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Abstract: Nanocomposites of poly(hexamethylene terephthalate) (PHT) and montmorillonite organo-modified with alkylammonium cations bearing two primary hydroxyl functions, i.e., Cloisite® 30B (CL30B) were synthesized. Organoclay incorporation was performed either by dispersion in the PHT matrix via melt blending or by in situ ring-opening polymerization of hexamethylene terephthalate cyclic oligomers c(HT). An additional procedure combining the two methods, preparation of a highly enriched inorganic “PHT–CL30B” nanohybrid masterbatch by in situ ring-opening polymerization and blending of the masterbatch with additional PHT was explored. The obtained nanocomposites contain 3% (w/w) of inorganics and displayed a mixture of intercalated morphology and exfoliated nanolayers as evidenced by X-ray diffraction and transmission electron microscopy. The nanocomposite obtained by the masterbatch technique exhibited a higher degree of exfoliation and displayed slightly higher glass transition temperatures, better mechanical properties and higher flame resistance. The improved results achieved with the “masterbatch route” are a consequence of the reactions occurring between the nanocomposite constituents allowing for the grafting of PHT chains onto the organoclay surface. [Copyright &y& Elsevier]

Abstract: The pair of stereoisomeric polyamides PA-6dAr and PA-6lAr, as well as the racemic stereocopolyamide PA-6dlAr was synthesized from hexamethylenediamine and 2,3,4-tri-O-methyl-arabinaric acid (d, l and their equimolar mixture, respectively). All these polyamides were aregic, thermally stable and display high crystallinity. The combined analysis by X-ray and electron diffraction revealed that the all three polyamides adopted the same crystal structure, which consists of a rhombic lattice with the chains in a highly contracted conformation capable of accommodating efficiently the sugar moiety in the space. The Avrami kinetic analysis revealed that copolyamide PA-6dlAr crystallized isothermally much slower than the optically homogeneous polyamides. A parallel study carried out on the racemic mixture of PA-6dAr and PA-6lAr evidenced that this mixture has a crystal structure and displays a thermal behavior similar to their separated components, and that its crystallization rate is intermediate between them and the racemic copolyamide PAdlAr. [Copyright &y& Elsevier]

• Polyester-polypeptide diblock copolymers are synthesized avoiding organo-metals. • Both copolymer molecular weight and composition are well-controlled in the synthesis. • In the solid state the copolymers have the two blocks separated and orderly arranged. • The copolymers become self-assembled in water as spheres of 200–400 nm diameter. • They are precursors for charged copolymers suited for stimuli-responsive biomaterials. Diblock copolymers (PPDLx- b -pPAAy) were prepared from ω-pentadecalactone and l -glutamic acid or l -lysine amino acids by ring opening polymerization initiated by amino groups. Telechelic amino-ended poly(ω-pentadecalactone) with a length of 15–20 repeating units was firstly synthesized by enzymatic polymerization by means of CALB and then used as macroinitiator for the polymerization of the N -carboxyanhydrides of the two α-amino acids conveniently protected as benzyl and ε N -carbobenzoxy derivatives, respectively. The molecular weight of the polypeptide block was accurately controlled by adjusting the amino acid/macroinitiator ratio used in the feed. Copolymers with M n ranging between ∼5000 and ∼40,000 g·mol−1 and varying ester/peptide ratio were obtained and characterized in detail by GPC and NMR spectroscopy. The thermal properties of these copolymers were evaluated by TGA and DSC, and their structure in the solid-state including their response to heating, were examined by FTIR and XRD at variable temperature. It was shown that the polypentadecalactone segment was crystallized for all compositions and that the polypeptide counterpart adopted a two-dimensional hexagonal packing of α-helices at temperatures above melting of the polyester block. SAXS revealed the presence of a biphasic nanostructure with a repeating distance of 27 nm for the case of glutamic-based copolymers. It was demonstrated that both glutamic and lysine-based PPDL x - b -pPAA y copolymers could self-assemble in well-shaped nanospheres with a diameter in the ∼200–400 nm range and a negative zeta-potential. [ABSTRACT FROM AUTHOR]

The preparation of cyclic ethylene and butylene 2,5-furandicarboxylate oligoesters and their conversion to furan-based polyesters poly(ethylene furanoate) (PEF) and poly(butylene furanoate) (PBF) by ring-opening polymerization (ROP) are described. The cyclic oligoesters were obtained in high yields by both high dilution condensation and thermal cyclodepolymerization methods, and they consisted of mixtures of small size species. Cyclic dimer, trimer and tetramer oligoesters were isolated by semipreparative chromatography and found to be crystalline compounds melting within the 140–200 °C range. ROP catalyzed by Sn(Oct) 2 of both mixtures and individual species afforded PEF and PBF with weight-average molecular weights between 50,000 and 60,000 g mol −1 . Polymerization rate was found to be higher for butylene than for ethylene cyclic oligofuranoates, and also to increase slightly as cycle size decreased. The thermal properties of PEF and PBF prepared by ROP were in full agreement with those reported for these polyesters obtained by melt polycondensation. [ABSTRACT FROM AUTHOR]

