Direct Copolycondensation Research Articles

Effect of Chemical Composition Variant and Oxygen Plasma Treatments on the Wettability of PLGA Thin Films, Synthesized by Direct Copolycondensation.

The synthesis of high molecular weight poly (lactic-co-glycolic) acid (PLGA) copolymers via direct condensation copolymerization is itself a challenging task. Moreover, some of the characteristic properties of polylactide (PLA)-based biomaterials, such as brittleness, hydrophobicity, and longer degradation time, are not suitable for certain biomedical applications. However, such properties can be altered by the copolymerization of PLA with other biodegradable monomers, such as glycolic acid. A series of high molecular weight PLGAs were synthesized through the direct condensation copolymerization of lactic and glycolic acids, starting from 0 to 50 mol% of glycolic acid, and the wettability of its films was monitored as a function of the feed molar ratio. Copolymerization was performed in the presence of a bi-catalytic system using stannous chloride dihydrate and methanesulfonic acid (MSA). The viscosity average molecular weight of the resulting PLGA was in the range of 80k to 135k g/mol. The PLGA films were prepared using the solvent casting technique, and were treated with oxygen plasma for 2 min. The water contact angle of the PLGA films was determined before and after the oxygen plasma treatments, and it was observed that the wettability increased with an increase in the glycolic acid contents, however, the manifolds increased after 2 min of oxygen plasma treatments.

One-pot method for the synthesis of sulfonated poly(1,3,4-oxadiazoles) based on 4,4’-oxydibenzoic acid

A series of new copolymers of poly(1,3,4-oxadiazole) that contain side protogenic sulfo groups are synthesized by the direct copolycondensation of terephthalic and 4,4’-oxydibenzoic acids and hydrazine sulfate in oleum. Variation in the polycondensation conditions makes it possible to synthesize copolymers containing phenylene moieties with either 4-sulfo-10,10-dioxophenoxatiine or 4,4’-oxybis(3-sulfophenyl) moieties or a combination of the three moieties. This approach permits easy control over the physicochemical properties of the copolymers and the amount of protogenic sulfo groups. It is shown that the introduction of sulfonated moieties into copolymer molecules makes it possible to obtain materials with high values of ionexchange capacity (1.5 mmol/g) and water absorption (110%), while the strength and thermal stability inherent in poly(p-phenylene 1,3,4-oxadiazoles) remain intact.

Direct copolycondensation of biobased elastomers based on lactic acid with tunable and versatile properties

Tunable and versatile biobased copolyesters with excellent performances in nanocomposites, polylactide tougheners and shape memory were synthesized and characterized.

Structural Characterization of Serial Novel Star-Shaped Biodegradable Material Poly(lactic acid-<i>co</i>-melamine)

Using flame retardant melamine (MA) as a new aromatic core, biodegradable material poly (lactic acid-co-melamine) [P(LA-co-MA)] with different molar feed ratios are synthesized via direct melt copolycondensation. The structures of P(LA-co-MA) s are characterized by FT-IR,1H-NMR,13C-NMR and GPC. The results indicate that MA moiety as the core is incorporated into the PLA backbone as expected, and the obtained products are copolymers indeed.

Thermally crosslinked sulfonated polyethersulfone proton exchange membranes for direct methanol fuel cells

Abstract Sulfonated polyethersulfones (sPES) with thermally crosslinkable allyl or propargyl endgroups were synthesized and evaluated as methanol-tolerant proton exchange membranes (PEMs) for use in a direct methanol fuel cell (DMFC). sPES with a controlled degree of sulfonation (DS) were generated by direct copolycondensation of sulfonated and nonsulfonated dichloro-monomers with bisphenol-A, and synthesis of crosslinkable sPES was completed by subsequent end group modification with allyl or propargyl halide. Dissolved polymers were simply cast to tough membranes that underwent thermal crosslinking at an elevated temperature. The final PEMs were obtained after further cation exchange of the membranes to generate the protonated form. The PEM films were rigorously characterized to elucidate their electrochemical and mechanical properties. It was found that the allyl-terminated sPES generally showed higher proton conductivity and methanol permeability than the propargyl-terminated counterparts with a similar DS, plausibly due to lower crosslinking reactivity of the allyl group relative to the propargyl groups. The allyl-terminated sPES was successfully fabricated into a membrane electrode assembly (MEA) by using sPES/Nafion mixed ionomers as the binder, and a power performance of 23.5 mW/cm2 was achieved in a DMFC single cell test in air-breathing semi-passive mode after activation for six days.

