomers (PMAO) synthesized by aqueous free radical polymerization of maleic acid. We found that PMAO can be bound to cotton fleece by esterifying with cotton cellulose with sodium hypophosphite as the catalyst. Both the 45^° flammability and limiting oxygen index data indicated that the treatment of cotton using PMAO reduced the flammability of cotton fleece. The micro‐scale combustion calorimetric data revealed that PMAO reduced the peak heat release rate and heat release capacity of the treated cotton woven fabric. The cotton fleece treated with PMAO/NaH₂PO₂ passed the federal flammability test (16 CFR Part 1610) and achieved ‘Class 1’ flammability. The PMAO bound to cotton was durable to multiple home laundering cycles. The treated fleece also showed high strength retention with little change in fabric whiteness. The use of triethanolamine as an additive modestly enhanced the performance of PMAO with no significant changes in fabric physical properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of α‐amino acid‐containing polyester: poly[(ε‐caprolactone)‐co‐(serine lactone)]

Novel polyesters, poly[(ε‐caprolactone)‐co‐(N‐trityl‐L ‐serine‐β‐lactone)]s, were prepared by copolymerizing ε‐caprolactone (CL) with N‐trityl‐L ‐serine‐β‐lactone (TSL) using ZnEt₂ as the catalyst. The number‐average molecular weights were determined which ranged from 2.7 × 10⁴ to 4.9 × 10⁴ Da with dispersity values ranging from 1.6 to 1.8. The structures of the copolymers were investigated by means of ¹H NMR, ¹³C NMR and infrared spectroscopies, thermogravimetric analysis and differential scanning calorimetry. The results indicated that CL and TSL monomer units were randomly distributed within the copolymer backbone structures and the ratios of TSL to CL in the copolymers were close to those in the feeds. After removal of the trityl group under mild condition, a new polyester with side amino groups provided by serine units was obtained. L929 cell culturing test indicated good biocompatibility of the polyester with or without protective groups. © 2012 Society of Chemical Industry     

Rheological properties of hydroxyl‐terminated and end‐capped aliphatic hyperbranched polyesters

The rheological behavior of two series of aliphatic hyperbranched (HB) polyesters, based on 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) and di‐trimethylol propane (Di‐TMP) as a tetrafunctional core, was studied. The effect of the size (pseudo‐generation number, from second to eight) and structure on the melt rheological properties was investigated for a series of hydroxyl‐terminated HB polyesters. In addition, the influence of the nature and degree of modification of the terminal OH groups in a series of fourth‐generation polyesters end‐capped with short and long alkyl chains and some aryl groups on the rheological properties was analyzed. The time–temperature superposition procedure was applied for the construction of master curves and for the analysis of the rheological properties of HB polyesters. The data obtained from WLF analysis of the HB polyesters showed that the values of the thermal coefficient of expansion of free volume α_f and the fractional free volume at the glass transition temperature, f_g, increase with increasing size of the HB polyesters. It was shown that the modified HB polyesters exhibited lower T_g and T_G′=G″ temperatures, above which viscous became dominant over elastic behavior. From an analysis of the master curves of the modified HB polyesters, it was observed that with increasing degree of modification, both storage and loss modules and complex dynamic viscosity and apparent energy for viscoelastic relaxation decrease, because of reduced intermolecular hydrogen interactions. They do not exhibit a plateau of rubbery behavior, which confirms that no entanglements are present and that the molar masses are below the critical molar mass. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41479.     

Investigation into the solution properties of hyperbranched polymer

The solution properties of hydroxyl terminated hyperbranched aliphatic polyesters and their acetyl derivatives have been studied by measuring viscosity parameters. The polarity of terminated groups of molecules is the most important factor affecting their properties. The intrinsic viscosity [η] cannot reflect the real monomolecular hydrodynamic volume of hydroxyl group-terminated hyperbranched polymer due to the strong intermolecular forces which lead to the formation of stable clusters. The intermolecular association constant K_M depends not only on molecular weight, but also on the polarity of end-groups. However, the dynamic contact concentration C_S can be determined accurately from reduced viscosity versus concentration plots. The reason why the intrinsic viscosity does not change linearly with the generation of the hyperbranched aliphatic polyesters is explained using ‘free-draining’ and ‘non-draining’ models. © 2001 Society of Chemical Industry     

