Polycondensation Of Acid Research Articles

Improving lactic acid melt polycondensation: The role of co‐catalyst

AbstractA study on lactic acid polycondensation under melt conditions was carried out and a preliminary assessment revealed tin powder as a very good catalyst for poly(lactic acid) (PLA) synthesis by melt polycondensation while confirming previous information on SnCl2 good performance. However, these catalysts also promoted side reactions leading to racemization and yellowing of the final polymer. The use of p‐toluenesulphonic acid (p‐TSA) or triphenylphosphine (PPh3) as co‐catalysts proved to be very effective hindering colour formation and allowing synthesizing PLA samples with enhanced properties. The addition of these compounds to neat tin powder increased the PLA optical purity, whereas their addition to SnCl2 speeded up the polymerization. A significant increase in molecular weight, from 32,500 to 52,000 g mol−1, was recorded, with the new catalytic system SnCl2/PPh3 showing catalytic activity comparable with the one reported in the literature for SnCl2/p‐TSA. Several characterization techniques were used for assessing polymer samples: the molecular weights were determined by SEC, thermal behavior measured by DSC, and racemization extent calculated from specific rotation measurements. UV/vis spectroscopy was confirmed as a powerful technique for evaluating yellowing of final polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Polycondensation of Sebacic Acid with Primary and Secondary Hydroxyl Groups Containing Diols Catalyzed by Candida antarctica Lipase B

The aliphatic polyesters are normally synthesized by ester interchange reactions or direct esterification of hydroxyacids or diacid/diol combinations. Biotransformation, utilizing the enzymes as catalysts, was accepted as an alternative route for the synthesis of aliphatic polyesters and offers various advantages compared with the conventional, metal-catalyzed polymerization reactions. Previous studies indicated that lipase-catalyzed polycondensation reactions between diols and diacids occurred preferentially at primary hydroxyl groups of diols, when diols contained both primary and secondary hydroxyl groups. In this work, we investigated lipase-catalyzed polycondensation of diacids and secondary hydroxyl group–containing diols, and successfully synthesized polyesters by polycondensation with secondary hydroxyl groups as well as primary hydroxyl groups. Various diols, glycerol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, and 2,4-pentanediol were tested for the polycondensation. The polymerization was achieved by heating a mixture of lipase B, sebacic acid, and the diols in anhydrous toluene at 100 °C for 72 h. The resulting polymers were characterized by 1H and 13C NMR spectroscopy, Fourier transform–infrared spectroscopy, thermogravimetric analysis, and gel permeation chromatography.

Effect of 4,4′‐methylenediphenyl diisocyanate on thermal and mechanical properties of Bioflex/lactic acid polycondensate blends

ABSTRACTPolylactic acid as thermoplastic aliphatic polyester has attracted much attention because of its renewability and biodegradability. The current work investigates the influence of 4,4′‐methylenediphenyl diisocyanate (MDI) on thermal and mechanical properties of Bioflex/lactic acid polycondensate blends. Bioflex is a commercial product based on polylactic acid and a thermoplastic copolyester. Lactic acid polycondensate (polylactide) was obtained by direct melt polycondensation of lactic acid in the presence of stannous octoate as the catalyst. The increase in molecular weights (size exclusion chromatography) and the improved mechanical properties (stress–strain analysis) revealed that MDI under reactive extrusion conditions effectively adjusted the compatibility of Bioflex with 10 wt% of polylactide. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Star-shaped poly(lactic acid) with carboxylic acid terminal groups via poly-condensation

A series of star-shaped poly(lactic acid)s with carboxylic acid terminal groups have been synthesized by direct poly-condensation of lactic acid in the presence of a poly-carboxylic acid core molecule with triphenylphosphonium trifluoromethanesulfonate (TPP-T) catalyst.These star-polymers had thermal properties not very much different from those of star-shaped poly(lactic acid) with hydroxyl terminal groups and linear poly(lactic acid), irrespective of the structure of the core molecule and number of polymer arms. Solubility and degradability of these star-polymers were, however, greatly enhanced compared to those of star-polymers with hydroxyl terminal groups and increased depending on the number of polymer arms. From the star-shaped polymers, a variety of ammonium salts and the corresponding carboxyamides were successfully prepared.