New Luminescent Mesoporous Material Covalent Bonded with Europium (III) Organic/Inorganic/Polymeric Hybrid

Luminescent ternary organic-inorganic-polymeric mesoporous hybrid material Eu-(PA-SBA-15)-PMAA was prepared in situ through hydrothermal and solvothermal method based on hydrolysis and co-polycondensation. The organic ligand PA (O-phthalic anhydride) was modified by silane coupling reagent APS ((3-aminopropyl) triethoxysilane) to generate the precursor PA-Si which was used to form the ordered inorganic Si-O networks through direct co-hydrolysis and co-polycondensation process with SBA-15 in the presence of Pluronic P123 surfactant as a template. TEOS (tetraethoxysilane) was used to promote the hydrolysis and condensation process. Eu3+ complex Eu(PA-Si)3 was covalently linked to the ordered mesoporous SBA-15 and organic polymer PMMA which was synthesized by addition polymerization reaction of the monomer MMA (methyl methacrylate) in the presence of the initiator BPO (benzoyl peroxide). Moreover, the binary organic-inorganic mesoporous hybrid material Eu (PA-SBA-15)3 without polymer was also synthesized simultaneously for comparison. The luminescence properties of the hybrids were characterized in detail. The results show the ternary hybrid exhibits stronger emission intensity, longer lifetime and higher quantum efficiency than binary one which proves that the introduction of the organic polymer PMMA brings improvement to the hybrid system.

Synthesis and characterization of a novel functional biodegradable material, poly(lactic acid-co-borneol)

Directly starting from D,L-lactic acid (LA) and L-borneol, novel biodegradable material poly(lactic acid-co-borneol) (PLAB) was synthesized via melt polycondensation. When the molar feed ratio LA/borneol is 64/1, the influences of different conditions including catalyst kinds and its dosage, copolymerization time, and temperature on the synthesis of the polymer are discussed. When the SnO was used as catalyst and the dosage was 0.3 wt% of the prepolymer, the 5 h direct melt polycondensation at 170 °C and absolute pressure of 70 Pa after prepolymerization gave the copolymer with the maximum intrinsic viscosity [η], 1.51 dL g−1. The structure of copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR). According to the appropriate synthetic conditions, the copolymers with different molar feed ratios were synthesized and systematically characterized by [η], gel permeation chromatography (GPC), differential scanning calorimetry, thermogravimetric, and X-ray diffraction (XRD). The GPC results show that the maximum weight average molecular weight (M w) of PLAB is 11,900, when the molar feed ratio LA/borneol is 64/1. With the increase of the molar feed ratio of borneol, [η], M w and its polydispersity index (M w/M n) increase gradually. Due to the introduction of borneol into the copolymer, the glass-transition temperature (T g) decreases gradually with the increasing feed ratio of borneol. The direct melt copolycondensation is a cheap and practical method for the synthesis of borneol modified polylactic acid, a potential solid borneol flavor, polymeric drug, and functional drug carrier.