Abstract: Nanocomposites made from stoichiometric complexes of bacterial polyglutamic acid with alkyltrimethyl ammonium surfactants and Cloisite 30B were prepared for a wide range of compositions spanning from 3% to 90% of inorganic contents. The TGA analysis ascertained the compositions of the nanocomposites and revealed that their thermal decomposition proceeded through a mechanism similar to that of the complexes. Their structure and nanomorphology were examined by DSC, XRD and TEM which evidenced an exfoliated structure for low contents in Cloisite (less than 10%). Nanocomposites with high Cloisite compositions consisted of mixtures of isolated clay lamellae with stacks of intercalated polyacid-Cloisite layers heterogeneously dispersed in a disordered complex matrix. Both thermal and mechanical properties of the surfactant complexes changed steadily with the increasing amount of added nanoclay. An exceptional mechanical tensile behavior was however observed for the composite containing 3% of Cloisite, which was associated to the occurrence of a fully exfoliated structure. [Copyright &y& Elsevier]

Abstract: Poly(hexamethylene terephthalate) (PHT)/carbon nanotubes (CNT) nanocomposites containing 1% and 3% (w/w) of filler were prepared by two procedures: in situ ring-opening polymerization of hexamethylene terephthalate cyclic oligomers in the presence of CNT and melt blending of PHT/CNT mixtures. Arc discharge multiwalled carbon nanotubes, both pristine (MWCNT) and hydroxyl functionalized (MWCNT-OH), were used. The objective was to evaluate the effect of preparation procedure, nanotube side-wall functionalization and amount of nanotube loaded on properties of PHT. All nanocomposites showed an efficient distribution of the carbon nanotubes within the PHT matrix but interfacial adhesion and reinforcement effect was dependent on both functionalization and nanotubes loading. Significant differences in thermal stability and mechanical properties ascribable to functionalization and processing were observed among the prepared nanocomposites. All the prepared nanocomposites showed enhanced crystallizability due to CNT nucleating effects although changes in melting and glass transition temperatures were not significant. [Copyright &y& Elsevier]

Abstract: Poly(hexamethylene terephthalate) was cyclo-depolymerized in solution by heating to yield a fraction of cyclic oligomers of hexamethylene terephthalate (c(HT)2–5) with a content around to 95% in dimer to pentamer. Ring-opening polymerization in the melt of c(HT)2–5, either neat or in mixtures with ε-caprolactone (CL) covering a range of HT/CL ratios from 9/1 to 1/9 was carried out to produce polyesters with molecular weights above 30,000 in high yields. The copolyesters had a comonomer composition according to the feed and the microstructure evolved from random to blocky as the content in CL increases. The thermal and mechanical properties of the copolyesters were evaluated for a variety of compositions. Results obtained in this work were compared to those previously obtained by us in the ring-opening copolymerization of CL with a cyclic oligomeric fraction enriched in hexamer and heptamer (c(HT)6–7). Although the polyesters resulting from the use of these two fractions were similar, significant differences were found in polymerization rate evidencing a lower reactivity of c(HT) n with decreasing values of n. [Copyright &y& Elsevier]

Abstract: The hydrolytic degradation of a series of homo- and co-polyesters analogous to poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI), prepared from carbohydrate-based monomers, was studied. The degradation process was carried out at temperatures of approximately 10°C above the T g of the polymers. All the studied polyesters were found to degrade at significant rates, and degradability showed a clear dependence on the configuration of the sugar units present in the polymer chain. No weight loss was detected upon degradation, apparently due to the non-solubility of the degraded products in the aqueous incubation medium. Hydrolysis of co-polyesters took place preferentially by cleavage of the ester groups of the sugar units. [Copyright &y& Elsevier]

A biodegradability study of several aromatic building blocks used for the preparation of poly(ethylene terephthalate) copolymers of technical interest has been carried out. They include the dimethyl esters of terephthalic, 5-nitroisophthalic, and nitroterephthalic acid, as well as the 2-hydroxyethyl esters of the first two mentioned acids. Biodegradability was first evaluated on solid agar for a number of culture collection strains. Only 7 out of the 24 assayed strains showed degrading activity on some substrates. The degrading microorganisms were then isolated from environmental samples using an enrichment culture technique. Most of the environmental isolates showing degrading capability belonged to the genus Pseudomonas or Bacillus. Biodegradation with commercial lipases, esterases and proteases showed that most of the 16 tested enzymes degraded some of the substrates. [Copyright &y& Elsevier]

