Abstract: A critical review: the ring-opening polymerization of cyclic esters provides access to an array of biodegradable, bioassimilable and renewable polymeric materials. Building these aliphatic polyester polymers into larger macromolecular frameworks provides further control over polymer characteristics and opens up unique applications. Polymer stars, where multiple arms radiate from a single core molecule, have found particular utility in the areas of drug delivery and nanotechnology. A challenge in this field is in understanding the impact of altering synthetic variables on polymer properties. We review the synthesis and characterization of aliphatic polyester polymer stars, focusing on polymers originating from lactide, e-caprolactone, glycolide, β-butyrolactone and trimethylene carbonate monomers and their copolymers including coverage of polyester miktoarm star copolymers. These macromolecular materials are further categorized by core molecules, catalysts employed, self-assembly and degradation properties and the resulting fields of application (262 references).

Abstract: Novel polyesters from renewable resources based on 2,5-dicarboxylic acid and several diols were synthesized and characterized using different polycondensation techniques. The aliphatic diols were sufficiently volatile to allow the use of polytransesterifications, which gave high-molecular weight semicrystalline materials with good thermal stability. In particular, the polyester based on ethylene glycol displayed properties comparable with those of its aromatic counterpart, poly(ethylene terephthalate), namely, the most important industrial polyester. The use of isosorbide gave rise to amorphous polymers with very stiff chains and hence a high glass transition temperature and an enhanced thermal stability. The interfacial polycondensation between the acid dichloride and hydroquinone produced a semicrystalline material with features similar to those of entirely aromatic polyesters, characterized essentially by the absence of melting and poor solubility, both associated with their remarkable chain rigidity. The replacement of hydroquinone with the corresponding benzylic diol was sufficient to provide a more tractable polyester. This study provided ample evidence in favor of the exploitation of furan monomers as renewable alternatives to fossil-based aromatic homologs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Abstract: We report the ring-opening copolymerization of maleic anhydride with a variety of epoxides catalyzed by a chromium(III) salen complex. Quantitative isomerization of the cis-maleate form of all polymers affords the trans-fumarate analogues. Addition of chain transfer reagents yields low Mn, narrow PDI polymer samples. This method provides access to a range of new unsaturated polyesters with versatile functionality, as well as the first synthesis of high molecular weight poly(propylene fumarate).

Abstract: Natural vegetable oils have been transformed in polymers following three main routes. The first is the direct polymerization through the double bonds of the fatty acid chain. The cationic copolymerization of soybean oil with styrene, divinylbenzene, and different amounts of styrenic monomers containing Si allows producing materials with improved mechanical and flame retardant properties. The second route is the functionalization of the triglyceride double bonds to introduce readily polymerizable groups: The singlet oxygen photoperoxidation-dehydration of the allylic positions of the high oleic sunflower oil allows producing enone-containing triglycerides that are chemically crosslinked with aromatic diamines through aza-Michael reactions. At high temperatures, this curing reaction proceeds through a complex mechanism leading to quinoline moieties. This new crosslinking approach can be also applied to aldehyde containing triglycerides. The third route consists of using plant oil-derived chemicals like 10-undecenoic acid to produce tailor made monomers. Acyclic diene metathesis polymerization has been applied to allyl 10-undecenoate, 10-[2',5'-bis(10-undecenoyloxy)phenyl]-9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide, and 1,3-bis(10-undecenoyl)glycerol to prepare a set of polyesters with different phosphorus and hydroxyl contents. Moreover thiol-ene "click" coupling of allyl 10-undecenoate with mercaptoethanol, 3-mercaptopropanoic acid, and 3-mercaptopropyltrimethoxysilane has been used to produce difunctional telechelic polyesters.

