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A set of linear polyurethanes containing isosorbide units were synthesized by polymerization in solution from HDI and MDI diisocyanates and 1,4-butanediol (BD), isosorbide (Is) or diisosorbide diurethanes (Is2HDI and Is2MDI) as diols. The thermal transitions, thermal stability, and crystal structure of the polyurethane homopolymers and copolymers containing isosorbide were evaluated and compared with those displayed by their polyurethane analogues entirely made of BD. It was found that incorporation of Is units in the polyurethane chain produced significant changes in T g, T m, and T d but no significant differences were noticed between copolymers made from Is or Is2 monomers. Degradation assays revealed that the presence of Is units increased slightly the hydrolysis rate of polyurethanes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

A set of polyurethanes containing isosorbide units were synthesized by polymerization in solution from HDI and MDI diisocyanates and 1,4-butanediol (BD), isosorbide (Is) or diisosorbide diurethanes (Is2HDI and Is2MDI) as diols. The thermal properties and stability, and crystal structure of the polyurethane homopolymers and copolymers containing isosorbide were evaluated and compared with those of the polyurethane analogues entirely made of BD. Incorporation of isosorbide produced significant changes in Tg, Tm and Td but no noteworthy differences were found between copolymers made from Is or Is2 monomers. Degradation assays revealed that incorporation of Is units increased slightly the hydrolysis rate. [ABSTRACT FROM AUTHOR]

The article presents a study which prepared a series of poly(ethylene terephthalate-co-isophthalate) copolymers with up to 50 percent mole of isophthalic units by polycondensation from ethylene terephthalate and ethylene isophthalate fractions of linear oligomers. Carbon-nuclear magnetic resonance (C-NMR) examined the microstructure of the copolyesters as a function of reaction time. It was found that the crystallization rate of copolyesters decreased with the content in isophthalic units.

The enzymatic ring-opening copolymerization (eROP) of globalide (Gl) and pentadecalactone (PDL) was performed in solution from mixtures of the two macrolactones at ratios covering the whole range of comonomeric compositions. The resulting P(Glx-r-PDLy) random copolyesters were aminofunctionalized by thiol-ene reaction with aminoethanethiol. ROP of γ-benzyl-l-glutamate N-carboxyanhydride initiated by P(Glx-r-PDLy)-NH2 provided neutral poly(γ-benzyl-l-glutamate)-grafted copolyesters, which were converted by hydrolysis into negatively charged hybrid copolymers. Both water-soluble and nonsoluble copolymers were produced depending on copolymer charge and their grafting degree, and their capacity for self-assembling in nano-objects were comparatively examined. The emulsion solvent-evaporation technique applied to the chloroform-soluble copolymers grafted with benzyl glutamate rendered well-delineated spherical nanoparticles with an average diameter of 200–300 nm. Conversely, micellar solutions in water were produced from copolyesters bearing grafted chains composed of at least 10 units of glutamic acid in the free form. The copolymer micelles were shown to be able to load doxorubicin (DOX) efficiently through electrostatic interactions and also to release the drug at a rate that was markedly pH dependent. [ABSTRACT FROM AUTHOR]

Block and graft poly(macrolactone)‐poly(α‐amino acid) copolymers made of l‐alanine and pentadecalactone or globalide respectively, are prepared. A sequential ring‐opening polymerization (ROP) copolymerization route consisting of two stages, the first devoted to the preparation of the amino‐functionalized poly(macrolactone) and the second to the amino‐initiated polymerization of l‐alanine N‐carboxyanhydride (Ala‐NCA), is followed for the synthesis of both types of copolymers. Poly(l‐alanine) segment lengths are accurately controlled by adjusting the macroitiator/Ala‐NCA ratio used for reaction in the second stage. Block copolymers are semicrystalline with the poly(pentadecalactone) block crystallizes well in a separate phase and the poly(α‐amino acid) block arranged in either the α‐helical or β‐sheet structure in a ratio that is depending on composition and temperature. Graft copolymers are amorphous but with the poly(α‐amino acid) side chains arranged in a more or less regular conformation. Nanoparticles with a diameter of around 300 nm and moderate positive Z‐potential can be obtained from the block copolymers by self‐assembling in water whereas graft copolymers are unable to render recognizable objects of nanometer‐dimension under similar conditions. [ABSTRACT FROM AUTHOR]

• 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]

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]

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]

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]

New copolyesters derived from poly(β,L-malic acid) have been designed to serve as nanoconjugate platforms in drug delivery. 25% and 50% methylated derivatives (coPMLA-Me25H75 and coPMLA-Me50H50) with absolute molecular weights of 32 600 Da and 33 100 Da, hydrodynamic diameters of 3.0 nm and 5.2 nm and zeta potential of −15mV and −8.25mV, respectively, were found to destabilize membranes of liposomes at pH 5.0 and pH 7.5 at concentrations above 0.05mg/mL. The copolymers were soluble in PBS (half life of 40 hours) and in human plasma (half life of 15 hours) but they showed tendency to aggregate at high levels of methylation. Fluorescence-labeled copolymers were internalized into MDA-MB-231 breast cancer cells with increased efficiency for the higher methylated copolymer. Viability of cultured brain and breast cancer cell lines indicated moderate toxicity that increased with methylation. The conclusion of the present work is that partially methylated poly(β,L-malic acid) copolyesters are suitable as nanoconjugate platforms for drug delivery. [ABSTRACT FROM AUTHOR]

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: 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]

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]