The hydrolytic degradation at 80 °C of a series of poly(ethylene terephthalate) (PET) copolymers containing 5-nitroisophthalic (PETNI) and nitroterephthalic (PETNT) units is described. The degradation process was followed by weighting, viscometry, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) spectroscopy. The nitrated copolyesters degraded faster than semicrystalline and amorphous PET, and the degradation rate increased with the content of nitrated units. DSC measurements showed that the melting temperature of the semicrystalline samples increased slightly upon hydrolytic degradation, whereas the degree of crystallinity remained essentially unchanged. NMR spectroscopy revealed that hydrolysis occurred preferentially by cleavage of the ester groups of the nitrated units, and that most of the degradation products remained in the degraded polymer samples. [Copyright &y& Elsevier]

• Ionic macrolactone-amino acid diblock copolymers were prepared from neutral precursors. • The two copolymer blocks were able to adopt ordered structures separately. • The copolymers became self-assembled in water in 100–200 nm diameter particles. • Glu-containing copolymers were efficient for loading and pH-mediated releasing of DOX. • Lys-containing copolymers entrapped and condensed DNA by forming ionic polyplexes. Two sets of ionically charged polypentadecalactone-polypeptide diblock copolymers (PPDL x - b -PAA y , with x = 15 or 20 and y ranging from 30 to 200), one containing α-L-glutamic acid (LGA) and the other containing α-L-lysine (LL), were obtained from their respective precursors with the side groups of LGA and LL protected as γ O -benzyl and ε N -carbobenzoxy, respectively. The copolymers were semicrystalline with the polyester block crystallized in the usual pseudo-rhombic lattice and the polypeptide in the α-helix or β-sheet conformation depending on the amino acid and the length of the block. Copolymers with PAA blocks with y ≥ 80 were water-soluble and they adopted the α-helix conformation in the aqueous medium when they are in the non-ionized state. Both LGA and LL containing copolymers self-assembled in nanoparticles with a size between 150 and 180 nm in diameter. PPDL- b -PLGA nanoparticles were able to load DOX with an efficiency of ~70% whereas PPDL- b -PLL displayed a noticeable capacity for condensing DNA. In both cases hosting was based on the ionic complexation taking place between the ionized copolymer and the guest compound. Accordingly DOX release rate was found to be noticeably depending on pH. [ABSTRACT FROM AUTHOR]

Ethyl α N -lauroyl l -arginate hydrochloride (LAE) was coupled with hyaluronic acid (HyA) to form ionic complexes with LAE to HyA ratios of 1:1 and 1:2. The complexes were extensively characterized by FTIR and NMR spectroscopies and their thermal properties evaluated by thermogravimetry and calorimetry. Thin films prepared from these complexes by casting displayed a smectic-like structure based on an ordered arrangement of LAE and HyA layers with a nanometric periodicity of 3.8–3.9 nm. Films immersed in water at pH 7.4 and 5.5 dissociated to deliver free LAE to the environment and reaching the equilibrium in few hours. The biocide activity of these films against both Gram-positive and Gram-negative bacteria was preliminary assessed by the liquid medium method, and shown to be notable in both cases. The antibacterial property of the complexes was found to increase with the content of LAE and to be particularly efficient against Gram-negative S. enterica bacteria. [ABSTRACT FROM AUTHOR]

In this paper, the preparation of PBS- ran -PCL copolyesters by enzymatic ring opening polymerization is presented for the first time. The copolyesters were produced in a wide composition range and free of metallic contaminants, so they may be regarded as potential biomaterials. The copolymers have been characterized by proton and carbon nuclear magnetic resonance ( 1 H and 13 C NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM) and wide angle X-ray scattering (WAXS). The PBS- ran -PCL copolyesters were able to crystallize in the entire composition range and displayed a pseudo-eutectic region. Most copolymers away from the pseudo-eutectic region exhibited a single crystalline phase (PBS-rich or PCL-rich crystalline phase), while within the pseudo-eutectic region the copolymers were double crystalline. Observations by PLOM, during isothermal crystallization showed that both nucleation density and spherulitic growth rate of the copolyesters are determined by the component that constitutes the majority phase. WAXS studies revealed that d spacings of selected crystallographic planes depend on composition. Therefore, both DSC and WAXS results suggest that the copolymers are probably isodimorphic, as the PBS-rich crystalline phase may contain small inclusions of PCL co -units, while the PCL-rich crystalline domains may also contain a minor quantity of PBS co -units inside. [ABSTRACT FROM AUTHOR]