Abstract: The basic scheme for autooxidation of polymers, originally developed by Bolland, Gee and co-workers for rubbers and lipids, is now widely applied to all types of polymeric materials. According to their scheme, the reaction that makes this process autocatalytic, referred to as the propagation step, is a hydrogen abstraction from the next substrate by the peroxyl radical (ROO˙ + RH → ROOH + R˙). In this study, using advanced quantum-chemical methods, we have shown that this step is actually characterised by largely positive Gibbs free energy (10–65 kJ mol−1) for most regular polymers with saturated chains (polypropylene, polyethylene, polyvinyl chloride, polyvinyl acetate, polyurethane, poly(methyl methacrylate)etc.) and even some polymers with unsaturated fragments (polystyrene, polyethylene terephthalate). Neither elevated temperature, nor solvation makes this process thermodynamically favourable. Only when the formed radical centre is conjugated with adjacent double bonds (as in polybutadiene) or captodatively stabilised by two suitable functional groups (such as a carbonyl and a lone pair donor such as oxygen or nitrogen), is the propagation step exoergic. Instead, we show that it is the presence of structural defects, such as terminal or internal double bonds, formed either during polymerisation or in the degradation process itself, that is responsible for the autooxidation of most polyesters and most polyalkenes. Recognition of the real mechanism of autooxidation in polymers is a key to developing strategies for the prevention of their degradation.

Abstract: The introduction of graphene into a polymer matrix can markedly improve its mechanical properties and electrical conductivity. We report herein a novel strategy to fabricate polyester/reduced graphene oxide composites via simultaneous dispersion and thermo-reduction of graphene oxide (GO) during in situ melt polycondensation. The pristine graphite was first oxidized using a strong oxidant acid to prepare GO, and then GO sheets were dispersed into ethylene glycol (EG), where a homogeneous dispersion of GO in EG was obtained with ultrasonication. Finally polyester/reduced graphene oxide composites were prepared via in situpolymerization of terephthalic acid (PTA) and ethylene glycol containing well dispersed GO. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and sedimentation experiments have been used to characterize the prepared composites. It is demonstrated that poly(ethylene terephthalate) (PET) chains may have been sucessfully grafted onto GO sheets during polymerization, accompanied by the thermo-reduction from GO to graphene. The TGA and XPS results showed that the content of grafted PET polymer was about to 60–80%, which indicates a homogeneous dispersion of GO sheets in the PET matrix, as demonstrated by SEM. Furthermore, a significant improvement in tensile strength and elongation at break of PET has been achieved. Therefore, our work provides a new way for the preparation of polyester/reduced graphene oxide composites and functionalization of graphene.

Abstract: The catalytic ring-opening polymerization of macrolactones to polyethylene-like polyesters was investigated using aluminum–salen complexes as the initiators. Contrary to the common understanding that high molecular weights in these reactions can only be achieved by enzymatic ring-opening polymerization due to the absence of ring tension in macrolactones, the aluminum–salen complexes produces poly(pentadecalactone)s with number-average molecular weights (Mn) of over 150 000 g/mol. Moreover, the same catalyst is also active in catalyzing the ROP of small and medium size lactones, which makes these aluminum–salen complexes highly potential catalysts for the cROP of lactones irrespective of ring size. These results show that it is possible to polymerize macrolactones to high molecular weight polyethylene-like polymers using cheap and robust metal-based catalysts. Even the so-called medium-sized lactones (ring size: 9–12) can be polymerized with a reasonably good activity to high molecular weight products, whi...

Abstract: α-Zirconium phosphate nanoplatelets have been alternatively combined with a cationic polyelectrolyte (polydiallyldimethylammonium chloride), a polyhedral oligomeric silsesquioxane or with alumina-coated silica nanoparticles, exploiting the layer-by-layer deposition. The obtained nanostructured assemblies have been applied to polyester, poly(ethyleneterephthalate), fabrics in order to enhance their thermal and fire stability, with particular attention to the reduction of smokes and toxic gases (carbon monoxide produced during the combustion). The treated fabrics evidenced a significant improvement of their thermal and thermo-oxidative stability, together with an increased time to ignition (86%), a lowering of heat release rate (26%), as well as a significant decrease in smoke release rate (25%) and production of carbon monoxide (35%). Thus, the proposed approach may turn out to be very advantageous for conferring flame retardancy to textiles.