Synthesis of biodegradable material poly(lactic acid‐co‐aspartic acid) via direct melt polycondensation and its characterization

AbstractDirectly starting from L‐lactic acid (LA) and L‐aspartic acid (Asp), biodegradable material poly(lactic acid‐co‐aspartic acid) [P(LA‐co‐Asp)] was synthesized via melt polycondensation. The synthetic conditions, including type and dosage of catalyst, temperature, and time of copolymerization, and influence of molar feed ratio were discussed. The structure and properties of the copolymer were systematically characterized with FTIR, 1H‐NMR, GPC, DSC, and XRD. With the increase of Asp in the feed, [η] and Mw decreased, and the crystallinity of the copolymer disappeared gradually. Compared to the homopolymer, poly(L‐lactic acid) synthesized via melt polycondensation and the copolymer P(LA‐co‐Asp) had a higher glass‐transition temperature (Tg). The copolymer P(LA‐co‐Asp) with Mw of 4400–24300 Da was obtained, which could meet the demand as a drug‐delivery carrier material. Compared to the ring‐opening polymerization of the cyclic intermediates, including lactide, the novel direct copolycondensation method was a cheap and practical method for the synthesis of copolymer P(LA‐co‐Asp) as biomedical materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis of poly(D,L‐lactic acid) modified by cholic acid via direct melt copolycondensation and its characterization

AbstractFrom D,L‐lactic acid and the natural functional molecule cholic acid (CA), the biodegradable material poly(D,L‐lactide–cholate) was synthesized via direct copolycondensation. For the CA/lactic acid (LA) molar feed ratio of 1/64, the optimal synthesis conditions were as follows: a prepolymerization time of 8 h, 0.3 wt % SnO catalyst, and melt copolycondensation for 8 h at 160°C, which gave a novel star‐shaped poly(D,L‐lactic acid) (PDLLA) modified by CA with the maximum weight‐average molecular weight of 5600 Da at a yield of 51.9%. The copolymer poly(D,L‐lactide–cholate) at different molar feed ratios was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetry, and X‐ray diffraction. Decreasing the molar feed ratio of CA/LA from 1/15 to 1/128 reduced the average number of CA units embedded in the copolymer from 4 to 1. With 1/15 CA/LA, the copolymer was not a star‐shaped polymer, and its weight‐average molecular weight was the biggest (weight‐average molecular weight = 12,700 Da, weight‐average molecular weight/number‐average molecular weight = 1.68). With 1/32 CA/LA, the copolymer with two CA units was not a star‐shaped polymer either. With 1/64, 1/100, and 1/128 CA/LA, the copolymer mainly had one CA unit core embedded as a normal star‐shaped PDLLA with four arms, and certain crystallinity could be detected. The novel direct copolycondensation method was simple and practical for the synthesis of the asymmetrical star‐shaped PDLLA material, and it was advantageous for this PDLLA material embedded in the special bioactive molecule CA to be applied in the field of drug delivery and tissue engineering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis of poly(lactic acid)-poly(phenyl phosphate) via direct polycondensation and its characterization

Starting from d,l-lactic acid (d,l-LA), ethylene glycol (EG) and phenyl dichlorophosphate (PDP), poly(lactic acid)-poly(phenyl phosphate) was synthesized via direct copolycondensation. The novel poly(lactic acid) (PLA) copolymer containing phosphorus was characterized with FTIR, 1H NMR, 31P NMR, GPC, and DSC. The GPC results showed that, after the prepolymerization of d,l-LA and EG, the direct melt copolymerization of oligomer and PDP gave copolymer with higher weight-average molecular (Mw) than the direct solution copolymerization. The optimal synthetic conditions of the direct melt copolymerization, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, were all discussed in detail. When catalyzed by 0.5% (weight percent) ZnO under 160°C and 70 Pa, 8 h’s copolymerization gave the copolymer with maximum Mw 9,200 Da. When the feed molar ratio of d,l-LA/EG/PDP was 20/1/1 instead of 20/1/2, the melt polymerization under the above conditions gave the copolymer with maximum Mw 27,700 Da (Mw/Mn 1.07). The novel one-step method could be an alternative route to the synthesis of poly(lactic acid)-poly(phosphate ester) instead of the traditional two-step method using lactide as intermediate. At the same time, the novel PLA copolymer containing phosphorus with phenyl group may give this material more chance for the further structure modification as expected.