ABA triblock copolyesters were synthesized by ring-opening polymerization (ROP) of l -lactide in solution initiated by a telechelic d -glucose-based polyester macroinitiator. The macroinitiator with a number-average molecular weight about 2500 g mol −1 was synthesized by non-stoichiometric polycondensation in the melt of 2,4:3,5-di- O -methylene- d -glucitol and dimethyl succinate. Two triblock copolyesters of M n ranging between ∼6000 and ∼9000 g mol −1 , and differing in the length of the polylactide blocks were prepared. These copolyesters started to decompose when heated at ∼220 °C and degraded slowly upon aqueous incubation under physiological conditions. They did not display any perceivable crystallinity and showed a single glass transition temperature ( T g ) around 60 °C with the higher value corresponding to the larger content in glucitol units. The copolyesters were able to form nanoparticles with average diameters of ∼100–130 nm and satisfactory dispersity. The effect of the block lengths on size, ζ -potential values and physical stability of the nanoparticles was evaluated. A molecular dynamics simulation study allowed modelling the two-phase structure of the nanoparticles and evidenced the preference of the glucose-based block to be peripherally located. [ABSTRACT FROM AUTHOR]

A series of ionic complexes with a comb-like architecture and a nearly stoichiometric composition were prepared from bacterial poly(γ, dl -glutamic acid) (PGGA) and alkyltrimethyl phosphonium bromides ( n ATMP·Br) bearing long linear alkyl chains with even numbers of carbon atoms ( n ) ranging from 12 to 22. The n ATMP·PGGA complexes were non-water soluble but readily soluble in organic solvents, and they displayed a high thermal stability. Combined DSC and XRD studies revealed that these complexes adopted an amphiphilic layered structure with the polypeptide chain and the alkyl chain separated in two differentiated phases with a nanoperiodicity that increased steadily with the length of the alkyl chain. The paraffinic phase was found to be partially crystallized in an extent that decreased with n , so that complexes with n = 12 and 14 did not show any sign of crystallinity whereas those with n from 16 to 22 showed crystalline melting in the ∼30–70 °C range. The structural transitions taking place by temperature effects were characterized by simultaneous SAXS/WAXS using synchrotron radiation at real time. In all cases, a shortening of the layer periodicity occurred upon heating with recovering of the initial structure after cooling. n ATMP·PGGA with n ≤ 16 showed strong antimicrobial activity against both E. coli and S. aureus, a property that could be related to the weak dissociation of the complexes happening upon incubation in water. The structure and properties of these complexes where comparatively discussed taking as reference their analog complexes made from PGGA and alkyltrimethylammonium bromides already studied by us. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and comparative evaluation of properties of two series of cationic PBS copolyesters bearing respectively ammonium and tributylphosphonium side groups, are reported. The copolyesters with contents in ionic units up to 50 mole-% as well as the fully ionic homopolyesters were prepared by polycondensation in the melt catalyzed by CALB or TBT. Their M n ranged between 20,000 and 5000 g mol −1 depending of composition and the type of ionic group that is involved. All the copolyesters were non-water soluble and showed good thermal stability. They were semicrystalline with melting temperatures and enthalpies decreasing with the ionic contents. The interactions interplayed by the ionic groups restricted largely the molecular mobility and caused a significant increase in the melt viscosity and glass transition temperature of PBS and a decrease in crystallization rate. Both ammonium and phosphonium containing PBS copolyesters were able to be coupled with sulfonated PBS to generate ionic polymer blends with modified crystallizability. The presence of both ammoniums and phosphoniums provided PBS with remarkable antimicrobial activity against gram-positive and gram-negative bacteria. [ABSTRACT FROM AUTHOR]

The two cyclic acetals, 2,3-di- O -methylene- l -threitol and dimethyl 2,3-di- O -methylene- l -threarate, were used for the synthesis of two series of PBS copolyesters differing in which unit, butylene or succinate, was replaced, in addition of the corresponding parent homopolyesters. Polycondensation reactions were carried out in the melt affording polymers with satisfactory molecular weights. Copolyesters were prepared with contents in tartaric acid-based units over the whole range of compositions and they all had a random chemical microstructure. The physical properties of the novel copolyesters varied widely depending not only on their composition but also on the type of unit that was replaced. They showed higher glass transition ( T g ), lower melting temperatures ( T m ), and lower crystallinity compared to the parent PBS homopolyester. Regarding mechanical properties, the presence of the stiff cyclic acetal units in the PBS chain caused an increase in the elongation at break and also a reduction in both elastic modulus and tensile strength of the polyester. Upon copolymerization the PBS notably increased its hydrolytic degradability and more slightly its susceptibility to be degraded by lipases. [ABSTRACT FROM AUTHOR]