Catalytic Effect of Magnesium Ions on Silicic Acid Polycondensation and Inhibition Strategies Based on Chelation

The catalytic role of Mg2+ ions in the polycondensation of silicic acid to form amorphous silica has been investigated in detail. This behavior is pH-dependent. As pH increases (herein, the three p...

Synthesis and characterization of PEGylated comb-like cationic polymer by polycondensation and ATRP

Abstract PEGylated poly(2-(dimethylamino)ethyl methacrylate) with comb-like architecture was synthesized by two-step polymerization. First, poly(oligo(ethylene glycol) malicate) (POEGMA) bearing pendant hydroxyl groups was prepared by direct polycondensation of oligo(ethylene glycol) and malic acid in the presence of scandium triflate as chemoselective catalyst. Then the poly(2-(dimethylamino)ethyl methacrylate) side chains were grafted from the POEGMA backbone by atom transfer radical polymerization (ATRP) after the hydroxyl groups were modified into bromo-ester form, resulting in a PEGylated cationic copolymer with branched architecture.

Dehydration Polycondensation of Dicarboxylic Acids and Diols Using Sublimating Strong Brønsted Acids

We investigated catalytic activities of strong brønsted acids for dehydration polycondensations of dicarboxylic acids and diols, which were carried out at low temperature (<100 °C) under reduced pressure (0.3-3 mmHg). Strong Brønsted acids, bis(perfluoroalkanesulfonyl)imide and perfluoroalkanesulfonic acid, showed higher activity than p-toluenesulfonic acid or rare-earth catalysts at 60 °C. In particular, bis(nonafluorobutanesulfonyl)imide (Nf(2)NH) showed the highest activity to synthesize not only aliphatic polyester (M(n) > 19000) but also aromatic polyester (M(n) > 7000). The used Nf(2)NH was sublimated from the reaction flask during polycondensation, and the sublimate, Nf(2)NH, was extra pure so that we can reuse the catalyst without loss of the activity in the dehydration polycondensations.

Preparation of Poly(l-lactic acid) Capsule Encapsulating Fertilizer

In this work, poly (l-lactic acid) (PLLA) microencapsulated urea as fertilizer was prepared in water in oil in water (W/O/W) system. PLLA used as capsule shell was prepared by polycondensation of l-lactic acid with p-toluene sulfonic acid as a catalyst at 140 °C. The prepared PLLA was used to encapsulate urea. Firstly, the aqueous urea solution was dispersed in oil solution of PLLA and chloroform containing polyvinyl alcohol (PVA) as a stabilizer with stirring at 800 rpm. Secondly, the water in oil emulsion was subsequently dispersed in PVA aqueous solution by stirring at 800 rpm to form W/O/W emulsion. Then, it was stirred for approximately 12 hours to evaporate chloroform in the system resulting in the formation of PLLA microencapsulated urea. It was finally centrifuged and dried in vacuum oven. The influence of water and oil phase ratio on the formation of capsule was studied. The obtained capsule was observed with an optical and scanning electron microscopes.

Bulk polycondensation of lactic acid by Maghnite-H+ a non-toxic catalyst

In this study, we report a novel approach to preparing poly (D, L-lactic acid) (PLA) as a biodegradable polymer. PLA was prepared by direct polycondensation of D, L-lactic acid using Maghnite-H+, a non-toxic proton exchanged Montmorillonite clay, as catalyst. We investigated in detail, the reaction conditions for the simple direct polycondensation of D,L-lactic acid, including the reaction times, temperatures, and catalyst amount. The molecular weight of synthesized PLA is dependent on both the reaction temperature, amount of catalyst and time. Kinetics indicated that the polycondensation of lactic acid behaves as second-order reaction mechanism. The method for PLA synthesis established here will facilitate production of PLA of various molecular weights, which may have a potential utility as biomaterials.

