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High molecular weight poly[(butylene succinate)-ran-(ε-caprolactone)] copolyesters (PBS-ran-PCL) were synthesized in a wide composition range and compared with significantly lower molecular weight samples synthesized previously. DSC and WAXS showed that these copolyesters are isodimorphic (i.e., each crystalline phase contains a small amount of the second comonomer) as they able to crystallize in the entire composition range and display a pseudoeutectic point, and their unit cell dimensions are a function of composition. Copolymers close or away from the pseudoeutectic point exhibited a single crystalline phase, i.e., PBS-rich or PCL-rich crystalline phase. At the pseudoeutectic point, both phases can crystallize in double crystalline banded spherulites, as demonstrated by polarized light optical microscopy (PLOM) studies. An increase in molecular weight of the copolyester does not influence Tmand Tcsignificantly, as their values are determined by the randomness of the comonomer distribution. However, crystallinity values are higher for lower Mwcopolymers because of their faster crystallization rate. Copolymers with higher Mwexhibited higher Tgvalues as expected for random copolymers that are characterized by a single phase in the amorphous regions. Therefore, changing composition and molecular weight, a remarkable separate control over Tgand Tmvalues can be achieved in these copolyesters. SAXS results revealed that the lamellar thickness lcdecreases with composition at each side of the eutectic point. Comonomer exclusion limits the length of crystallizable sequences; as a result, the lamellar thickness values do not significantly vary with Mwin the range studied here. At the pseudoeutectic copolyester compositions, the cooling rate determines for both series of samples (low and high Mw) if one or two crystalline phases can develop: only the PCL-rich crystalline phase, only the PBS-rich crystalline phase, or both crystalline phases. This behavior was studied in detail by DSC, in situWAXS/SAXS, and PLOM. Our studies demonstrate that these biodegradable copolymers are versatile materials whose properties can be tuned by composition, molecular weight, and thermal history to better target specific applications.

Nontoxic alkanoylcholine soaps (nACh) were synthesized from choline and fatty acids with numbers of carbons nequal to 12, 14, 16, and 18, the latter including both saturated and 9-cisunsaturated alkanoyl chains. Coupling of nACh with hyaluronic acid (HyA) rendered comblike ionic complexes nACh·HyA that were non-water-soluble. The complexes were thermally stable up to temperatures above 200 °C but readily degraded by water, in particular when hyaluronidases were present in the aqueous medium. In the solid state, these complexes were self-assembled in a biphasic layered structure in which the surfactant and the polysaccharide phases were alternating regularly with a periodicity dependent on the length of the alkanoyl chain. The paraffinic phase was found to be crystallized in saturated complexes with n≥ 14, but only 18ACh·HyA showed reversible melting crystallization when subjected to cyclic heating–cooling treatment. Nanoparticles with diameters in the 50–150 nm range were prepared by ionotropic gelation from unbalanced 18ACh·HyA complexes with surfactant:HyA ratios of 0.5 and 0.25. These nanoparticles were also structured in layers, swelled slowly in water, and shown to be noncytotoxic in in vitroassays against macrophages cells. It was also shown that the anticancer drug doxorubicin was efficiently encapsulated in both films and NPs of 18ACh·HyA, and its release was shown to be almost linear and complete after one day of incubation in physiological medium. The nACh·HyA complexes constitute a highly promising biocompatible/biodegradable platform for the design of systems suitable for drug transport and targeting delivery in anticancer chemotherapy.

Poly(γ-glutamic acid) (PGGA) is an edible polypeptide excreted by certain bacteria that is presently accessible on a semi-industrial scale. Chemically, it is a nylon 4 derivative bearing a carboxylic side group attached to the fourth carbon of the repeating unit. Although this biopolymer is being exploited in the food, agriculture and cosmetic sectors, its use in massive applications as packaging or coating is still unknown mainly due to its instability in wet environments and unsuitability to be processed by common techniques. Chemical modification of PGGA involving esterification or amidation of the carboxylic group is the approach explored the most to obtain materials with potential interest as fibers, films or hydrogels. Electrostatic coupling of PGGA with hydrophobic cationic species may also be profited to generate non-water-soluble stable derivatives. On the other hand, the interest of modified PGGA as a functionalized biomaterial for scaffold and drug delivery has increased incredibly in the last years. This paper summarizes the progress in the methodology available for synthesizing PGGA derivatives, the relevant features of the new materials that are synthesized, and the most outstanding advances achieved in the biomedical field when modified PGGA is used.

Summary:Comb‐like ionic complexes were prepared from polyuronic acids (pectinic and alginic acids) and alkyltrimethylammonium surfactants bearing linear alkyl chains with 18, 20 and 22 carbon atoms. In the condensed state, these complexes were able to self‐assemble in ordered structures which were thermally stable up to ∼200 °C. The complexes were analysed by DSC and WAXS/SAXS and compared to their analogous made from poly(γ‐glutamic acid). They all adopt a biphasic layered structure in which the main chain and the alkyl side chain alternate with a nanometric periodicity. Alkyl side chains were partially crystallized in these complexes and they show reversible melting at temperatures within the 60‐80 °C range depending on the length of the polymethylene segment.