Synthesis and characterization of functional aliphatic copolyesters

AbstractFunctional aliphatic copolyesters of succinic acid (SA) and citric acid (CA) were synthesized via direct copolycondensation in the presence of 1,4‐butanediol, with titanium(IV) butoxide as a catalyst. The effects of the comonomer and comonomer ratio on the polycondensation and the melting and glass‐transition temperatures were investigated. The melting temperature was very sensitive to the molar ratio of the SA–CA comonomer units. The chain extension of this poly(butylene succinate citrate) was carried out with hexamethylene diisocyanate. The intrinsic viscosity, crystallinity percentage, and rheological properties of these copolyesters were also studied. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3232–3239, 2002

Novel Copolyamides Containing [60]Fullerene in the Main Chain

Abstract Novel copolymers, poly(1,4-oxybisphenylene fullerenobisacetamide-co-1,4-oxybisphenylene isophthalamide)s, which contained [60]fullerene in the main chain, were synthesized by the direct copolycondensation of a mixture of [60]fullerenobisacetic acid and isophthalic acid with 4,4′-diaminodiphenyl ether in the presence of triphenylphosphite and pyridine. Light scattering measurements for the copolymers showed a weight-average molecular weight Mw of about 5-6 × 104. The UV-visible spectra of the copolymers exhibited the characteristics of the parent fullerene derivative. The absorption edge red-shifted from 370 nm for poly(1,4-oxybisphenylene isophthalamide) to about 700 nm for the copolymers.

The modification of lactic acid based poly(ester-urethane) by copolymerization

Copolymers of L-lactic acid (LLA) with DL-mandelic acid (DLMA), 4-hydroxybenzoic acid, 4-acetoxybenzoic acid, DL-malic acid, or anhydrous citric acid were synthesized via direct copolycondensation in the presence of 1,4-butanediol, using stannous octoate as catalyst. The effect of the comonomer and the comonomer ratio on polycondensation and the glass transition temperature were investigated. The glass transition temperature of amorphous poly(L-lactic acid-co-DL-mandelic acid) increased linearly from 33° to 56°C as the mandelic acid composition was increased from 0 to 45 mol %. For urethane synthesis, prepolymers of LLA and DLMA were condensation polymerized with compositions of 100/0, 90/10, and 80/20 (mol % in feed). The preparation of poly(ester-urethane) (PEU) was carried out in a stirred glass reactor, using 1,6-hexamethylene diisocyanate and isophorone diisocyanate in melt. The glass transition temperature of poly(L-lactic acid-co-DL-mandelic acid-urethanes) showed a marked increase with increased mandelic acid composition. The molecular weights of these urethanes were lower than for PEU based on poly(L-lactic acid). Such a depression in the degree of polymerization is attributed to the steric hindrance of the bulky phenyl group as a side chain of mandelic acid. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1865–1872, 1997

Surface functionalized colloidal silica particles from an inverse microemulsion sol gel process

Colloidal silica particles are prepared via a sol gel technique carried out in an inverse microemulsion of water in a toluene solution of tetraethoxysilane (TEOS), stabilized by either an anionic surfactant AOT or isopropanol. Functionalized material was obtained using a functional coupling agent (RO)3Si(CH2)3X, X being a functional group such as methacryloyl, thiol, vinyl, amino group, or a chlorine atom. Functionalization can be carried out either directly via the direct copolycondensation of TEOS and the coupling agent, or in a two-step process involving a core-shell polycondensation of the coupling agent onto preformed silica particles. Kinetic studies of the copolycondensation are carried out using either29Si NMR analysis or liquid chromatography. They show that the consumption of TEOS is more rapid than that of the coupling agent. The materials are characterized both chemically (elemental analysis, FTIR,13C and29Si NMR CPMAS analysis), and by their particle size. The silica functionalized with a polymerizable methacryloyl group is encapsulated by a polymer layer in an inverse emulsion polymerization of acrylic acid. After inversion of the emulsion in water, the resulting material is covered with a layer of hydrophobic polymer in a conventional emulsion polymerization.