Synthesis and properties of bio‐based thermoplastic polyurethane based on poly (L‐lactic acid) copolymer polydiol

AbstractThe goal of this work is the synthesis of a new kind of bio‐based thermoplastic polyurethane (BTPU) based on poly(L‐lactic acid) (PLA) and poly(tetramethylene) glycol (PTMEG) segments via chain‐extension reaction of dihydroxyl terminated (HO‐PLA‐PTMEG‐PLA‐OH) copolymer using hexamethylene diisocyanate (HDI) as a chain extender. Polydiols were synthesized through polycondensation of lactic acid and PTMEG in bulk. The chemical structures and molecular weights of polydiols and BTPUs containing different segment lengths and weight fractions of PLA, were characterized by 1H‐NMR and FTIR. The effects of the structures on the physical properties of BTPUs were studied by means of DSC, SEM, and tensile test; crystallization behavior was characterized by POM. The DSC and SEM results indicate that PLA segment is perfectly compatible with PTMEG segment and the crystallization of BTPU is predominantly caused by PLA segment. Polydiol with lower PLA content shows lower Tg and lower crystallinity. Tensile test shows that the elongation at break of BTPU is above 340% at the composition of PLA/PTMEG = 80/20 (w/w). © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Water-Stable All-Biodegradable Microparticles in Nanofibers by Electrospinning of Aqueous Dispersions for Biotechnical Plant Protection

Pheromone eluting oligolactide (OLA) microcapsules immobilized in electrospun biodegradable polyester nanofibers were obtained by electrospinning of aqueous dispersions of the microcapsules. OLA was prepared by conventional melt polycondensation of lactic acid. Following the protocol of the solvent displacement method, OLA was dissolved in acetone and mixed with Brij S20 and the pheromone of the European grape vine moth, Lobesia Botrana, (E,Z)-7,9-dodecadien-l-yl acetate (DA). Up to 32 wt % of this mixture could be dispersed in water with colloidal stability of several weeks without any sedimentation. Without DA as well as OLA, no stable dispersions of OLA in water were obtained. Replacement of DA by classical hydrophobes typically used for miniemulsions did not yield stable dispersions, but the addition of octyl acetate, which shows structural similarity to DA, yielded stable dispersions in water up to 10 wt %. Dispersions of OLA/DA were successfully electrospun in combination with an aqueous dispersion of a biodegradable block copolyester resulting in water-stable nanofibers containing OLA/DA microcapsules. Release of DA from microcapsules and fibers was retarded in comparison with non-encapsulated DA, as shown by model studies.

Synthesis, nano-features, ex vivo anti-platelet aggregation and in vivo antithrombotic activities of poly-α,β-dl-aspartyl-l-arginine

In the nanoscale assembly-based design of antithrombotic agents, poly-α,β-DL-aspartyl-L-arginine (MW: 20741) was prepared from the thermal polycondensation of DL-aspartic acid and the amidation of polysuccimide with L-arginine. In the pH environments corresponding to the stomach (pH 1.2), intestinal tract (pH 7.6), blood and tissue fluids (pH 7.4) 4.8 × 104,2,−4,−6,−8 nM of poly-α,β-DL-aspartyl-L-arginine assembled to form diverse nano-species. The sizes of the smallest nanoparticle, nanobell and nanomango were less than 100 nm. At the oral doses of 0.72, 1.44 and 2.89 μmol kg−1, poly-α,β-DL-aspartyl-L-arginine dose-dependently inhibited the ex vivo platelet aggregation and the in vivo thrombosis of the treated rats. By assembling to form diverse nano-species, the absorption of oral poly-α,β-DL-aspartyl-L-arginine in the stomach and intestinal tract could be assisted.