Summary:Stoichiometric complexes of biotechnological poly(γ‐glutamic) acid and poly(β,L‐malic) acid with alkyltrimethylammonium surfactants of long alkyl chains could be readily prepared in aqueous medium. They adopt a biphasic layered structures in which the main chain and the side chain alternate with nanometric periodicity. Alkyl side chains show reversible melting that involves generation of mesophases. Complexes degraded by water by different mechanisms depending on the constitution of the main chain; the polymalic complexes underwent surface erosion whereas the polyglutamic ones degraded in bulk. Erythromycin could be homogenously loaded into the paraffinic subphase of the complexes and delivered upon incubation under physiological conditions in parallel to the hydrolysis of the polymer.

A series of complexes from poly(aspartic acid) and alkyltrimethylammonium bromide surfactants with linear alkyl groups, containing even number of carbon atoms from 12 up to 22 were synthesized. The complexes were obtained in good yields, are soluble in organic solvents and stable up to temperatures near 170 °C. On the other hand, the paraffinic side chains are able to crystallize depending on the length of the surfactant n‐alkyl chain being the main chain of the complexes is arranged in an extended conformation.

Summary:The formation of stereocomplexes from the pair of enantiomorphs of the chiral polyamide poly(hexamethylene di‐O‐methyl tartaramide) was investigated for a variety of experimental conditions. DSC and X‐ray diffraction data evidenced that efficiency in enantiomeric association is highly sensitive to the procedure used for preparing the complex. A comparative isothermal crystallization study revealed that the stereocomplex crystallized from the melt at a rate lower than the enantiomerically pure components. The radial growth of individual spherulites was also delayed in the crystallization of the complex. No evidence of stereocoupling was detected for other poly(alkylene di‐O‐methyl tartaramide)s with the alkylene unit length different from six. It was concluded that molecular interlocking of hydrogen bonds in the enantiomeric pair is highly selective in this family of polymers.

The thermal decomposition of poly(,l-malic acid), poly(-methyl ,l-malate), and ionic complexes of the polyacid with alkyltrimethylammonium salts was studied by TGA, GPC, and FTIR and NMR spectroscopy. It was found that poly(,l-malic acid) depolymerized above 200 °C by an unzipping mechanism with generation of fumaric acid which is then partially converted in a mixture of maleic acid and anhydride. On the contrary, random scission of the main chain was found to happen in the thermal decomposition of poly(-methyl ,l-malate). On the other hand, ionic poly(,l-malate)s degraded through a well defined three-stage process, the first one being depolymerization of the poly(malate) main chain along with decomposition of the ionic complex. Decomposition of the previously generated alkyltrimethylammonium salts followed by unspecific cracking of the resulting nitrogenated compounds happened at higher temperatures. Mechanisms partially explaining the decomposition processes of the three studied systems were proposed according to collected data.

Homopolymerization of disubstituted styrenes (2,4‐ and 2,5‐dimethylstyrene) and trisubstituted styrene (2,4,6‐trimethylstyrene) and their copolymerization with styrene were carried out using diphenylzinc–metallocene–methylaluminoxane initiator systems for metallocene (n‐BuCp)2TiCl2 and for half‐metallocene CpTiCl3. The studied comonomers were found to be less reactive than p‐tertbutylstyrene, p‐methylstyrene and styrene. The results indicate that, even though the methyl group has I+ inductive effect, di‐ and tri‐methylstyrenes are reluctant to undergo either homopolymerization or copolymerization. This behavior suggests that the reactivity is regulated not only by the inductive effect of the alkyl group but also by the steric impediment caused by the crowding of the substituents on the benzene ring. Copyright © 2006 Society of Chemical Industry

Summary: Reaction of active esters of O-protected D-and L-tartaric acid with L-lysine 2,5-diketopiperazine afforded optically active low molecular weight compounds with Tg ≈ 130 °C. 13C NMR results indicated that the condensation product consisted of cyclic oligomers made from 1 to 6 repeating units. Mass spectrometric analysis by MALDI-TOF ascertained such interpretation and suggested a revision of previous work reporting on polymerization of 2,5-diketopiperazines.MALDI-TOF profile of cKT-LL.

The synthesis, characterization, and some properties of new copolyesters of poly(butylene terephthalate) based on l-arabinitol and xylitol are described. These copolyesters were obtained by polycondensation reaction in the melt of mixtures of 1,4-butanediol and 2,3,4-tri-O-methyl-l-arabinitol or 2,3,4-tri-O-methylxylitol with dimethyl terephthalate. Their weight-average molecular weights ranged between 20 000 and 40 000, with polydispersities oscillating from 1.5 to 2.2. All them had a statistical microstructure and were thermally stable well above 300 °C. Copolyesters containing up to 30% of alditol-derived units were found to be crystalline and to adopt the same crystal structure as the parent homopolyester poly(butylene terephthalate). The melting temperature and crystallinity were observed to decrease, and the glass transition temperature to increase, with increasing amounts of alditol incorporated in the copolyester. Crystallizability was depressed by copolymerization, whereas the hydrolytic degradability was significantly enhanced by the presence of alditol units. No relevant differences in either structure or properties were observed between the l-arabinitol and xylitol copolyester series.

