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

Using D ,L ‐lactic acid (LA) and multifunctional group compound triethanolamine (TEA) as starting materials, a novel biodegradable material poly(D ,L ‐lactic acid‐triethanolamine) [P(LA‐TEA)] was directly synthesized by simpler and practical melt polycondensation. The appropriate synthetic condition was discussed in detail. When the molar feed ratio LA/TEA was 30/1, the optimal synthesis conditions were as follows: a prepolymerization time of 12 h; 0.5 weight percent (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 TEA with the maximum intrinsic viscosity [η] 0.93 dL g⁻¹. The copolymer P(LA‐TEA) as a different molar feed ratio was characterized by [η], Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H‐NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). Increasing the molar feed ratio of LA/TEA, T_g and M_w increased. However, all copolymers were amorphous, and their T_g (12.2°C–32.5°C) were lower than that of homopolymer PDLLA. The biggest M_w was 9400 Da, which made the biodegradable polymer be potentially used as drug delivery carrier, tissue engineering material, and green finishing agent in textile industry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biodegradations of statistical copolymers composed of D,L‐lactide and cyclic carbonates

Syntheses and biodegradation of statistical copolymers of D ,L ‐lactide (D ,L ‐LA) with trimethylene carbonate (TMC), rac‐1‐methyltrimethylene carbonate (1‐MTMC) and 2,2‐dimethyltrimethylene carbonate (2,2‐DTMC) were investigated at various monomer ratios using SmMe(C₅Me₅)₂THF as an initiator at 80 °C for 24 h in toluene. Biodegradations of poly(D ,L ‐LA‐co‐racemo‐1‐MTMC) (95/5) and poly(D ,L ‐LA‐co‐2,2‐DTMC) (98/2) with a compost at 60 °C proceed rapidly. Enzymatic degradations of these polymers were also performed using cholesterol esterase, lipoprotein lipase and proteinase K. Only poly(D ,L ‐LA‐co‐TMC) was biodegraded with cholesterol esterase, while poly(TMC), poly(1‐MTMC), poly(2,2‐DTMC) and poly(D ,L ‐LA) were barely degraded with these enzymes. Biodegradations of poly(D ,L ‐LA‐co‐TMC) (87/13) and poly(D ,L ‐LA‐co‐racemo‐1‐MTMC) (95/5) are rapid using proteinase K. Physical properties of these copolymers were also described. © 2003 Society of Chemical Industry     

A biodegradable diblcok copolymer poly(ethylene glycol)‐block‐poly(L‐lactide‐co‐2‐methyl‐2‐carboxyl‐propylene carbonate): Docetaxel and RGD conjugation

A diblcok copolymer monomethoxy poly (ethyleneglycol)‐block‐poly(L ‐lactide‐co‐2‐methyl‐2‐carboxyl‐propylene carbonate) (MPEG‐b‐P(LA‐co‐MCC)) was obtained by copolymerization of L ‐lactide (LA) and 2‐methyl‐2‐benzoxycarbonyl‐propylene carbonate (MBC) and subsequent catalytic hydrogenation. The pendant carboxyl groups of the copolymer MPEG‐b‐P(LA‐co‐MCC) were conjugated with antitumor drug docetaxel and tripeptide arginine‐glycine‐aspartic acid (RGD), respectively. ¹H‐NMR spectra confirmed the structure of the copolymer MPEG‐b‐P(LA‐co‐MCC/docetaxel) and MPEG‐b‐P(LA‐co‐MCC/RGD). In vitro antitumor assay indicates that the MPEG‐b‐P(LA‐co‐MCC/docetaxel) conjugate shows high cytotoxic activity against HeLa cancer cells. Cell adhesion and spreading experiment shows that copolymer MPEG‐b‐P(LA‐co‐MCC/RGD) is of benefit to cell adherence and is a promising biodegradable material for cell and tissue engineering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Syntheses of poly(lactic acid)‐poly(ethylene glycol) serial biodegradable polymer materials via direct melt polycondensation and their characterization