Direct synthesis and melt‐drawing property of aramids by bulk polycondensation of isophthalic acid with m‐phenylenediamine and 3,4′‐oxydianiline

AbstractThe direct polycondensation of isophthalic acid with a mixture of 1,3‐phenylenediamine (m‐PDA) and 3,4′‐diaminodiphenyl ether (3,4′‐ODA) could be successfully performed in the bulk to afford the expected co‐aramids for the first time. The co‐aramids with low molecular weights and 3,4′‐ODA contents higher than 50 mol% display excellent thermoplasticity and melt‐drawing property. Indeed, several meters long filaments with 12 μm diameter could be produced. In addition, the environmentally friendly method for the preparation of aramid materials as well as the demonstration of their filament formation will open up the new possibility to prepare aramid fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Biocompatible and Biodegradable Triblock Copolymers via ATRP

Novel well-defined ABA-type triblock copolymers, (PMAIPGal-b-PLA-b-PMAIPGal), were synthesized by a three-step procedure: (a) melt polycondensation of L-lactic acid using stannous chloride (SnCl2•2H2O) as a catalyst, resulting in a hydroxyl-terminated prepolymer by alkyd condensation with 1,4-butanediol, followed by (b) esterification of the PLA hydroxyl end-groups with 2-bromoisobutyryl bromide, and (c) ATRP of 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (MAIPGal) by the bromoisobutyryl initiating groups. The resultant copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The biocompatible and biodegradable copolymers have potential applications as tissue engineering biomaterials or controlled release drug delivery systems.

Microwave-assisted low-temperature dehydration polycondensation of dicarboxylic acids and diols

Microwave-assisted low-temperature dehydration polycondensation of dicarboxylic acids and diols

Influence of Polyamines and Related Macromolecules on Silicic Acid Polycondensation: Relevance to “Soluble Silicon Pools”?

The influence of a number of N-containing macromolecules on the polycondensation of silicic acid to form amorphous silica is studied by the combined use of 29Si NMR spectroscopy and the silicomolybdate test. Polymeric additives include poly(allylamine hydrochloride) (PAH), the poly(aminoamide) dendrimer of generation 1 (PAMAM-1), poly(ethyleneimine) (PEI), and poly(vinylpyrrolidone) (PVP). These studies were performed under biologically relevant conditions (pH 5.4 and 7.0) using aqueous solutions of isotope-labeled sodium [29Si]metasilicate as the precursor compound. It was found at pH 5.4 that all additives accelerate silicic acid polycondensation, except for PVP, which exerts a minor silicic acid stabilizing effect. At pH 7.0, polycondensation is much faster in the presence of PAMAM-1, PEI, and PAH. However, PVP significantly stabilizes mono- and disilicic acid. Silica precipitates were also studied by 29Si NMR spectroscopy. The effect observed for PVP is striking and indicates that the silicic acid pol...

Synthesis and Hydrolytic Degradation of Substituted Poly(DL-Lactic Acid)s.

Non-substituted racemic poly(DL-lactic acid) (PLA) and substituted racemic poly(DL-lactic acid)s or poly(DL-2-hydroxyalkanoic acid)s with different side-chain lengths, i.e., poly(DL-2-hydroxybutanoic acid) (PBA), poly(DL-2-hydroxyhexanoic acid) (PHA), and poly(DL-2-hydroxydecanoic acid) (PDA) were synthesized by acid-catalyzed polycondensation of DL-lactic acid (LA), DL-2-hydroxybutanoic acid (BA), DL-2-hydroxyhexanoic acid (HA), and DL-2-hydroxydecanoic acid (DA), respectively. The hydrolytic degradation behavior was investigated in phosphate-buffered solution at 80 and 37 °C by gravimetry and gel permeation chromatography. It was found that the reactivity of monomers during polycondensation as monitored by the degree of polymerization (DP) decreased in the following order: LA > DA > BA > HA. The hydrolytic degradation rate traced by DP and weight loss at 80 °C decreased in the following order: PLA > PDA > PHA > PBA and that monitored by DP at 37 °C decreased in the following order: PLA > PDA > PBA > PHA. LA and PLA had the highest reactivity during polymerization and hydrolytic degradation rate, respectively, and were followed by DA and PDA. BA, HA, PBA, and PHA had the lowest reactivity during polymerization and hydrolytic degradation rate. The findings of the present study strongly suggest that inter-chain interactions play a major role in the reactivity of non-substituted and substituted LA monomers and degradation rate of the non-substituted and substituted PLA, along with steric hindrance of the side chains as can be expected.