The dynamic mechanical thermal properties of a family of poly(α‐alkyl β,L‐aspartate)s bearing various cyclic, linear, and branched alkoxycarbonyl groups in the side chain were studied. The measurements carried out by dynamic mechanical thermal analysis (DMTA) revealed the significant influence of the constitution of the side chain on mechanical relaxation phenomena. Three relaxations were observed, which are referred to as γ, β, and α, in increasing order of temperature. The first two, γ and β, are related to the local and global motions of the side chain, respectively. Relaxation α is related to the motion of the main chain. Relaxation β, which is associated with the rotation of the side chain, is the most intense. The magnitude and temperature at which this relaxation occurs depends on the volume, the length, and the degree of branching of the ester group of the side chain. A comparison between the dynamic mechanical properties of poly(β,L‐aspartate)s and poly(α,L‐glutamate)s revealed that the two methylene groups spacing the ester group from the main chain provides the poly(α‐L‐glutamate)s with greater mobility, and thus, relaxations α and β occur at lower temperatures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 994–1003, 2006

The synthesis and characterization of new aromatic homo‐ and copolyesters based on l‐arabinitol and xylitol are described. These polymers were obtained by polycondensation reaction of the 2,3,4‐tri‐O‐methyl‐l‐arabinitol or 2,3,4‐tri‐O‐methyl‐xylitol, or their mixtures with ethylene glycol, with terephthaloyl chloride or isophthaloyl chloride in o‐dichlorobenzene or in the melt phase from the corresponding methyl phthalates. All the polymers were characterized by GPC, IR, and NMR. Their Mw values ranged between 11,500 and 46,500, with polydispersities from 1.5 to 2.3. They were found to be soluble in chloroform, but insoluble in water. In contrast with the homopolymers completely made with EG, they showed a significant hygroscopicity. DSC and TGA studies showed that the melting temperature of polyethylene terephthalate is depressed by the presence of pentitol units, whereas the thermal stability is kept above 350 °C. Only copolyesters containing 10% or less of pentitol units showed melting and produced X‐ray diffraction patterns characteristic of crystalline material. d‐Arabinitol‐based homopolyesters appeared to be more crystalline than those derived from xylitol and also presented a higher thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6394–6410, 2005

The synthesis and characterization of a new series of aromatic polyesters based on D‐mannitol and galactitol are described. These polyesters were obtained by polycondensation reaction of the terephthaloyl chloride or isophthaloyl chloride and 2,3,4,5‐tetra‐O‐methyl‐D‐mannitol or 2,3,4,5‐tetra‐O‐methyl‐galactitol in o‐dichlorobenzene. All the new polyesters were characterized by elemental analyses, GPC, IR, and NMR. They were soluble in chloroform, but insoluble in water and other polar oxygenated solvents. They showed a notable hygroscopicity, lower for those containing isophthalic units. DSC and X‐ray diffraction studies showed that D‐mannitol‐based polyesters were stiffer and less crystalline than those derived from galactitol, which presented a noticeably lower thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4570–4577, 2005

A series of poly(butylene terephthalate) copolyesters containing 5‐tert‐butyl isophthalate units up to 50 mol %, as well as the homopolyester entirely made of these units, were prepared by polycondensation from a melt. The microstructure of the copolymers was determined by NMR to be random for the whole range of compositions. The effect exerted by the 5‐tert‐butyl isophthalate units on thermal, tensile, and gas transport properties was evaluated. Both the melting temperature (Tm) and crystallinity were found to decrease steadily with copolymerization, whereas the glass‐transition temperature (Tg) increased and the polyesters became more brittle. Permeability and solubility slightly increased with the content in substituted isophthalic units, whereas the diffusion coefficient remained practically constant. For the homopolyester poly(5‐tert‐butyl isophthalate), all these properties were found to deviate significantly from the general trend displayed by copolyesters, suggesting that a different structure in the solid state is likely adopted in this case. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 92–100, 2005

A series of linear polyamides (PnMLM) derived from O-methyl-protected L-malic acid and 1,n-alkanediamines with even n values ranging from 4 to 12 were prepared and fully characterized. L-Malic acid entered in the chain with a random orientation rendering essentially aregic polymers. PnMLM displayed optical rotation consistent with the content of the polymer in malic units, and they all were crystalline with melting points ranging from 158 to 188 °C and glass-transition temperatures varying from 37 to 70 °C. PnMLM appeared to be fairly stable to heat with thermal decomposition starting close to 300 °C. Hydrolytic degradation of PnMLM at 37 °C was slow, but the process was significantly faster at 70 °C. Thermal degradation took place with the formation of cyclic malimides in the residual polymer and released the 1,n-alkanediamine. However, hydrolytic degradation took place in a first stage with the formation of open chains of carboxylic- and amine-ended oligomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1566–1575, 2004