Abstract: Four new polyesters based on 1,3-propanediol and different aliphatic dicarboxylic acids were used to prepare ropinirole HCl-loaded nanoparticles. The novelty of this study lies in the use of polyesters with similar melting points but different degrees of crystallinity, varying from 29.8% to 67.5%, as drug nanocarriers. Based on their toxicity to human umbilical vein endothelial cells, these aliphatic polyesters were found to have cytotoxicity similar to that of polylactic acid and so may be considered as prominent drug nanocarriers. Drug encapsulation in polyesters was performed via an emulsification/solvent evaporation method. The mean particle size of drug-loaded nanoparticles was 164-228 nm, and the drug loading content was 16%-23%. Wide angle X-ray diffraction patterns showed that ropinirole HCl existed in an amorphous state within the nanoparticle polymer matrices. Drug release diagrams revealed a burst effect for ropinirole HCl in the first 6 hours, probably due to release of drug located on the nanoparticle surface, followed by slower release. The degree of crystallinity of the host polymer matrix seemed to be an important parameter, because higher drug release rates were observed in poly- esters with a low degree of crystallinity.

Abstract: New bis(ω-hydroxyalkyl)imidazolium and 1,2-bis[N-(ω-hydroxyalkyl)imidazolium]ethane salts are synthesized and characterized; most of the salts are room temperature ionic liquids. These hydroxyl end-functionalized ionic liquids are polymerized with diacid chlorides, yielding polyesters containing imidazolium cations embedded in the main chain. By X-ray scattering, four polyesters are found to be semicrystalline at room temperature: mono-imidazolium-C11-sebacate-C6 (4e), mono-imidazolium-C11-sebacate-C11 (4c), bis(imidazolium)ethane-C6-sebacate-C6 (5a), and bis(imidazolium)ethane-C11-sebacate-C11 (5c), all with hexafluorophosphate counterions. The other imidazolium polyesters, including all those with bis(trifluoromethanesulfonyl)imide (TFSI−) counterions, are amorphous at room temperature. Room temperature ionic conductivities of the mono-imidazolium polyesters (4 × 10−6 to 3 × 10−5 S cm−1) are higher than those of the corresponding bis-imidazolium polyesters (4 × 10−9 to 8 × 10−6 S cm−1), even though the bis-imidazolium polyesters have higher ion concentrations. Counterions affect ionic conduction significantly; all polymers with TFSI− counterions have higher ionic conductivities than the hexafluorophosphate analogs. Interestingly, the hexafluorophosphate polyester, 1,2-bis(imidazolium)ethane-C11-sebacate-C11 (5c), displays almost 400-fold higher room temperature ionic conductivity (1.6 × 10−6 S cm−1) than the 1,2-bis(imidazolium)ethane-C6-sebacate-C6 analog (5a, 4.3 × 10−9 S cm−1), attributable to the differences in the semicrystalline structure in 5c as compared to 5a. These results indicate that semicrystalline polymers may result in high ionic conductivity in a soft (low glass tranition temperature, Tg) amorphous phase and good mechanical properties of the crystalline phase.

Abstract: Self-metathesis of undecenoic acid with [(PCy3)2Cl2Ru=CHPh] (2), followed by exhaustive hydrogenation yielded pure 1,20-eicosanedioic acid (5) (>99%) free of side-products from isomerization. Polycondensation with eicosane-1,20-diol (6), formed by reduction of the diol, yielded polyester 20,20 (Tm = 108 °C). By comparison, the known ADMET polymerization of undec-10-enyl undec-10-enoate (7), and subsequent exhaustive polymer-analogous hydrogenation yielded a polyester (poly-8) with irregular structure of the ester groups in the polymer chain (-O(C=O)- vs. -C(=O)O-) (Tm = 103 °C). Hydrogenation of secondary dispersions of poly-7 yielded aqueous dispersions of the long-chain aliphatic polyester poly-8.

Abstract: The applications of water-resistant and stain-resistant finishes to apparel have become widespread in recent years due to high consumer demand. In our previous research, we studied the formation of highly hydrophobic surfaces on cotton and polyester fabrics using a two-step treatment procedure, i.e., first forming silica sol by hydrolysis and subsequent condensation of tetraethoxysilane under alkaline conditions, applying the sol to the surfaces of cotton and polyester fabrics, and then applying hydrolyzed hexadecyltrimethoxysilane on the treated fabrics to impart hydrophobicity to the surfaces of the fabrics. In this research, we developed a novel one-step procedure to form highly hydrophobic surfaces on cotton and polyester fabrics using different modified silica sols. The first series of modified silica sol (“sol A”) was prepared by the reactions of a sol formed by alkaline hydrolysis of tetraethoxysilane and alkyltrialkoxysilanes in a NH4OH−ethanol solution. A second series (“sol B”) was prepared by t...