Thermal degradation behaviors of phosphorus–silicon synergistic flame‐retardant copolyester

AbstractA novel phosphorus‐containing poly (ethylene terephthalate) (PET) copolyester/nano‐SiO2 composite (PET‐co‐DDP/SiO2) was synthesized by in situ polycondensation of terephthalic acid (TPA), ethylene glycol (EG), [(6‐oxide‐6H‐dibenz[c,e] [1,2]oxaphosphorin‐6‐yl)‐methyl]‐butanedioic acid (DDP), and nano‐SiO2. The morphology of PET nanocomposites was observed by using transmission electron microscope and scanning electron microscope. It was found that the SiO2 nanoparticles were dispersed uniformly at nanoscale in the copolyesters with content 2 wt %. The thermal degradation behavior of PET nanocomposites was investigated by thermogravimetric analysis performed with air and nitrogen ambience. The activation energies of thermal degradation were determined using Kissinger and Flynn–Wall–Ozawa methods, respectively. The results obtained from Kissinger method showed that the activation energy was increased with the introduction of SiO2. Moreover, the activation energy is decreased for PET‐co‐DDP system in nitrogen and air. The results also indicated that the SiO2 and DDP had synergic effect on the early decomposition and the late charring in air. Furthermore, in the PET‐co‐DDP/SiO2 system, the activation energy increased when the DDP component increased. However, the opposite results were obtained when the Flynn–Wall–Ozawa method was used. That was because the Doyle approximation stands correct as the conversion degree is from 5% to 20%. The effects of SiO2 and DDP on the PET thermal degradation were lower in nitrogen than in air. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Kinetic Optimization of Folic Acid Polymer Conjugates for Drug Targeting

Problem statement: Folic Acid (FA) is an essential, bioavailable water soluble B-complex vitamin that helps in the replication of normal cells. It is obtained from natural sources and it deficiency can leads to oncogenic cells development. Within this frame work in mind, we designed and synthesized a new bioconjugate carrier that can enhance the effectiveness of FA. Approach: The polymeric carrier: Polysucscinimide (PSI) was synthesized via the polycondensation of aspartic acid by attaching 3-(N,N-Dimethylamino) Propylamine (DMP) and 1,3-Ppropylenediamine (PDA) for solubility behavior and reactivity for FA site anchoring. Also the use of an ester 2-(1H-benzotrial-1-yl)-1,1,3,3-tetramethylurium Hexafluorophosphate (HBTU) as coupling agent to FA. The bioreversible binding of the water-soluble and biocompatible macromolecular were attested through kinetic studies. The kinetic reactions were investigated through the nuclear resonance (H1NMR) spectra analysis. Results and Conclusion: The H1NMR optimization reaction times were found within the range of 120-130 min (80-85%) as optimum coupling. The yield of the FA occurred within the same time range but with maximum incorporation between 90-100%. The growth of FA incorporation in terms of reaction time resulted to an increase inherent viscosity relative to the decrease of water solubility of the conjugate obtained.

Crystal and Thermal Properties of PLLA/PDLA Blends Synthesized by Direct Melt Polycondensation

We herein report the effects of the component ratio and method of blending on the synthesis of stereocomplex poly(lactic acid) (SC-PLA) based on poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) prepolymers. PLLA and PDLA were prepared by direct melt polycondensation of lactic acid (DMP). Combined with the dual catalyst system, PLA prepolymers with Mw more than 20,000 were prepared by DMP. PLLA was mixed by powder blending or melt blended with PDLA. It is revealed that melt-point and spherulite growth rate of SC-PLA is strongly dependent on the perfection of SC structure. The melt point of PLA can be increased by nearly 50 °C because of the particular strong intermolecular interaction between PLLA and PDLA chains. Solid-state polycondensation (SSP) is an efficient method to increase the molecular weight of SC-PLA, but it can have a negative effect on the regularity of linear chains of SC-PLA. Thermogravimetry analyzer (TGA) results show that SC structure cannot cause the delay reaction on the thermal degradation of PLA.