Physical blends of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI), abbreviated PET/PEI (80/20) blends, and of PET and a random poly(ethylene terephthalate-co-isophthalate) copolymer containing 40% ethylene isophthalate (PET60I40), abbreviated PET/PET60I40 (50/50) blends, were melt-mixed at 270°C for different reactive blending times to give a series of copolymers containing 20 mol % of ethylene isophthalic units with different degrees of randomness. ¹³C-NMR spectroscopy precisely determined the microstructure of the blends. The thermal and mechanical properties of the blends were evaluated by DSC and tensile assays, and the obtained results were compared with those obtained for PET and a statistically random PETI copolymer with the same composition. The microstructure of the blends gradually changed from a physical blend into a block copolymer, and finally into a random copolymer with the advance of transreaction time. The melting temperature and enthalpy of the blends decreased with the progress of melt-mixing. Isothermal crystallization studies carried out on molten samples revealed the same trend for the crystallization rate. The effect of reaction time on crystallizability was more pronounced in the case of the PET/PET60I40 (50/50) blends. The Young's modulus of the melt-mixed blends was comparable to that of PET, whereas the maximum tensile stress decreased with respect to that of PET. All blend samples showed a noticeable brittleness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3076–3086, 2003

The solubility of N2 in poly(α-n-hexyl-β,L-aspartate), a stereoregular poly(β-peptide), was investigated with atomistic Monte Carlo simulations. The structure of this material is intermediate between that of polymers able to form a three-dimensional crystal lattice and that of liquid-crystalline polymers with a biphasic distribution. The dependence of the calculated solubility coefficients on both the parameters of the force field and the temperature was examined. The results are compared with recently reported experimental data. Furthermore, the motion of the penetrant molecules within the polymer matrix was analyzed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2928–2936, 2003

Atomistic Monte Carlo (MC) simulations have been used to study a thermally induced phase transition in poly(α‐octadecyl‐β,L‐aspartate). Simulations were performed by using the parallelized version of Configurational Bias MC algorithm adapted to study comblike polymers. A total of 1.15 · 106steps were carried out for a molecular system constituted by 6240 atoms/pseudoatoms. Results were consistent with available experimental observations. The limitations of atomistic simulations to study large length‐scale phenomena are discussed. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 770–778, 2003

Poly(ethylene terephthalate-co-isophthalate-co-5-tert-butylisophthalate) (PETI^tBI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate-co-isophthalate) (PETI) copolymers. Three series of PETI^tBI terpolyesters, characterized by terephthalate contents of 90, 80, and 60 mol %, respectively, with different isophthalate/5-tert-butylisophthalate molar ratios, were prepared from ethylene glycol and mixtures of dimethyl terephthalate, dimethyl isophthalate, and 5-tert-butylisophthalic acid. The composition of the terpolymers and the composition of the feed agreed. All terpolymers had a random microstructure and number-average molecular weights ranging from 10,000 to 20,000. The PETI^tBI terpolyesters displayed a higher glass-transition temperature and a lower melting temperature than the PETI copolymers having the same content of terephthalic units. Thermal stability appeared essentially unchanged upon the incorporation of the 5-tert-butylisophthalic units. The PETI^tBIs were crystalline for terephthalate contents higher than 80 mol %, and they crystallized at lower rates than PETI. The crystal structure of the crystalline terpolymers was the same as that of PET with the 1,3-phenylene units being excluded from the crystalline phase. Incorporation of isophthalate comonomers barely affected the tensile modulus and strength of PET, but the brittleness of the terpolymers decreased for higher contents in 5-tert-butylisophthalic units. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 124–134, 2003

Lamellar crystals of nylon 6,8 and nylon 8,10 with chains in a fully extended conformation were obtained by crystallization in solution, and examined by electron and X-ray diffraction. The same crystal structure appeared to be shared by both nylons crystallized in glycerin. This structure consisted of a mixture of α- and β-forms with features similar to that previously described for lamellar crystals of nylon 4,6 grown in the same solvent. Crystallization of nylon 8,10 in hexane-2,5-diol afforded lamellar crystals with sheets stacked in the β-form. A comparative energy evaluation of the different models that are feasible for the crystal structure of these nylons with fully extended chains indicated very small energy differences among them. The presence of different chain arrangements in the same lamellar crystal, as well as the crystallization of the same nylon in different crystal forms upon slight modification of the crystallization conditions, are fully consistent, therefore, with the results obtained in the energy analysis. Nylon 8,10 crystals grown in hexane-2,5-diol at 150 °C. Inset: The respective electron diffraction patterns.