Abstract: Two cyclic acetal compounds, 2,3-O-methylene L-threitol and dimethyl 2,3-O-methylene L-threarate, both coming from naturally-occurring tartaric acid, were used as comonomers to replace ethylene glycol and dimethyl terephthalate respectively, in the preparation of PET-based copolyesters by polycondensation in the melt. Synthesis results, structure and thermal properties of the two afforded copolyester series were evaluated and compared regarding composition and type of comonomer used in each case. All the copolyesters had a random microstructure and molecular weights in the 25,000–35,000 g·mol−1 range. Their thermal properties varied logically with composition along each series but they significantly changed according to which acetal comonomer was used. PET copolyesters made from acetalized L-threitol displayed thermal stability and T g comparable to PET, whereas these two properties were depressed in the copolyesters containing threarate units. Both types of copolyesters were able to crystallize for contents in tartaric acid derived units up to around 30% by adopting the crystal structure of PET. Crystallization rates and melting temperatures decreased with copolymerization in the two series but this effect was more noticeable in copolyesters made from threitol. [Copyright &y& Elsevier]

Abstract: Stoichiometric ionic complexes of bacterial poly(γ-glutamic acid) with the cationic N-octadecyl and N-docosyl-N,N,N-trimethylammonium surfactants were mixed with alkylammonium modified bentonite (Cloisite 30B) to generate hybrid compounds covering a wide range of clay/polymer compositions. The structure of these compounds was examined by XRD and cryoTEM, which indicated extensive penetration of the biopolymer into the nanoclay galleries with widening or even destruction of the layered arrangement of the complex and the clay. Simultaneous SAXS/WAXS analysis in real time showed that hybrids with moderate inorganic contents displayed melting/crystallization upon heating/cooling within the 40–70°C interval with concomitant expansion/contraction of the intersheet spacing. 13C CP-MAS NMR revealed that an anti-to-gauche conformational interconversion of the alkyl chains was involved in the melting/crystallization process. The results provided by energy-based dynamical simulations proved the feasibility of the polyacid and the nanoclay to be homogenized in the hybrid due to the compatibilizing effect of the surfactant. [Copyright &y& Elsevier]

Abstract: A cyclic acetal of dimethyl l-tartrate (dimethyl 2,3-di-O-methylene l-threarate, Thx) was used as comonomer of dimethyl terephthalate (DMT) in the polycondensation with 1,6-hexanediol (HD) in the melt. Random copolyesters PHTxThxy with contents in tartrate units up to 50% were obtained with satisfactory molecular weights (M w between 20,000 and 50,000) and dispersities slightly above 2, and without apparent discoloration. The copolyesters started to decompose above 300 °C. The T g of the copolyesters oscillated between +9 and −9 °C with values steadily decreasing with increasing contents in Thx units. All the copolyesters as well as the homopolyester entirely made of tartrate units were semicrystalline with T m falling from ∼145 °C for PHT to ∼70 °C for PHThx with intermediate values decreasing as the content in Thx increased. Copolyesters containing up to 30% of tartrate units were able to crystallize from the melt at crystallization rates that were delayed by the presence of tartrate units. The PHT70Thx30 copolyester displayed significant hydrodegradability when incubated in aqueous buffer and also certain biodegradability when subjected to the action of porcine pancreas lipases. [Copyright &y& Elsevier]

Abstract: Stoichiometric complexes of hyaluronic acid with alkyltrimethylammonium surfactants bearing octadecyl, eicosyl and docosyl groups were prepared by ionic coupling in aqueous solution. The complexes were non soluble in water but soluble in organic solvents. In the solid state they self-assembled in a biphasic layered structure with the alkyl side chains forming a separate phase that melted in the 50–60°C range. They were stable to heating up to above 200°C. [Copyright &y& Elsevier]

Abstract: Poly (β-L-malic acid) (PMLA) is a biodegradable polymer and it has various important applications in the biomedical field. In the present work the structural and spectral characteristics of PMLA have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) using oligomeric approach employing B3LYP with complete relaxation in the potential energy surface using 6-311++G (d, p) basis set. Based on results, we have discussed the correlation between the vibrational modes and the structure of the PMLA. A complete analysis of the experimental infrared and Raman spectra has been reported on the basis of wavenumber of the vibrational bands and potential energy distribution. The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The calculated infrared and the Raman spectra of the polymer based on DFT calculations show reasonable agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: Ionic coupling of both polygalacturonic and alginic acids with alkyltrimethyl ammonium surfactants containing 18, 20 and 22 carbon atoms in the alkyl side chain was conducted in water solution to prepare non-soluble comb-like complexes. These amphiphilic complexes are arranged in a biphasic layered structure with the paraffinic phase made of alkyl side chains alternating with the hydrophilic phase made of polyuronic chains. The complexes displayed the thermal behaviour typical of comb-like systems carrying long polymethylene groups, which melt at temperatures between 40 and 80°C without significant disruption of the layered arrangement. Melting temperature, crystallinity and thermal stability were slightly higher for the polygalacturonic complexes and all they increased almost steadily with the length of the alkyl chain within each series. The melting-crystallization process was followed by combined WAXS/SAXS and 13C CP-MAS NMR, which revealed that the transition involves an expansion-contraction of the structure that may attain up to 20% of the original dimension. The transition takes place without large conformational changes and is not fully reversible. [Copyright &y& Elsevier]