Characterization of hyperbranched polyol polyesters based on 2,2‐bis (methylol propionic acid) and pentaerythritol

Hyperbranched polyesters (HBPs) of fourth and fifth generation were synthesized by procedures involving one step (HBP4, HBP5), step by step (HBP4P, HBP5P), and combination of both of them (HBP1‐4, HBP1‐5) using 2,2‐bis(methylol)propionic acid (DMPA), pentaerythritol (PE), and acid catalysis. The characterization of the polyesters was done by nuclear magnetic resonance (NMR), rheology on solution, Fourier transform infrared spectroscopy (FTIR), and acid and hydroxyl values. The degree of branching of polyesters (DB) and the average molecular mass and polymerization degree _NMR were calculated by Frey and Fréchet methods and (DP)_NMR, respectively, being higher for HBP4P sample. The molecular structure of polyesters depends mainly on of the synthesis method. The hydroxyl values were larger than 430 mg/g KOH for all HBPs, and the conversion was controlled between 90 and 93% to avoid excessive cyclization reactions. The steady shear viscosities at different temperatures and at 41.77 s^?1 shear rate were measured for all HBPs solutions in dimethyl formamide (DMF) showing a shear thickening behavior. The flow activation energies (E_a) were calculated by Arrhenius equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hyperbranched polyesters based on hydroxyalkyl‐lactones via thiol‐ene click reaction

The preparation of AB₂ monomers via thiol‐ene click reaction from six‐ and seven‐membered unsaturated lactones is described. The hydroxyl‐functionalized valerolactone was prepared by use of Michael thiol‐ene‐addition reaction starting from 2‐mercaptoethanol and 3‐methylenetetrahydro‐2H‐pyran‐2‐on. The hydroxyl‐functionalized caprolactone was prepared radically from 2‐mercaptoethanol and 7‐allyloxepan‐2‐one. Both AB₂ monomers were polymerized via ring opening in the presence of tin(II)‐2‐ethylhexanoate (Sn(Oct)₂) as a catalyst yielding the hyperbranched polyesters. The new hyperbranched polyesters were analyzed by ¹³C NMR spectra to determine the degree of branching. © 2014 Society of Chemical Industry     

New polymer syntheses: 10. Syntheses of high molecular weight poly(4-hydroxybenzoate)s by bulk condensations of 4-hydroxybenzoic acids

The condensation of 4-hydroxybenzoic acid by means of various carboxylic acid anhydrides, acid chlorides and diphenylcarbonate has been investigated. All condensations were conducted in ‘one-pot procedures’. The average degrees of polymerization ($\text{DP}$) were determined by means of ¹H nuclear magnetic resonance (n.m.r.) spectroscopic end-group analyses. The bulk condensation of 4-hydroxybenzoic acid by means of acetic anhydride at temperatures between 320° and 350°C was found to be the simplest and least expensive procedure. Yields between 97 and 99% and $\text{DP}$ up to 300 were obtained in this way. Bulk condensations of purified acetoxybenzoic acid or condensations of 4-hydroxybenzoic acid with acetic anhydride in an inert solvent gave similar yields and $\text{DP}$. Also, the bulk condensations of 3,5-dimethyl-4-hydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 3,5-dichloro-4-hydroxybenzoic acid and 3,5-dibromo-4-hydroxybenzoic acid by means of acetic anhydride gave yields above 90%. However, the $\text{DP}$'s varied greatly with the nature of the substituents. ‘One-pot procedures’ using a variety of phosphorus derivatives as condensing reagents did not yield pure polyesters. The differential scanning calorimetry (d.s.c.) curves of the substituted poly(4-hydroxybenzoate)s do not show any endotherm, although X-ray diffraction measurements indicate a high degree of crystallinity. The thermogravimetric analyses demonstrate that the thermal stability depends largely on the synthetic procedure.     