The effect of incorporating a nitro side group into the phenylene units of poly(ethylene terephthalate) (PET) on the conformation and crystallizability of this polyester was evaluated. Random poly(ethylene terephthalate-co-nitroterephthalate) (PETNT) copolymers containing 5, 10, and 15 mol % nitroterephthalic units were investigated with reference to PET. All the examined copolymers were semicrystalline and were found to adopt the triclinic crystal structure of PET, with the nitrated units being excluded from the crystallites. Both the crystallinity and crystallization rate of PETNT largely decreased with the content of nitrated units, and the O&bond;CH2&bond;CH2&bond;O trans-to-gauche conformational ratio increased with crystallization, attaining comparable values for all the compositions. The conformation and crystallinity of isothermally crystallized PET and PETNT samples could be correlated with the size of the crystallites generated in each case. However, a different crystal perfecting mechanism seemed to operate for PET and for the PETNT copolymers when they were subjected to annealing. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2759–2771, 2002

Poly(ethylene terephthalate) copolymers (abbreviated PEBEPT) containing 2-butyl-2-ethyl-1,3-propanediol (BEPD) for the whole range of compositions were prepared by bulk polycondensation of either terephthalic acid or dimethyl terephthalate as the diacid monomer with mixtures of ethylene glycol and BEPD. Polymer intrinsic viscosities varied from 0.4 to 0.8 dL/g with weight-average molecular weights oscillating between 25,000 and 90,000. All the copolymers were found to have an almost ideal random microstructure. Melting and glass-transition temperatures of the PEBEPTs decreased with the content in BEPD, whereas their thermal stability was barely affected by composition. The crystallinity and isothermal crystallization rate of the PEBEPTs rapidly decreased with the incorporation of BEPD. X-ray diffraction revealed that the triclinic crystal structure of PET was retained in the copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1077–1086, 2002

A new procedure for the preparation of poly(α‐alkyl β,L‐aspartate)s based on the transesterification of polyα‐benzyl β,L‐aspartate) with alcohols in the presence of titanium tetrabutoxide is described. The reaction proceeded to almost total conversion without substantial racemization or imidation. Thermal properties of the resulting polymers were comparable to those of their homologues obtained by anionic ring‐opening polymerization of β‐lactams and their thermal stability is even higher.

Monte Carlo (MC) simulations have been used to study the crystal structure of isotactic poly(4-methyl-1-pentene). Four different tetragonal packing models, each one containing two right-handed and two left-handed 7/2 helices, have been considered in an investigation of the up-and-down chain statistical disorder proposed on the basis of X-ray data. Simulations have been performed with the isotropic united-atom parameterization of the AMBER force field. The influence on the more stable packing models of the force-field parameterization has been investigated with respect to the anisotropic united-atom and all-atom models. Results reveal that packing consisting of two upward and two downward helices arranged at random is more stable than packing with three or four helices with the same sense. Furthermore, the fiber period length for the 7/2 helix is predicted to be 0.56 &Angs; larger than that experimentally determined. The microstructures generated from MC simulations have been employed to study the solubility of gas molecules (He, H2, Ar, O2, CH4, and CO2) with Widom's test-particle insertion method. Special attention has been paid to the solubility of CH4 and CO2 because experimental data are available for these penetrants, the latter being described by both spherical and explicit models. The results are in good agreement with experimental measures only when a suitable model is used for the penetrant. The solubility of gas molecules in crystalline poly(4-methyl-1-pentene) has been correlated with that measured for the crystal phases of other helical polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2037–2049, 2002

The methanolytic degradation of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units was investigated. Random poly(ethylene terephthalate-co-nitroterephthalate) copolyesters (PETNT) containing 15 and 30 mol % nitrated units were prepared from ethylene glycol and a mixture of dimethyl terephthalate and dimethyl nitroterephthalate. A detailed study of the influence of the nitro group on the methanolytic degradation rate of the nitrated bis(2-hydroxyethyl) nitroterephthalate (BHENT) model compound in comparison with the nonnitrated bis(2-hydroxyethyl) terephthalate (BHET) model compound was carried out. The kinetics of the methanolysis of BHENT and BHET were evaluated with high-performance liquid chromatography and ¹H NMR spectroscopy. BHENT appeared to be much more reactive than BHET. The methanolytic degradation of PET and PETNT copolyesters at 80 °C was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, and ¹H and ¹³C NMR spectroscopy. The copolyesters degraded faster than PET, and the degradation increased with the content of nitrated units and occurred preferentially by cleavage of the ester groups placed at the meta position of the nitro group in the nitrated units. For both PET and PETNT copolyesters, an increase in crystallinity accompanied methanolysis. A surface degradation mechanism entailing solubilization of the fragmented polymer and consequent loss of mass was found to operate in the methanolysis of the copolyesters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2276–2285, 2002

We present a molecular dynamics simulation at 300 K in explicit solvent environment of chloroform of the stoichiometric complex formed by poly(α,L-glutamate) and octyltrimethylammonium ions. We observed that the α-helix conformation of the polypeptide chain remains stable during a 2-ns run. The surfactant ions predominantly adopted an extended conformation that is stabilized by favorable interactions with the organic solvent. Analysis of the organization of the surfactant with respect to the polypeptide chain indicated that each octyltrimethylammonium cation was preferentially bound to more than one carboxylate group. It was found that the most populated arrangement was that with the surfactant cations interacting with two carboxylate groups simultaneously. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 151–162, 2002; DOI 10.1002/bip.10016

