Novel regular network polyester films from aromatic tetracarboxylic acids and ethylene glycol

Novel regular network polyester films were prepared from pyromellitic (X), biphenyltetracarboxylic (U), and 3,3′,4,4′-benzophenonetetracarboxylic (W) dianhydrides and ethylene glycol (2G). Prepolymers prepared by melt polycondensation were cast from DMF solution and successively post-polymerized at 260°C for various times to form a network. The resultant films were transparent, flexible, and insoluble in any solvents. The structure and properties of these network polyester films were compared with those of previously reported network polyester film from trimesic acid (Y) and 2G. Two diffraction peaks appeared in X-ray diffraction curves of 2GY, 2GX, and 2GU films. Peaks of 2GX and 2GU were broader than that of 2GY, suggesting less ordered structure of 2GX and 2GU by the less symmetric aromatic tetracarboxylic acid moieties. Densities of network films decreased with increasing the post-polymerization time. The degree of reaction (the degree of network formation) was estimated by the change of infrared absorption of hydroxyl and methylene groups. The degree of reaction obtained was 95 and 87% for 2GY and 2GX films post-polymerized for 12 h, respectively. Distortion temperature (T_h) was measured by a penetration mode of thermomechanical analysis (TMA). T_h, was 222 and 240°C for 2GY and 2GW films post-polymerized at 260°C for 12 h, respectively, while it disappeared for 2GX and 2GU films post-polymerized for more than 30 min and 1 h, respectively. Drastic decrease in TMA curves around 400°C corresponded to the rapid weight loss in TG curves due to the thermal decomposition. Young's modulus of network film was 2GX > 2GW = 2GU > 2GY, while the tensile strength and elongation were 2GY > 2GU > 2GW > 2GX. Water absorbing capacity was 2GX > 2GY > undrawn PET, while the alkali resistance was undrawn PET = 2GY > 2GX.     

Gamma irradiation of polyester films

Irradiation in air of several thermoplastic aromatic polyesters was carried out in order to investigate changes in characteristic properties. Polymers are irradiated at high doses, until 1 MGy, and no drastic changes seem to emerge. Dielectric and resistance measurements are carried out in order to evaluate changes in electrical insulation property; moreover, nanoholes dimensions, analyzed by positron spectroscopy, are measured in pristine and irradiated polyesters. The study shows good durability of this kind of polyesters, due to the aromatic rings able to stabilize the polymeric chains towards ionizing radiations and able to preserve the original structural, electrical and permeability properties.     

Oligomers of a polyester network

Oligomers of glycerol and succinic acid have been prepared by three different methods and characterised by solution ¹³C-NMR spectroscopy at 125.8 MHz. The first series of five oligomers was prepared by reacting glycerol with succinic anhydride; only one acid function of each succinic acid residue formed an ester by this means. They were readily distinguished as the shifts of their glycerol residues were dispersed over 16 ppm, and their shifts provided a guide to the assignment of shifts in the more elaborate oligomers. The second set of oligomers was prepared by treating glycerol with a small quantity of succinic acid, ester links being promoted by means of the reagent dicyclohexylcarbodiimide (DCCDI). When we used 2 mol of DCCDI/mol of acid in the presence of an excess of glycerol, no free acid functions remained, and a new set of oligomers was obtained. Furthermore, within this set the proportion of ring molecules was enhanced by repeating the reaction under much more dilute conditions. In this way the shifts of two ring oligomers were recognized in the spectrum. A different set of oligomers again was obtained when the esterification was performed with 1 mol of DCCDI/mol of succininic acid. After the first generation of oligomers had been identified in the mixtures produced by these three experiments, the reactions continued to produce larger oligomers with new fine structure features in the spectra. Glycerol trisuccinate was prepared in a pure form and heated in a vacuum to eliminate succinic acid groups and allow the formation of oligomers with two and three branch points. The structures successively produced by this reaction were readily recognized. In all we were able to recognize the formation of component structures in at least 17 different oligomers. The shifts of the carbons of the glycerol residues are sensitive to the substitution pattern at that residue, to whether the succinic acid residue to which they are linked has reacted a second time, and in some cases the methine shift is sensitive to how the succinic acid residue attached to a neighboring methylene carbon has reacted. © 1994 John Wiley & Sons, Inc.     

Atmospheric and soil degradation of aliphatic-aromatic polyester films

The degradation of an aliphatic-aromatic biodegradable polyester film was studied under conditions of solar exposure and soil burial in a tropical area. Film samples were evaluated for changes over 40 weeks by visual examination, scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical properties, molecular weight, gel content, and thermal properties. Photodegradation played a major role in the atmospheric degradation of the film, causing it to lose integrity and mechanical properties after week 8 due to main chain scission and crosslinking. SEM micrographs and FTIR spectra indicated that photodegradation started at the exposed side of the film and propagated through the polymer matrix after week 8. FTIR spectra also indicated that subsequent photooxidation processes took place. The reduction of molecular weight of the soil burial samples was much slower than that of the non-crosslinked portion of solar exposed film samples. The reduction of number average molecular weight of the non-crosslinked solar exposed samples followed a first order reaction, whereas the soil burial samples show a surface erosion biodegradation behavior. The relationship among total solar radiation, gel content and number average molecular weight indicated that an accumulated total solar radiation of 800 MJ/m², reached in approximately 7 weeks at the exposure site, is required for PBAT mulch film integrity loss.     