Directly starting from lactic acid (LA) and poly(ethylene glycol) (PEG), biodegradable material polylactic acid‐polyethylene glycol (PLEG) was synthesized via melt copolycondensation. The optimal synthetic conditions, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, LA stereochemical configuration, feed weight ratio m_LA/m_PEG and M_n of PEG, were all discussed in detail. When D ,L ‐LA and PEG (M_n = 1000 Da) prepolymerized together as feed weight ratio m_{D ,l‐LA}/m_PEG = 90/10, 15 h copolycondensation under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave D ,L ‐PLEG1000 with the highest [η] of 0.40 dL/g, and the corresponding MW was 41,700 Da. Using L ‐LA instead of D ,L ‐LA, 10 h polymerization under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave L ‐PLEG1000 with the highest [η] of 0.21 dL/g and MW of 15,600 Da. Serial D ,L ‐PLEG with different feed weight ratio and M_n of PEG were synthesized via the simple and practical direct melt copolycondensation, and characterized with FTIR, ¹H NMR, GPC, DSC, XRD, and contact angle testing. D ,L ‐PELG not only had higher MW than PDLLA, PLLA and L ‐PELG, but also better hydrophilicity than PDLLA. The novel one‐step method could be an alternative route to the synthesis of hydrophilic drug delivery carrier PLEG instead of the traditional two‐step method using lactide as intermediate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 577–587, 2006     

Syntheses of poly(lactic acid‐co‐glycolic acid) serial biodegradable polymer materials via direct melt polycondensation and their characterization

The optimal synthetic conditions of poly(lactic acid‐co‐glycolic acid) (PLGA) via melt copolycondensation directly from L ‐lactic acid (L ‐LA) and glycolic acid (GA) with a feed molar ratio of 50/50 are discussed; the important drug‐delivery carrier PLGA50/50 is used as a special example. With reaction conditions of 165°C and 70 Pa and with 0.5 wt % SnCl₂ as the catalyst, 10 h of polymerization gave the L ‐PLGA50/50 with the biggest intrinsic viscosity ([η]), 0.1993 dL/g. The optimal synthetic conditions were verified by the synthesis of D,L ‐PLGA50/50 with D,L ‐lactic acid (D,L ‐LA) instead of L ‐LA, but the biggest [η] was 0.2382 dL/g. Under the same synthetic conditions with L ‐LA and D,L ‐LA as starting materials, serial PLGA with different molar feed ratios, including 100/0, 90/10, 70/30, 50/50, 30/70, 10/90, and 0/100, were synthesized via simple and practical direct melt copolycondensation, and their solubilities were investigated. When the glycolic acid feed molar percentage was equal to or more than 70%, solubilities in tetrahydrofuran and CHCl₃ became worse, and some samples were even wholly insoluble. These biodegradable polymers were also systematically characterized with gel permeation chromatography, Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, differential scanning calorimetry, and X‐ray diffraction. PLGA synthesized from L ‐LA and D,L ‐LA had many differences in weight‐average molecular weight (M_w), glass‐transition temperature, crystallinity, and composition. When the molar feed ratio of LA to GA was 50/50, both the [η] and M_w values of D,L ‐PLGA were higher than those of L ‐PLGA. With D,L ‐LA as the starting material, the structure of the PLGA copolymer was relatively simple, and its properties were apt to be controlled by its GA chain segment. When the feed molar percentage of the monomer (LA or GA) was more than or equal to 90%, the copolymer was apt to be crystalline, and the aptness was more obvious for the L ‐LA monomer. The composition percentage of GA in PLGA was not only higher than the feed molar percentage of GA, but also, the GA percentage in D,L ‐PLGA was higher than in L ‐PLGA. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 244–252, 2006     

Synthesis,thermal degradation,and flame retardance of novel triazine ring‐containing macromolecules for intumescent flame retardant polypropylene

Two novel triazine ring‐containing macromolecules, designated as charring‐foaming agent 1 (CFA1) and charring‐foaming agent 2 (CFA2), were synthesized by a series of polycondensation reactions. Their chemical structures were analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (¹³C solid‐state NMR), and elemental analysis, and their thermal degradation properties were assessed by thermogravimetric analysis (TGA). TGA data revealed that CFA1 and CFA2 show high thermal stability and have a high propensity for char formation, their initial decomposition temperatures being 300.2°C and 287.1°C, and their char residues at 800°C amounting to 32.2 wt % and 21.1 wt %, respectively. CFA1 presents higher thermal stability and more char residue than CFA2. Based on experimental results of the flame retardancy (limiting oxygen indices values and UL‐94 V‐0 rating) and the TG data of new intumescent flame retardant polypropylene (IFR‐PP) containing CFA1 and CFA2, CFA1 exhibits more outstanding intumescent flame retardance than CFA2. IFRs containing CFA1 and CFA2 enhanced Notched Izod Impact strength of IFR‐PP, and slightly lower tensile strength of IFR‐PP. IFR2 shows more advantageous effect on mechanical properties of IFR‐PP than IFR1. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of degradable copoly(trans‐4‐hydroxy‐L‐proline/ϵ‐caprolactone)