Abstract: Given the well-documented global corrosion challenge, [ 1 ] the development of universal coating systems for metals that provide both passive and active protection is desirable. The active part of such systems typically consists of either polymer precursors [ 2 , 3 ] or effi cient corrosion inhibitors contained inside small capsules disseminated throughout the coating. [ 4–9 ] In both cases, coating rupture and the onset of corrosion trigger a release of the active molecules, which can either physically repair the passive coating [ 2 , 3 ] or form a thin impermeable fi lm over the exposed metal surface. [ 4–9 ] Previous work in our group has focused on the use of corrosion inhibitors; the technology is well-established for aluminium surfaces and typically employs a hybrid sol-gel fi lm as the coating matrix. [ 8–10 ] However, despite some effort, no similarly effective system has been found for steel. [ 4 , 11 ] When applied to steel the same sol-gel fi lm tends to form a noticeably permeable coating that is highly susceptible to corrosive attack. [ 4 ] To improve the passive and active protection of steel, the coating matrix should be nonporous with excellent adhesion and incorporate well-dispersed capsules containing a suitable inhibitor in suffi cient quantity. Dense polymer-based coatings are a good option for the passive layer; those incorporating inhibitor directly [ 12 , 13 ] or inside capsules [ 5–7 ]

Abstract: A variety of substrates have been used for fabrication of microchips for DNA extraction, PCR amplification, and DNA fragment separation, including the more conventional glass and silicon as well as alternative polymer-based materials. Polyester represents one such polymer, and the laser-printing of toner onto polyester films has been shown to be effective for generating polyester-toner (PeT) microfluidic devices with channel depths on the order of tens of micrometers. Here, we describe a novel and simple process that allows for the production of multilayer, high aspect-ratio PeT microdevices with substantially larger channel depths. This innovative process utilizes a CO2 laser to create the microchannel in polyester sheets containing a uniform layer of printed toner, and multilayer devices can easily be constructed by sandwiching the channel layer between uncoated cover sheets of polyester containing precut access holes. The process allows the fabrication of deep channels, with ∼270 μm, and we demonstrate...

Abstract: Polyethylene terephthalate (PETE) consists of polymerized repeating units of ethylene terephthalate (C10H8O4) monomer. PETE is a recyclable plastic with identification code "1". World-wide PETE-1 is used as a synthetic fiber, polyester, packaging materials, containers of soft drinks and etc. The molecular weight of PETE-1 is 192gm/mole and out this 62.5% is Carbon (C), 33.3% Oxygen (O) and 4.2% Hydrogen (H). The main objective of this research is to convert the waste PETE-1 into liquid hydrocarbon fuel. The world-wide use of PETE-1 has gradually increased and most of the waste PETE-1 is being dumped into the environment instead of recycling; this creates environmental problem. In thermal degradation process, PETE-1 is being decomposed. It produces very hard solid complex substances of terephthalic acid and benzoic acid, which are not bio-degradable. NSR's experiment utilized Calcium Hydroxide (Ca(OH)2) as catalyst at 400- 530°C to obtain the liquid hydrocarbon fuel from PETE-1.

Abstract: Two sets of segmented polyurethane (PU) elastomers were prepared from 4,4!-methylenebis(phenyl isocyanate) (MDI), 1,4-butanediol (BD) and a polyester or a polyether polyol, respectively. The molecular mass of both polyols was 1000 g/mol. The stoichiometric ratio of isocyanate and hydroxyl groups was 1 and the polyol/total diol ratio changed from 0 to 1 in 0.1 steps. One step bulk polymerization was carried out in an internal mixer and the samples were compression molded for testing. The results proved that specific interactions determine the phase structure and properties of these mate- rials. Crystallinity was approximately the same in the two types of polyurethanes and the amount of relaxing soft segments was also similar. The determination of interaction parameters from solvent absorption and differences in glass transition temperatures indicated stronger interaction between hard and soft segments in the polyester than in the polyether polyurethane. Larger transparency of the polyester PU indicated the formation of smaller dispersed particles of the hard phase. The larger number of smaller hard phase units led to the formation of more physical cross-links distributed more evenly in the polymer. These differences in the phase structure of the polymers resulted in stronger strain hardening ten- dency, larger strength and smaller deformations for the polyester than for the polyether polyurethane.