Polycaprolactone–poly(ethylene glycol) block copolymer, I: synthesis and degradability in vitro

AbstractA new type of biodegradable polymer material, poly(caprolactone)–poly(ethylene glycol) block copolymer (PCL‐b‐PEG), was synthesized by means of direct copolycondensation of ε‐caprolactone with poly(ethylene glycol) in the presence of a Ti(OBu)4 catalyst. The degradability of the polycaprolactone was improved by introducing a PEG component into it. The degradation of PCL‐b‐PEG copolymer increase with a decreasing crystallinity of the copolymer, and can be controlled by adjusting the component ratio of the copolymer.

A new biodegradable copolymer of glycolic acid and lactones with relatively low molecular weight prepared by direct copolycondensation in the absence of catalysts

Relatively low-molecular-weight copolyesters of glycolic acid (GA) with lactones such as gamma-butyrolactone (BL), delta-valerolactone (VL), and epsilon-caprolactone (CL) were synthesized by copolycondensation without catalysts. The resulting copolyesters are intended as carriers for drug delivery systems. Copolyesters with approximately 85 mol% GA (number-average molecular weight (Mn): 2900 +/- 100) are crystalline and solid and show a parabolic-type in vivo degradation pattern. The in vivo degradation of amorphous-pasty poly (GA/CL) (approximately 50/50 mol%) changed from parabolic-type to linear-type to S-type pattern as their molecular weight increased. A luteinizing hormone-releasing hormone agonist, [D-Leu6, des-Gly10]-LHRH ethylamide monoacetate (LHRH agonist), was incorporated into small cylinders with these copolyesters. An initial burst of LHRH agonist was observed for cylinders prepared with parabolic-type degrading copolyesters, in contrast to a marked delay in LHRH agonist release for cylinders prepared with S-type degrading copolyesters. The resulting daily dose of drug was maintained an approximately constant, though decreasing stepwise with time. For example, the daily amount of LHRH agonist released in vivo from a cylinder prepared with poly(GA/CL) (50/50 mol%; Mn = 4500) was 61 +/- 39 micrograms/day throughout an experimental period of 10 weeks with a corresponding pharmacological effect on the rat prostate.

A new biodegradable implant consisting of waxy-type poly(ε-caprolactone-co-δ-valerolactone) and estramustine

Abstract Biodegradable waxy-type copolyesters were prepared by direct copolycondensation of e-caprolactone (CL) and δ-valerolactone (VL) in the absence of catalysts, to apply as implantable matrices for drug delivery systems. The copolyesters are much more subject to erosion than their homopolyesters, in which the degradation is further accelerated by the action of lipase-type enzyme. Estramustine was incorporated into a small cylinder of waxy-type poly(CL-co-VL) with 92 mol% CL unit device by the so-called melt-pressing technique. The in vivo capability of this device was evaluated by implanting into the back of male rats. The drug release, although accompanying a burst phenomenon in the initial stage, was kept constant throughout an experimental period of 19 weeks from the 1st to 20th week. In this case, the release pattern was parallel to the degradation pattern, in support of the release being the rate-limiting step in the degradation of the polymer. The results showed about 75% of the initial drug content was still present in the device even after 20 weeks implantation. This finding means that the biodegradable poly(CL-co-VL) wax is very useful as an implantable matrix for a drug delivery system which controls the release over a relatively long period of time.

Evaluation of New Pasty-Type Implantable Devices Consisting of Poly(.EPSILON.-caprolactone/.DELTA.-valerolactone) and Estracyt or Estramustine.