Surface modification and adhesion improvement of polyester films

Facile surface modification of polyester films was performed via chemical solutions treatment. Surface hydrolysis was carried out by means of sodium hydroxide solutions, leading to the formation of carboxylate groups. Three commercial polyester films of 100 μm in thickness were used in this work: AryLite?, Mylar?, and Teonex?, hydrolysis time being the main modification parameter. FTIR-ATR analysis, topography and contact angle (CA) measurements, surface free energy (SFE) and T-Peel adhesion tests were carried out to characterize the modified films. A quantitative estimate of the carboxylates surface coverage as a function of treatment time was obtained through a supramolecular approach, i.e. the ionic self-assembly of a tetracationic porphyrin chromophore onto the film surface. The surface free energy and critical surface tension of the hydrolyzed polyesters was evaluated by means of Zisman, Saito, Berthelot and Owens-Wendt methods. It was shown that NaOH solution treatment increases roughness, polarity and surface free energy of polymers. As a result, T-Peel strengths for modified Mylar? and Teonex? films were respectively 2.2 and 1.8 times higher than that for the unmodified films, whereas AryLite? adhesion test failed.     

Novel biobased resins from blends of functionalized soybean oil and unsaturated polyester resin

Biobased unsaturated polyester (UPE) materials containing epoxidized methyl soyate (EMS) were processed with cobalt naphthenate as a promoter and 2‐butanone peroxide as an initiator. A certain amount of the UPE resin was replaced by EMS. The combination of the UPE and EMS resulted in an excellent combination for a new biobased thermoset material with a relatively high elastic modulus and a constant glass transition temperature with up to 25 wt % replacement with EMS. The Izod impact strength was almost constant while the amount of EMS was changed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 698–704, 2007     

Non-isothermal crystallization kinetics of hot drawn polyester films

The non-isothermal crystallization kinetics of hot drawn poly(ethylene terephthalate) films were studied using the Kissinger and Ozawa equations. The influence of the initial drawing on the crystallization kinetics was investigated. The values of the apparent activation energy and of the Avrami exponent indicates that the nucleation and growth of crystallites depend greatly on the stress submitted to the samples.     

Studies on the morphology and structure of aromatic polyester films

Oriented films of an aromatic polyester containing a triad ester mesogenic group and a decamethylene flexible spacer were studied by polarized light microscopy, small-angle light scattering, and polarized infrared spectroscopy to determine the nature of the alignment of the polymer chains, induced by shearing, which is responsible for the banded or striped morphology observed. The stripes are apparently composed of fibrils arranged in a zigzag manner containing polymer chains packed in a highly ordered, parallel alignment at an angle of ±26° to the shearing direction.     

Synthesis of regular polypeptides including polyfunctional amino acids

Polypeptides of regular structure with the sequences His-Glu, Ser-Glu, Try-Glu, His-Tyr, and Glu-His have been synthesized by the 2,4,5-trichlorophenyl ester method. Polymerization was carried out in dimethyl sulfoxide and dimethylformamide. The polymers were purified by dialysis against water. In the process of synthesizing the monomers, theα-amino groups of the acids were protected by ortho-nitrophenylsulfenyl (o-NPS-), benzyloxycarbonyl (Z-), and tert-butoxycarbonyl (t-BOC-) groups. The imidazole group of histidine was Z-protected, and the γ-hydroxy group of glutamic acid and the phenolic OH group of tyrosine were benzyl-protected (Bzl-).     

Novel porous polyurethane films

Polyurethane films treated in a two-stage process with aqueous bromine and ammonia solutions underwent significant modifications in crystalline and surface structure as well as in mechanical and physical properties. Bromine was sorbed on the film, and formed several charge transfer complexes with the soft and hard segments of the polyurethane as well as bridges between adjacent chains. In the second stage, ammonia reacted with the sorbed bromine producing gaseous nitrogen and ammonium bromide. The expansion of the gas resulted in a repacking of the polymeric chains and the formation of a porous structure. The bromine concentrations used and the times of contact between the films and the bromine were 0.02–0.06 normal and 1–10 min, respectively. The contact angle of the films decreased, depending on treatment conditions, from 73 to 20. The water vapor permeability increased three-fold. The treatment appeared to bring about a crystallization in the hard as well as in the soft segments of the PU as shown by differential scanning calorimetry measurements. Possible applications of the treated films for wound dressing are discussed. © 1998 John Wiley & Sons, Ltd.     