The melt polycondensation reaction of N‐protected trans‐4‐hydroxy‐L ‐proline (N‐Z‐Hpr) and ?‐caprolactone (?‐CL) over a wide range of molar fractions in the feed produced new and degradable poly(N‐Z‐Hpr‐co‐?‐CL)s with stannous octoate as a catalyst. The optimal reaction conditions for the synthesis of the copolymers were obtained with 1.5 wt % stannous octoate at 140°C for 24 h. The synthesized copolymers were characterized by IR spectrophotometry, ¹H NMR, differential scanning calorimetry, and Ubbelohde viscometry. The values of the inherent viscosity (η_inh) and glass‐transition temperature (T_g) of the copolymers depended on the molar fractions of N‐Z‐Hpr. With an increase in the trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) feed from 10 to 90 mol %, a decrease in η_inh from 2.47 to 1.05 dL/g, and an increase in T_g from ?48 to 49°C were observed. The in vitro degradation of these poly(N‐CBz‐Hpr‐co‐?‐CL)s was evaluated from weight‐loss measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3176–3182, 2003     

Synthesis and chain extension of poly(L‐lactic acid‐co‐succinic acid‐co‐1,4‐butene diol)

L ‐Lactic acid (LA) was copolymerized with succinic acid (SA) and 1,4‐butenediol (1,4‐BED) in bulk state with titanium(IV) butoxide as a catalyst to produce poly(LA‐co‐SA‐co‐1,4‐BED) (PLASBED). Poly(L ‐lactic acid) (PLLA) homopolymer obtained from a direct condensation polymerization of LA had weight average molecular weight (M_w) less than 4.1 × 10⁴ and was too brittle to prepare specimens for the tensile test. Addition of SA and 1,4‐BED to LA produced PLASB with M_w as high as 1.4 × 10⁵ and exhibited tensile properties comparable to a commercially available high‐molecular‐weight PLLA. Chain extension by intermolecular linking reaction through the unsaturated 1,4‐BED units in PLASBED with benzoyl peroxide further increased the molecular weight and made PLASBED more ductile and flexible to show elongation at break as high as 450%. Biodegradability of PLASBED measured by the modified Sturm test was nearly independent of the 1,4‐BED content. Gel formation during the chain extension did not exert any significant influence on the biodegradability either. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1116–1121, 2005     

Synthesis and characterization of poly(L‐lactide‐co‐ϵ‐caprolactone)‐b‐poly(L‐lactide) biodegradable diblock copolyesters: Effect of the block lengths on their thermal properties

Poly(L ‐lactide‐co‐ε‐caprolactone)‐b‐poly(L ‐lactide) [P(LL‐co‐CL)‐b‐PLL] diblock copolyesters were synthesized in a two‐step process with 1‐dodecanol (DDC) and stannous octoate as the initiating system. In the first‐step reaction, a 50:50 mol % amorphous poly(L ‐lactide‐co‐ε‐caprolactone) [P(LL‐co‐CL)] copolyester was synthesized via the bulk copolymerization of L ‐lactide and ε‐caprolactone, which was followed by the polymerization of the PLL crystalline block at the end chain in the second‐step reaction. The yielded copolyesters were characterized with dilute‐solution viscometry, gel permeation chromatography, ¹H‐ and ¹³C‐NMR, and differential scanning calorimetry methods. The molecular weights of the P(LL‐co‐CL) copolyesters from the first‐step reaction were controlled by the DDC concentrations, whereas in the second‐step reaction, the molecular weights of the P(LL‐co‐CL)‐b‐PLL diblock copolyesters depended on the starting P(LL‐co‐CL) copolyester molecular weights and L ‐lactide/prepolymer molar ratios. The starting P(LL‐co‐CL) copolyester molecular weights and PLL block lengths seemed to be the main factors affecting specific thermal properties, including the melting temperature (T_m), heat of melting (ΔH_m), crystallizing temperature (T_c), and heat of crystallizing (ΔH_c), of the final P(LL‐co‐CL)‐b‐PLL diblock copolyester products. T_m, ΔH_m, T_c, and ΔH_c increased when the PLL block lengths increased. However, these thermal properties of the diblock copolyesters also decreased when the P(LL‐co‐CL) block lengths increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Poly(para‐dioxanone)/poly(D,L‐lactide) blends compatibilized with poly(D,L‐lactide‐co‐para‐dioxanone)