Biodegradable pasty-type copolyesters with a relatively low molecular weight of 4500 were synthesized by direct copolycondensation of epsilon-caprolactone (CL) and delta-valerolactone (VL) in the absence of catalysts to evaluate in vivo capabilities of the polymer for implantable controlled release devices in drug delivery systems. The devices in cylindrical shape were prepared by the melt-pressing technique using pasty-type copoly(CL/VL) with 53 mol% CL unit, in which Estracyt and estramustine were used as a water soluble and insoluble drug, respectively. The degradation and drug release in vivo of the devices were examined by subcutaneous implantation in the backs of male rats. The degradation of the device was remarkably accelerated by the presence of hydrophilic Estracyt, and was slightly suppressed by hydrohobic estramustine. The estramustine release profile roughly corresponded to the polymer degradation one. It was found that the degradation of the polymer in the device was affected by hydrophilicity of the drug. A reasonable release of estramustine from the device was kept for a period of more than 20 weeks. Furthermore, the release of the drugs in vivo was able to lead to an atrophy of accessory sex organs such as ventral prostates (VP) and right-side seminal vesicle (SV), resulting in pharmacological influence.

Synthesis of low-molecular-weight copoly( l-lactic acid/ɛ-caprolactone) by direct copolycondensation in the absence of catalysts, and enzymatic degradation of the polymers

Low-molecular weight copolymers ofl-lactic acid (LA) and ɛ-caprolactone (CL) were synthesized by direct copolycondensation without catalysts at 200°C under a nitrogen atmosphere. The reaction proceeds by direct condensation between linear LA and linear 6-hydroxycaproic acid produced by hydrolysis of the cyclic CL. These copolymers were characterized with respect to molecular weight by gel permeation chromatography, composition by1H nuclear magnetic resonance (n.m.r.) spectroscopy, sequence by13C n.m.r. spectroscopy, and crystallinities by both differential scanning calorimetry and X-ray measurement. The morphology of copoly (LA/CL) can be subdivided into three states as a function of monomer composition according to the differences inTg and crystallinity, e.g. solid (0–15 mol% CL composition ranges), paste (30–70 mol% CL composition ranges) and wax (85–100 mol% CL composition ranges). Thein vitro degradation of the copolymer was examined by treatment in buffer solutions with and without enzymes and, as a result,Rhizopus delemer lipase showed the strongest degradation activity. In this case, the degree of enzymatic degradation is strongly dependent on the morphology of copoly(LA/CL), in which the pasty copolymer is much more subject to hydrolysis than the solid and waxy copolymers. For comparison thein vivo degradation of the copolymer was investigated by implanting it subcutaneously in the back of rats.

In vivo characteristics of low molecular weight copolymers composed of L-lactic acid and various dl-hydroxy acids as biodegradable carriers for drug delivery systems

Low molecular weight and amorphous copolyesters composed of 70 mol% l-lactic acid and 30 mol% dl-hydroxy acids such as dl-lactic acid, dl-α- hydroxy-n- butyric acid, dl-α-hydroxyisovaleric acid and dl-α-hydroxyisocaproic acid were synthesized by direct copolycondensation in the absence of catalysts, to evaluate their in vivo capabilities as biodegradable carriers for drug delivery systems. For this purpose, the copolyester was moulded into a small cylindrical specimen under melt-pressing technique and implanted subcutaneously in the back of male adult rats. The in vivo degradation pattern can be subdivided into three types: the formations of parabolic type ( l-LA/ dl-HBA copolymer), linear type ( l-LA/ dl-LA copolymer) and S type ( l-LA/ dl-HIVA and l-LA/ dl-HICA copolymers). A luteinizing hormone-releasing hormone agonist, des-Gly 10-( d-Leu 6)-LH-RH ethylamide monoacetate (LH-RH agonist), was incorporated into the small cylinders of copolyester formulations, of which the strongest pharmacological influence was observed in a copoly( l-LA/ dl-HICA) formulation system, resulting in the maintenance of effective pharmacological influence throughout an experimental period of 15 wk, at which the in vivo release rate of LH-RH agonist was held constant at approximately 45/μg/d.