Abstract: Poly (β,l-malic acid) (PMLA) was obtained by Physarum polycephalum. The FT-IR and FT-Raman spectra were recorded experimentally and used for normal mode analysis using Wilson GF matrix method and phonon dispersion of PMLA. The non redundant set of internal coordinate are simplified. Urey-Bradley force field approximation was employed in normal mode analysis and to calculate the potential energy distribution (PED) of each fundamental vibration. Apart from detailed assignment, various characteristic features of dispersion curve have also been explained, arising due to internal symmetry in energy momentum space. Predictive values of the intramolecular contribution to the heat capacity of this polymer calculated by the density of states, are also been reported. The thermal degradation of PMLA was investigated in nitrogen atmosphere by thermogravimetric analysis in combination with DTA and FT-IR. The spectra of gases found in the thermal degradation of PMLA are very much similar to the spectra of gases released during decomposition of fumaric acid. [Copyright &y& Elsevier]

Abstract: The thermal decomposition of poly(γ-glutamic acid), poly(α-methyl γ-glutamate) and ionic complexes of the polyacid with alkyltrimethyl ammonium salts was studied by TGA, GPC, and FTIR and NMR spectroscopies. It was found that both poly(γ-glutamic acid) and poly(α-methyl γ-glutamate) depolymerised above 200°C by unzipping mechanism with generation of pyroglutamic acid and methyl pyroglutamate, respectively. On the other hand, the ionic complexes degraded through a two-stage process, the first stage being cyclodepolymerisation of the poly(γ-glutamate) main chain along with decomposition of the ionic complex promoted by the adsorbed water. Decomposition of the previously generated alkyltrimethyl ammonium compound followed by unspecific cracking of the resulting nitrogenated compounds accounted for the second degradation step, at higher temperatures. Mechanisms explaining the decomposition of the three studied systems were proposed according to collected data. [Copyright &y& Elsevier]

Abstract: Poly(styrene-co-p-tert-butyldimethylsilyloxystyrene) copolymers, P(S/p-TBDMSOS), with contents in the substituted comonomer within the 0–50% range were prepared using combined Ph2Zn–CpTiCl3–MAO initiator systems and some of them were used as precursors of poly(styrene-co-p-hydroxystyrene), P(S/p-HOS), copolymers. p-tert-Butyldimethylsilyloxystyrene was synthesized from p-hydroxybenzaldehyde by protecting the hydroxyl group with tert-butyldimethylchlorosilane and converting the aldehyde group into vinyl through the Wittig reaction. The P(S/p-TBDMSOS) copolymers with contents in substituted units equal or higher than 25% were atactic and those with content higher than 5% were amorphous. P(S/p-HOS) copolymers containing up to 20% of hydroxylated units were obtained by full hydrolysis in acidic medium of the corresponding P(S/p-TBDMSOS). The hydroxylated copolystyrenes displayed crystallinity for the whole range of studied compositions and their crystalline structure was essentially similar to that of s-PS homopolymers. The influence of the substituent on the modified-MAO catalyzed copolymerization and on the thermal properties of the resulting copolymers was comparatively examined. [Copyright &y& Elsevier]

Abstract: High molecular weight poly(α-methyl β,l-malate) (M n ∼25,000, PD∼1.7) was prepared from microbial poly(β,l-malic acid) (M n ∼29,000, PD∼1.3) by methylation with diazomethane in dry acetone without substantial cleavage of the polyester main chain. The thermal properties of this poly(malate) were assessed and its crystal structure was preliminary examined. Two crystal forms were identified by X-ray diffraction, their occurrence being dependent on crystallization conditions. The kinetics of nonisothermal and isothermal crystallizations from the melt were studied and modelled using the Avrami approach. Results were compared to those recently reported by us for low molecular weight poly(α-methyl β,l-malate) (M n ∼3000, PD∼1.3). [Copyright &y& Elsevier]