The effect of poly(D ,L ‐lactide‐co‐para‐dioxanone) (PLADO) as the compatibilizer on the properties of the blend of poly(para‐dioxanone) (PPDO) and poly(D ,L ‐lactide) (PDLLA) has been investigated. The 80/20 PPDO/PDLLA blends containing from 1% to 10% of random copolymer PLADO were prepared by solution coprecipitation. The PLADO component played a very important role in determining morphology, thermal, mechanical, and hydrophilic properties of the blends. Addition of PLADO into the blends could enhance the compatibility between dispersed PDLLA phase and PPDO matrix; the boundary between the two phases became unclear and even the smallest holes were not detected. On the other hand, the position of the T_g was composition dependent; when 5% PLADO was added into blend, the T_g distance between PPDO and PDLLA was shortened. The blends with various contents of compatibilizer had better mechanical properties compared with simple PPDO/PDLLA binary polymer blend, and such characteristics further improved as adding 5% random copolymers. The maximum observed tensile strength was 29.05 MPa for the compatibilized PPDO/PDLLA blend with 5% PLADO, whereas tensile strength of the uncompatibilized PPDO/PDLLA blend was 14.03 MPa, which was the lowest tensile strength. © 2010 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

From 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     

Flame‐retardancy properties of tris(2‐hydroxyethyl) isocyanurate based charring agents on polypropylene

Tris(2‐hydroxyethyl) isocyanurate based charring agent (TBCA) was synthesized by melt polycondensation with tris(2‐hydroxyethyl) isocyanurate (THEIC) and terephthalic acid as raw materials. It was characterized by Fourier transform infrared spectroscopy, elemental analysis, ¹H‐NMR, and thermogravimetric analysis (TGA). TBCA was blended with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The charring properties of TBCA was tested by flame retardancy in the PP/APP/TBCA (PP/IFR₂) composite and compared with that of the PP/APP/THEIC (PP/IFR₁) composite. The results show that PP/IFR₂ had lower flame‐retardant properties but better water resistance than that of the PP/IFR₁ composite because PP/IFR₂ could still obtain a V‐0 rating after it had been soaked in water at 70°C for 96 h, whereas PP/IFR₁ could not achieve any rating after 36 h. Their combustion performance was further evaluated by a cone calorimeter test, their thermal degradation processes were studied by TGA, and the morphology of the char residue was observed by scanning electron microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41810.     

Preparation of high‐molecular‐weight poly(L‐lactic acid)‐based polymers through direct condensation polymerization in bulk state

Poly(L ‐lactic acid‐co‐succinic acid‐co‐1,4‐butanediol) (PLASB) was synthesized by a direct condensation copolymerization of L ‐lactic acid, succinic acid (SA), and 1,4‐butanediol (BD) in bulk state using titanium(IV) butoxide (TNBT) as a catalyst. Weight average molecular weight (M_w) of PLASB increased from 3.5 × 10⁴ to 2.1 × 10⁵ as the content of SA and BD went up from 0.01 to 0.5 mol/100 mol of L ‐lactic acid (LA). PLASB having M_w in the range from 1.8 × 10⁵ to 2.1 × 10⁵ showed tensile properties comparable to those of commercially available poly(L ‐lactic acid) (PLLA). In sharp contrast, homopolymerization of LA in bulk state produced PLLA with M_w as low as 4.1 × 10⁴, and it was too brittle to prepare specimens for the tensile tests. M_w of PLASB synthesized by using titanium(IV)‐2‐ethyl(hexoxide), indium acetate, indium hydroxide, antimony acetate, antimony trioxide, dibutyl tin oxide, and stannous‐2‐ethyl 1‐hexanoate was compared with that of PLASB obtained by TNBT. Ethylene glycol oligomers with different chain length were added to LA/SA in place of BD to investigate effect of chain length of ethylene glycol oligomers on the M_w of the resulting copolymers. Biodegradability of PLASB was analyzed by using the modified Sturm test. Toxicity of PLASB was evaluated by counting viable cell number of mouse fibroblast cells that had been in contact with PLASB discs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 466–472, 2006     