Pyrene and anthracene dicarboxylic acids as fluorescent brightening comonomers for polyester

Diacids of fused arenes have been prepared for use as covalently bound fluorescent optical brightening agents in condensation polymers. The monomers: dimethyl 1,6‐pyrene dicarboxylate, dimethyl 1,8‐pyrenedicarboxylate, dimethyl 2,7‐pyrenedicarboxylate, 1,8‐bis(2‐carboxybenzoyl)pyrene dimethyl ester, dimethyl 2,6‐anthracenedicarboxylate, dimethyl 2,7‐anthracenedicarboxylate and dimethyl 9,10‐anthracenedicarboxylate are copolymerized with poly(ethylene terephthalate) and their optical properties are assessed. All of the polymers give blue fluorescence, with the copolymer containing dimethyl 1,6‐pyrenedicarboxylate being the brightest. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1291–1301, 2000     

Thermal and mechanical behavior of biodegradable polyester films containing cellulose nanofibers

Journal of Thermal Analysis and Calorimetry - Agricultural waste is a valuable source of advanced materials. Cheap nanocellulose may be obtained from plum shells agricultural residues and further...     

Novel polyelectrolytes with regular structure synthesis,properties and applications

Cationic polyelectrolytes and polymeric betaines with narrow molecular weight distribution as well as block copolymers containing charged and uncharged blocks of different hydrophilicity/hydrophobicity were synthesized by different routes of radical polymerization. The cationic polyelectrolytes were characterized with respect to solution properties and electrolyte behaviour. The block copolymers serve as powerful stabilizers in precipitation and emulsion polymerization processes.     

Synthesis and properties of hyperbranched polyester polyacrylic acids and their metal complexes

New polydentate ligands based on the hyperbranched third generation polyesters containing terminal acrylic acid fragments were synthesized. The ionization and complexation parameters of new compounds in solution were estimated by spectrophotometry and pH-metric titration followed by experimental data processing using mathematical simulation by the CPESSP program. The procedure for the synthesis was proposed. The polynuclear cobalt(II), nickel(II), and copper(II) complexes with polyester polycarboxylates were synthesized.     

Mixed films of polypeptides and fatty acids

Summary Two binary bidimensional systems both composed of an oleic acid fatty substance and a polypeptidic compound: poly--benzyl-L-glutamate, and poly--benzyl-L-aspartate have been studied.It is found that the two components are miscible with one another at the air/water interphase and give ideal solutions, as opposed to what is found with the same polypeptides in myristic and arachidic acid mixtures.

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Zusammenfassung Es werden zwei bidimensionale binäre Systeme, die aus einer fetten Substanz (Ölsäure) und aus einem Polypeptiol (Poly--benzyl-L-glutamat und Poly--benzyl-L-aspartat) zusammengesetzt sind, studiert.Es zeigt sich, daß die beiden Komponenten miteinander an der Grenzfläche H₂O — Luft mischbar sind und das sie ideale Lösungen geben, im Gegensatz zu den gleichen Polypeptiden in Mischung mit Arachinsäure oder Myristinsäure.

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Characterization of UV-cured polyester acrylate films containing acrylate functional polydimethylsiloxane

Acrylate functional polydimethylsiloxane (AF-PDMS) was tested as a reactive additive in UV-curable coating formulations. Pencil hardness, solvent resistance, and gloss of the UV-cured films were measured to study the influence of AF-PDMS content on coating properties. Depth-profile analysis by FTIR-ATR and Raman spectroscopy was also performed to investigate the effect of AF-PDMS on the behavior of film formation during UV curing. The kinetics of photopolymerization were monitored by photo differential scanning calorimetry (photo-DSC). Our results show that AF-PDMS containing coating formulations are very sensitive to oxygen inhibition, so that an inert environment such as nitrogen purging is required to avoid coating defects.     

Surface properties and swelling behaviour of hyperbranched polyester films in aqueous media

Thin films of hydroxyl (POH) and carboxyl (PCOOH) terminated aromatic hyperbranched polyesters (HBPs) were prepared by spin coating on silicon wafers and subsequently annealed above their glass transition temperature (T_g). The surface properties and the swelling behaviour of these films in aqueous buffer solutions were studied as a function of annealing time using contact angle measurements and ellipsometry. Non-annealed films were hydrophilic with surface free energies of 51 mJ/m² for POH and 49 mJ/m² for PCOOH, respectively. The swelling behaviour of the polymer films in buffer solution with pH 7.4 was described in terms of changes of the thickness and effective refractive index of the swollen layer. Under identical conditions a lower water uptake was found for hydroxyl terminated HBPs (POH) which were annealed more then 2 h. The lower water uptake correlates with the surface properties of the films. The annealed films were less hydrophilic. Their surface free energy was 38 mJ/m² independent of the annealing. Films of carboxyl terminated HBPs (PCOOH) showed similar surface properties after annealing. However, these films were unstable under the same conditions in aqueous solutions. Stable PCOOH films were obtained by additional covalent binding to the substrate using an epoxy silane as a coupling agent.