The methanolysis of poly(ethylene terephthalate) (PET) copolymers containing 5-nitroisophthalic units was investigated. Random copolyesters containing 10 and 30 mol % of such units were prepared via a two-step melt copolycondensation of bis(2-hydroxyethyl) terephthalate (BHET) and bis(2-hydroxyethyl) 5-nitroisophthalate (BHENI) in the presence of tetrabutyl titanate as a catalyst. First, the susceptibility of these two comonomers toward methanolysis was evaluated, and their reaction rates were estimated with high-performance liquid chromatography. BHENI appeared to be much more reactive than both BHET and bis(2-hydroxyethyl) isophthalate. The methanolysis of PET and the copolyesters was carried out at 100 °C, and the degradation process was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, and ¹H and ¹³C NMR spectroscopy. The copolyesters degraded faster than PET, and the rate of degradation increased with the content of nitrated units. The products resulting from methanolysis were concluded to be dimethyl terephthalate, dimethyl 5-nitroisophthalate, ethylene glycol, and small, soluble oligomers. For both PET and the copolyesters, an increase in crystallinity was observed during the degradation process, indicating that methanolysis preferentially occurred in the amorphous phase. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 76–87, 2002

Water-soluble poly(γ-glutamic acid) (PGGA) esters were prepared by transesterification of poly(α-methyl-γ-glutamate) with mono-, di-, and triethylene glycols with one hydroxyl end group blocked as methyl ether. Only the monoglycol appeared to be crystalline with melting at 160°C, and glass-transition temperatures were found to increase from 10 to 60°C with the length of the oxyethylene side chain. All these poly(γ-glutamate)s are stable up to temperatures near 250°C. Moisture sorption, surface wettability, and hydrodegradability were evaluated as a function of time. It was found that in overall sensitivity to water increased with the glycol chain length but the behavior at short contact times was critically affected by conformational factors. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2027–2036, 2001

Novel poly(ethylene terephthalate) (PET) copolyesters, abbreviated PEDMBT, containing optically active (2S,3S)-2,3-dimethoxy-1,4-butanediol (DMBD) as the second comonomer were investigated. Copolymers with ethylene glycol to DMBD ratios between 95/5 and 50/50 as well as the two parent homopolymers, PET and PDMBT, were prepared by a two-step melt polycondensation. The resulting copolymers were found to approximately have the composition of the polymerization reaction feed and a random microstructure. Polymer intrinsic viscosities varied from 0.4 to 0.6 dL g⁻¹ with weight-average molecular weights ranging from 16,000 to 44,000. PEDMBT copolyesters were distinguished in being much more soluble than PET and showing an increasing affinity for water with the content in dimethoxy groups. According to the asymmetric constitution of DMBD, they displayed optical activity in solution. Both melting and glass-transition temperatures of the copolyesters were observed to steadily decrease with the content in DMBD. PEDMBTs were found to be crystalline for contents in DMBD up to 30 mol %. Both powder and fiber X-ray diffraction revealed that the same crystalline structure is shared by PET and the crystalline copolyesters. The homopolyester PDMBT resulted in becoming a polymer with a crystallinity comparable to PET but with a significantly different crystalline structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3250–3262, 2001

The microstructure and crystallization behavior of a set of poly(ethylene terephthalate-co-5-nitroisophthalate) copolymers (PETNI) containing 5-nitroisophthalic units in the 10–50 mol % range were examined and compared to those of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate-co-isophthalate) (PETI) copolymers. A ¹³C NMR analysis of PETNI copolymers in a trifluoroacetic acid solution indicates that they are random copolymers with average sequence lengths in accordance with ideal polycondensation statistics. Differential scanning calorimetry (DSC) studies show that PETNI containing 5-nitroisophthalic units up to 20 mol % are able to crystallize and that crystallization takes place in these copolymers at much slower rates than in PET. Wide-angle X-ray diffraction from powder and fibers reveals that crystallizable PETNI adopts the same triclinic crystal structure as PET, with the nitroisophthalate units being excluded from crystallites. Fourier transform infrared in combination with cross-polarization/magic-angle spinning ¹³C NMR spectroscopy demonstrates the occurrence of a gauche–trans conversion encompassing the crystallization process. A correlation between DSC and spectroscopic data leads us to conclude that the content of trans conformer in the noncrystallized phase of PETNI is higher than in both PET and PETI copolymers and suggests that secondary crystallization in the homopolymer must proceed by a mechanism different than that in copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1553–1564, 2001