Synthesis and properties of thio‐containing poly(ether ether ketone)s

A series of thio‐containing poly(ether ether ketone) (PEESK) polymers was synthesized by the introduction of thio groups from 4,4′ thiodiphenol (TDP) into the poly(ether ether ketone) (PEEK) structure via reaction between the phenol and aromatic fluoride groups. The effect of the thio groups on the properties of the PEESK materials was investigated. Differential scanning calorimetry (DSC) analysis and X‐ray diffraction (XRD) patterns show a depression in the crystallinity of the PEESKs with incorporation of the content of thio groups in the backbones. The crystalline structure was identified as an orthorhombic structure with lattice constants of a = 7.52 Å, b = 5.86 Å and c = 10.24 Å for all crystallizable PEESKs. The crystalline structures of the thio‐containing PEEK polymers were the same as that of the neat PEEK, which means the thio‐containing block in the whole thio‐containing PEEK molecule is almost excluded from the crystalline structure and the crystals are completely formed by ‘non‐thio’ blocks only. Due to the glass transition temperature (T_g) and melting temperature (T_m) depression with increase in the TDP content in the reaction system, the processability of the resultant thio‐containing PEEKs could be effectively improved. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of a thermotropic liquid crystalline hyperbranched polyester

BACKGROUND: Hyperbranched polymers have received increasing attention in the fields of medicine, homogeneous catalysis and materials science. Hydroxyl‐functional aliphatic polyesters are one of the most widely investigated families of hyperbranched polymers. The research reported here is based on the preparation of a novel hyperbranched polyester and the modification of its terminal hydroxyl groups by biphenyl mesogenic units. RESULTS: 2,2,6,6‐Tetramethylolcyclohexanol as a core and 8‐[4′‐propoxy(1,1‐biphenyl)yloxy]octanoic acid as a mesogenic unit were synthesized. A hyperbranched polyester (HPE) was synthesized in one step and subsequently substituted by reaction of its terminal hydroxyl groups with the biphenyl mesogenic units to yield a novel liquid crystalline hyperbranched polyester (HPE‐LC). The chemical structures of all compounds were confirmed using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. The thermal behavior and the mesogenic properties of the biphenyl mesogenic unit and HPE‐LC were investigated using differential scanning calorimetry, polarized optical microscopy and wide‐angle X‐ray diffraction. The results demonstrated that the degree of branching of the HPE is ca 0.63. Both HPE‐LC and the biphenyl mesogenic unit exhibit mesomorphic properties, but HPE‐LC has a lower isotropic transition temperature and a wider transition temperature range than the biphenyl mesogenic unit. CONCLUSION: A novel liquid crystalline hyperbranched polyester was successfully synthesized, which exhibits mesomorphic properties. This polymer has good solubility in highly polar solvents and good thermal stability. Copyright © 2009 Society of Chemical Industry     

Synthesis and enzymatic degradation of high molecular weight aliphatic polyesters

The aliphatic polyesters with high molecular weight have been prepared according to two methods. First is the synthesis of the polyesters by polycondensation of dimethyl succinate (DMS) with 1,4‐butanediol (BD) using various metal alkoxides as a catalyst. Among the metal alkoxides used, titanium tetraisopropoxide [Ti(OiPr)₄] gave the best results (highest molecular weight and yield). Thus, we have prepared aliphatic polyesters using a variety combinations of diesters [MeOOC—(CH₂)_x—COOMe, x = 2–8] with BD by the catalysis of Ti(OiPr)₄. The polyesters with high number‐average molecular weight (M_n > 35,000), except dimethyl adipate (DMA, x = 4)/BD polyester (M_n = 26,900), were obtained in high yield. The melting temperatures (T_m) of polyesters were relatively low (43.4–66.8°C) except that (115.6°C) of the DMS/BD polyester. Second is the synthesis of high molecular weight polyesters by chain extension reaction of lower molecular weight (M_n = 15,900–26,000) polyesters using hexamethylene diisocyanate (HDI) as a chain extender. The M_n values of chain‐extended polyesters consequently increased more than two times (M_n = 34,700–56,000). The thermal properties of polyesters hardly changed before and after chain extension. Enzymatic degradations of the polyesters were performed using three different enzymes (cholesterol esterase, lipase B, and Rhizopus delemar lipase) before chain extension. The enzymatic degradability varied depending on both thermal properties of polyesters [melting temperature and heat of fusion (crystallinity)] and the substrate specificity of enzymes, but it was the following order: cholesterol esterase > lipase B > R. delemar lipase. The ¹H‐NMR spectrum of water‐soluble degraded products of the polyester indicated that the polyester was degraded into a condensation product of diol with diester in a monomer form. The enzymatic degradation of chain extended polyesters was slightly smaller than that before chain extension, but proceeded steadily. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 340–347, 2001