Abstract: Enzymatic and microbial degradability of poly(ethylene terephthalate) (PET) and PET copolyesters containing 30mol% of either 5-nitroisophthalic units (PET70NI30) or nitroterephthalic units (PET70NT30) was investigated in laboratory cultures. Two commercial fungal lipases, two bacteria from environmental isolates, and two collection filamentous fungi were tested. The topography of the polymer surface exposed to degradation was characterized by interferometry–confocal microscopy techniques. Biodegradation was estimated by optical and electron microscopy observation, and gel permeation chromatography. Evidence of biodegradation including roughness enhancement, swelling and decrease of the weight-average molecular weight, was only obtained for the case of PET70NT30 cultured with Aspergillus niger. Differences in surface textures were found to be crucial to determine the positive response of this copolyester to biodegradation. [Copyright &y& Elsevier]

Abstract: Poly(ethylene terephthalate-co-1,4-cyclohexane dicarboxylate) copolymers, abbreviated as PETCHD, containing from 2 up to 40mole% of the cycloaliphatic diacid, as well as the two parent homopolymers, PET and PECHD, were prepared from comonomer mixtures by a two-step melt-polycondensation procedure. Polymer intrinsic viscosities varied from 0.6 to 0.8dLg−1 with weight-average molecular weights spanning in the range from 30,000 to 70,000. The copolymers were found to have a random microstructure and a composition according to that used in their corresponding feeds. Thermal and mechanical properties of PETCHD were evaluated as a function of composition. Copolymers were found to be crystalline for all examined compositions although they crystallize from the melt only when the cycloaliphatic comonomer composition was below 20mole%. Both melting and glass transition temperatures of the copolyesters decreased rapidly with the content in CHD units, whereas the thermal stability appeared to be barely affected by copolymerization. Incorporation of 1,4-cyclohexane dicarboxylate units increased the Young’s modulus and the maximum tensile strength of these materials but elongation to break drastically diminished. Preliminary X-ray diffraction studies revealed that PETCHD copolyesters seem to adopt the same crystal structure as PET. [Copyright &y& Elsevier]

Abstract: Homopolymerization of α-olefins (1-C n H2n , n =6, 8, 10, 12, 16 and 18) and their copolymerization with styrene were carried out in toluene at 60°C using diphenylzinc–ethenylbisindenylzirconium dichloride–methylaluminoxane as initiator system. Atactic polystyrene and almost isotactic poly(α-olefin)s were obtained. Copolymerization of S/α-olefin with this initiator system gave isotactic olefin-enriched copolymers. According to DSC analysis, the homopolymers P(1-C12H24), P(1-C16H32), and P(1-C18H36) as well their styrene copolymers are crystalline. [Copyright &y& Elsevier]

Abstract: A series of polyamides 6,4 were prepared from 1,6-hexanediamine and active esters of 2,3-di-O-acylated l-tartaric acid by polycondensation in solution. Both O-alkoyl and O-benzoyl esters were used as hydroxyl protecting groups. The resulting acylated polytartaramides were found to be semicrystalline polymers with Tm between 100 and 200°C and T g slightly above 100°C. Controlled hydrolysis of the ester side group led to the preparation of poly(hexamethylene l-tartaramide)s with different content in free hydroxyl groups. These polyamides continue being crystalline but their properties largely differ from those displayed by their parent acylated polymers. [Copyright &y& Elsevier]

Two sets of AA·BB-type polyamides (PLyTA) were synthesized from natural compounds l-lysine and d- or l-tartaric acid via the active ester polycondensation method. The carboxyl and hydroxyl side groups were orthogonally protected as methyl ester and methyl ether, respectively. Direct reaction of methyl l-lysinate dihydrochloride with bis(pentachlorophenyl) di-O-methyl tartaric acid led to the aregic polyamide ar-PLyTA, whereas isoregic (ir-PLyTA) and syndioregic (sr-PLyTA) polyamides were obtained by polycondensation of specifically designed amide–aminoacid and amide–diamine monomeric precursors, respectively. These polyamides have intrinsic viscosities in the 0.50–0.76dlg−1 range, display optical activity, and are readily soluble in chloroform. They start to decompose well above 200°C and display glass-transition temperatures at 100–105°C. DSC and X-ray diffraction results indicated that these polyamides are not crystalline but they seem to adopt a partially ordered phase. No differences in properties other than optical rotation were observed between PLyTA made of d- and l-tartaric acid. [Copyright &y& Elsevier]