Poly(ethylene terephthalate-co-5-tert-butyl isophthalate) copolymers, abbreviated as PET^tBI, with compositions ranging between 95/5 and 25/75, as well as the two parent homopolymers, PET and PE^tBI, were prepared from comonomer mixtures by a two-step melt-polycondensation. Polymer intrinsic viscosities varied from 0.4 to 0.7 dL g⁻¹ with weight-average molecular weights ranging between 31,000 and 80,000. The copolymers were found to have a random microstructure with a composition according to that used in the corresponding feed. The melting temperature and crystallinity of PET^tBI decreased with the content in 5-tert-butyl isophthalic units, whereas the glass-transition temperature increased from 82 °C for PET up to 99 °C for PE^tBI. Copolymerization slightly improved the thermal stability of PET. Preliminary X-ray diffraction studies revealed that PET^tBI adopt the same crystal structure as PET with the alkylated isophthalic units probably excluded from the crystal lattice. The homopolymer PE^tBI appeared to be a highly crystalline polymer taking up a crystal structure clearly different from that of PET and PET^tBI copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 1994–2004, 2001

The structure and thermal properties of the phase B of poly(α-alkyl-β-L-aspartate)s, abbreviated PAALA-n (n being the number of carbon atoms in the linear alkyl side chain), with n = 14 and 16 were determined using X-ray diffraction and DSC methods, respectively. These data together with those previously reported by us for the dodecyl derivative were used to perform Monte Carlo simulations of these comb-like polymers. The results allowed to predict the solubility of different gases in the phase B of PAALA-n. The variation of both the unoccupied space and the excess chemical potential with the size of the penetrant were computed. An attractive interaction between the polymer matrix and the penetrants was found when small gases were considered. The results have been compared with those recently obtained for crystalline poly(α-alkyl-β-L-aspartate)s bearing short linear alkyl side chains.

We present a molecular dynamics study of the helical conformation of the naturally occurring poly(γ-D-glutamic acid) in the un-ionized state. The study was conducted in both aqueous solution and gas-phase considering a 20 residue polypeptide. The results indicated that the left-handed helix with 19-membered ring hydrogen bonds set between the CO of the amide group i and the NH of amide group i + 3 is very stable in aqueous solution. This conformation was recently proposed for this poly(γ-amino acid) from a conformational search study. A detailed picture of the most relevant structural details of the helical conformation of poly(γ-D-glutamic acid) is provided.

We present a molecular dynamics study of the helical conformation of the naturally occurring poly(γ‐D‐glutamic acid) in the un‐ionized state. The study was conducted in both aqueous solution and gas‐phase considering a 20 residue polypeptide. The results indicated that the left‐handed helix with 19‐membered ring hydrogen bonds set between the CO of the amide group iand the NH of amide group i+ 3 is very stable in aqueous solution. This conformation was recently proposed for this poly(γ‐amino acid) from a conformational search study. A detailed picture of the most relevant structural details of the helical conformation of poly(γ‐D‐glutamic acid) is provided.

The synthesis, microstructure, and thermal behavior of a series of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units are described. These novel copolyesters were synthesized by transesterification followed by melt copolycondensation of dimethyl terephthalate and dimethyl nitroterephthalate mixtures with ethylene glycol. The molar ratio of the two comonomers in the feed varied from 95/5 to 25/75. Furthermore, PET and poly(ethylene nitroterephthalate) homopolymers were synthesized with the same method and comparatively studied. Copolyester compositions were practically the same as in the feed, and weight-average molecular weights ranged from 10,000 to 60,000. The two monomeric units were randomly distributed along the polymer chain, and the experimentally determined average sequence lengths were in accordance with ideal copolycondensation statistics. Melting temperatures and enthalpies of the copolyesters decreased with increasing content in nitroterephthalic units, and they all showed a single glass-transition temperature superior to that of PET. They appeared to be stable up to 300 °C, and thermal degradation occurred in two well-differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3761–3770, 2000

A series of aregic poly(ester amide)s (a-PEAT6) with ester/amide ratios (a : b) varying from 1 : 19 to 1 : 2 were prepared with L-tartaric acid, 6-aminohexanol, and 1,6 hexanediamine as the starting materials. Polycondensation in a solution of the diamine with mixtures of pentachlorophenyl-activated di-O-methyl-L-tartaric and 6-aminohexyl-di-O-methyl-L-tartaric acids led to a-PEAT6(a : b), with the a : b ratio determined by the composition of the feed. The newly synthesized poly(ester amide)s were characterized by elemental analysis, size exclusion chromatography, and IR and NMR spectroscopy. They had number-average molecular weights between 25,000 and 45,000 and were highly crystalline, showing melting temperatures ranging from 100 to 230 °C and glass-transition temperatures oscillating between 50 and 100 °C. The thermal degradation of a-PEAT6(a : b) began above 200 °C and concluded with a final weight loss between 60 and 90% of the initial mass. The process evolved with the formation of cyclic tartarimide units and extensive main-chain scissions. The degradation mechanism is discussed in relation to the chemical composition and microstructure of the polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2687–2696, 2000

Poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers, abbreviated as PETNI, were synthesized via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate and bis(2‐hydroxyethyl) 5‐nitroisophthalate mixtures with molar ratios of these two comonomers varying from 95/5 to 50/50. Polymerization reactions were carried out at temperatures between 200 and 270 °C in the presence of tetrabutyl titanate as a catalyst. The copolyesters were characterized by solution viscosity, GPC, FTIR, and NMR spectroscopy. They were found to be random copolymers and to have a comonomer composition in accordance with that used in the corresponding feed. The copolyesters became less crystalline and showed a steady decay in the melting temperature as the content in 5‐nitroisophthalic units increased. They all showed glass‐transition temperatures superior to that of PET with the maximum value at 85 °C being observed for the 50/50 composition. PETNI copolyesters appeared stable up to 300 °C and thermal degradation was found to occur in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1934–1942, 2000 Novel nitro‐containing PET copolyesters were prepared by melt polycondensation for a wide range of compositions and weight‐average molecular weights up to ∼25,000. The crystallinity and Tmof the copolymers decrease with the content in 5‐nitroisophthalic units, whereas Tgis observed to vary in the opposite sense. They are thermally stable up to temperatures well above 300 °C.