A comparative study of the two isophthalic acid deriving homopolyesters poly(ethylene isophthalate) (PEI) and poly(ethylene 5-tert-butyl isophthalate) (PEtBI), including synthesis, crystal structure, and thermal and permeability properties, was carried out. The two polyesters were prepared by condensation polymerization in the melt. In both cases, minor amounts of cyclic dimers were observed to form, which were characterized by nuclear magnetic resonance and mass spectroscopy. PEI and PEtBI were thermally stable up to 400 °C and they appeared to be semicrystalline polyesters, having their melting temperatures between 130 and 135 °C. Their glass-transition temperatures were 62 and 94 °C, respectively. The crystal structure adopted by the two polyesters seemed to consist of a regularly folded conformation, clearly different from the almost extended conformation characteristic of poly(ethylene terephthalate). Gas permeability measurements for N2, O2, and CO2 revealed that PEtBI is more permeable to these gases than PEI, in spite of having a higher Tg. Furthermore, water vapor diffusion was found to be increased by the insertion of the tert-butyl group, whereas water absorption diminished. The differences in gas and water vapor transport properties observed for these two polyesters were discussed on the basis of their respective molecular structures. [Copyright &y& Elsevier]

A series of poly(ethylene terephthalate-co-ethylene 5-sodiosulfoisophthalate) copolyesters containing from 1 up to 50 mol% of sulfonated units was prepared by melt polycondensation from ethylene glycol and mixtures of dimethyl terephthalate and dimethyl 5-sodiosulfoisophthalate. The resulting copolymers had a random microstructure and contained oligo(ethylene glycol) units in amounts increasing with the content in sulfonated isophthalate units. Copolyesters with more than 20 mol% of 5-sodiosulfoisophthalic units were amorphous and easily soluble in water. The hydrodegradability of the copolyesters was very high as compared to poly(ethylene terephthalate), and increased with the content in sulfonated units. It was demonstrated that the susceptibility to acidic hydrolysis of these copolymers is mainly due to the presence of the sodium sulfonate groups, the influence of the oligo(ethylene glycol) units in this regard being noticeable but limited. [Copyright &y& Elsevier]

Reactive blending at 290 °C of a series of mixtures of poly(ethylene terephthalate) (PET) and poly(1,4-butylene succinate) (PBS) led to the formation of block PET/PBS copolyesters. The block lengths of the resulting copolymers decreased with the severity of the treatment. Copolyesters with PET/PBS molar compositions of 90/10, 80/20, 70/30, and 50/50 were prepared by this method and their composition and microstructure were characterized by 1H and 13C NMR, respectively. The Tg, Tm, and crystallinity of the copolymers decreased as the content in PBS and the degree of randomness increased. The elastic modulus and tensile strength of the copolymers decreased with the content of PBS, whereas, on the contrary, the elongation at break increased. The PET/PBS copolymers exhibited a pronounced hydrolytic degradability, which increased with the content in 1,4-butylene succinic units. Hydrolysis mainly occurred on the aliphatic ester groups. [Copyright &y& Elsevier]

Hairy random copoly(β,l-aspartate)s were prepared by anionic ring opening polymerization of mixtures of (S)-4-octadecoxycarbonyl and (S)-4-benzyloxycarbonyl 2-azetidinones at 3:1, 1:1 and 1:3 molar ratios. The three resulting copolymers had molar ratios of octadecyl to benzyl units of 68:32, 44:56 and 12:88, respectively. They all were found to adopt the rigid α-helix-like conformation characteristic of poly(β,l-aspartate)s, but only the first one displayed crystallization of the alkyl side chains. This copolymer showed thermochromic behavior with color changes taking place when heated above the side chain melting temperature. These results evidenced the ability of the benzyl group to be accommodated within the layered structures of comb-like poly(β,l-aspartate)s and to modify the temperature range in which chromatic changes are observed in these systems. [Copyright &y& Elsevier]

The influence of incorporating 5-tert-butyl isophthalic units (tBI) in the polymer chain of poly(ethylene terephthalate) (PET) on the crystallization behavior, crystal structure, and tensile and gas transport properties of this polyester was evaluated. Random poly(ethylene terephthalate-co-5-tert-butyl isophthalate) copolyesters (PETtBI) containing between 5 and 40 mol% of tBI units were examined. Isothermal crystallization studies were performed on amorphous glassy films at 120 °C and on molten samples at 200 °C by means of differential scanning calorimetry. Furthermore, the non-isothermal crystallization behavior of the copolyesters was investigated. It was observed that both crystallinity and crystallization rate of the PETtBI copolyesters tend to decrease largely with the comonomeric content, except for the copolymer containing 5 mol% of tBI units, which crystallized faster than PET. Fiber X-ray diffraction patterns of the semicrystalline PETtBI copolyesters proved that they adopt the same triclinic crystal structure as PET with the comonomeric units being excluded from the crystalline phase. Although PETtBI copolyesters became brittle for higher contents in tBI, the tensile modulus and strength of PET were barely affected by copolymerization. The incorporation of tBI units slightly increased the permeability of PET, but copolymers containing up to 20 mol% of the comonomeric units were still able to present barrier properties. [Copyright &y& Elsevier]