A detailed electron microscopy study of the structure and morphology of lamellar crystals of nylon 46 obtained by crystallization from solution has been carried out. Electron diffraction of crystals supported by X-ray diffraction of their sediments revealed that they consist of a twinned crystal lattice made of hydrogen-bonded sheets separated 0.376 nm and shifted along the a-axis (H-bond direction) with a shearing angle of 65°. The interchain distance within the sheets is 0.482 nm. These parameters are similar to those previously described for nylon 46 lamellar crystals grown at lower temperatures. A combined energy calculation and modeling simulation analysis of all possible arrangements for the crystal-packing of nylon 46 chains, in fully extended conformation, was performed. Molecular mechanics calculations showed very small energy differences between α (alternating intersheet shearing) and β (progressive intersheet shearing) structures with energy minima for successive sheets sheared at approximately 1/6 c and 1/3 c. A mixed lattice composed of a statistical array of α and β structures with such sheet displacements was found to be fully compatible with experimental data and most appropriate to describe nylon 46 lamellar crystals. Annealing of the crystals at temperatures closely below the Brill transition induced enrichment in β structure and increased chain-folding order. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 41–52, 2000

A study of the production of poly(γ-glutamic acid) (PGGA) by Bacillus licheniformis NCIMB 11709 grown on medium E in shake flasks at 30°C is reported. The enantiomeric composition of PGGA was found to be highly sensitive to the concentration of Mn⁺⁺, especially when the ion is present in small amounts ( 20 μM). Polymers with D-unit contents ranging from 10 to 90 % and Mw between 0.4 and 2.0 million g mol⁻¹ were obtained for [Mn⁺⁺] ranging from 0 to 1230 μM. Ultrasonic degradation was proven to be an effective method to reduce both the molecular weight and the polydispersity of naturally produced PGGA without disturbing the chemical constitution of the polymer. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 110–115, 1999.

Two heterotelechelic poly(ethylene glycol)s were synthezised by end group modification of α-hydro-ω-hydroxy-poly(oxyethylene) (PEG). The first reaction route starts from heterobifunctional α-hydro-ω-octadecanoyloxy-poly(oxyethylene) (400) and comprises the synthesis of α-hydro-ω-carboxymethoxy-poly(oxyethylene). The second pathway starts from homotelechelic PEG(400) and leads to α-(2-propenyl)-ω-carboxymethylthio-poly(oxyethylene). Purification of the desired products was accomplished by means of ion exchange chromatography on DEAE Sephadex. PEG derivatives were characterized by means of NMR, IR, HPLC and GPC. MALDI-TOF-MS recorded in the reflectron mode served as a fine method that provides information on chemical composition as well as molecular weight.

Two heterotelechelic poly(ethylene glycol)s were synthezised by end group modification of α-hydro-ω-hydroxy-poly(oxyethylene) (PEG). The first reaction route starts from heterobifunctional α-hydro-ω-octadecanoyloxy-poly(oxyethylene) (400) and comprises the synthesis of α-hydro-ω-carboxymethoxy-poly(oxyethylene). The second pathway starts from homotelechelic PEG(400) and leads to α-(2-propenyl)-ω-carboxymethylthio-poly(oxyethylene). Purification of the desired products was accomplished by means of ion exchange chromatography on DEAE Sephadex. PEG derivatives were characterized by means of NMR, IR, HPLC and GPC. MALDI-TOF-MS recorded in the reflectron mode served as a fine method that provides information on chemical composition as well as molecular weight.

This paper reviews the state of the art in the field of the hydrolytic degradation of poly(ethylene terephthalate) (PET) under bio‐environmental conditions. Most of the papers published so far on this subject have been focused on the hydrolysis of PET at high temperatures. Although some authors claim to enhance the biodegradation properties of this aromatic polyester by copolymerization with readily hydrolysable aliphatic polyesters, no clear and satisfying conclusions can yet be formulated. Poly(ethylene terephthalate‐co‐lactic acid), poly(ethylene terephthalate‐co‐ethylene glycol), and poly(ethylene terephthalate‐co‐ɛ‐caprolactone) block and random copolymers are the modifications mainly investigated for biodegradable applications. The hydrodegradability and biodegradability of PET, PET copolymers and PET blends are detailed in this review. A total of 89 references including 16 patents are cited.© 1999 Society of Chemical Industry