Development of a DOPO‐containing melamine epoxy hardeners and its thermal and flame‐retardant properties of cured products

In this study, a novel Schiff base of melamine used as flame‐retardant curing agent for epoxy resins, was synthesized via condensation reaction of 4‐hydroxybenzaldehyde with melamine, followed by the addition of 9,10‐dihydro‐9‐oxa‐10‐phosphaphen‐anthrene 10‐oxide (DOPO) to the resulting imine linkage. The structure of DOPO‐containing melamine Schiff base (P‐MSB) was characterized by Fourier transformed infrared spectroscopy, ¹H‐nuclear magnetic resonance (¹H‐NMR) and ³¹P‐NMR. The compound (P‐MSB) was used as a reactive flame retardant in o‐cresol formaldehyde novolac epoxy resin (CNE) to prepare flame‐retardant epoxy resins for electronic application. The thermal and flame‐retardant properties of the epoxy resins cured by various equivalent ratios phenol formaldehyde novolac (PN) and P‐MSB were investigated by the nonisothermal differential scanning calorimetry, the thermogravimetric analysis, and limiting oxygen index test. The obtained results showed that the cured epoxy resins possessed high T_g (165°C) and good thermal stability (T_5%, 321°C). Moreover, the P‐MSB/CNE systems exhibited higher limiting oxygen index (35) and more char was maintained in P‐MSB/CNE systems than that in PN/CNE system and the effective synergism of phosphorus–nitrogen indicated their excellent flame retardancy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Glass transition and mechanical properties of PLLA and PDLLA‐PGA copolymer blends

The change of the glass transition temperatures (T_g) in the blend of poly(L ‐lactic acid) (PLLA) and the copolymers of poly(D,L ‐lactic acid) and poly(glycolic acid) (PDLLA‐PGA) with different D,L ‐lactic acid and glycolic acid composition ratio (50 : 50, 65 : 35, and 75 : 25) was studied by DSC. Dynamic mechanical measurement and tensile testing were performed at various temperatures around T_g of the blend. In the blend of PLLA and PDLLA‐PGA50 (composition ratio of PDLLA and PGA 50 : 50), T_g decreased from that of PLLA (about 58°C) to that of PDLLA‐PGA50 (about 30°C). A single step decrease was observed in the DSC curve around T_g between the weight fraction of PLLA (W(PLLA)) 1.0 and 0.7 (about 52°C) but two‐step changes in the curve are observed between W(PLLA) = 0.6 and 0.3. The T_g change between that of PLLA and that of PDLLA‐PGA and the appearance of two T_gs suggest the existence of PLLA rich amorphous region and PDLLA‐PGA copolymer rich amorphous region in the blend. A single step decrease of E′ occurs at around T_g of the pure PLLA but the two‐step decrease was observed at W(PLLA) = 0.6 and 0.4, supporting the existence of the PLLA rich region and PDLLA‐PGA rich region. Tensile testing for various blends at elevated temperature showed that the extension without yielding occurred above T_g of the blend. Partial miscibility is suggested for PLLA and PDLLA‐PGA copolymer blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2164–2173, 2004     

Ring‐opening graft polymerization of L‐lactide onto starch granules in an ionic liquid

A room temperature ionic liquid 1‐allyl‐3‐methylimidazolium chloride ([AMIM]Cl) was a promising direct solvent for starch and nonderivitizing solvent for starch‐effective dissolution, in which the ring‐opening graft polymerization (ROGP) of L ‐lactide (L ‐LA) onto starch chains was carried out homogeneously. The obtained starch grafted poly(L ‐lactide) (starch‐g‐PLLA) was characterized by FTIR, ¹³C NMR, DSC, and WAXD, and the good adhesion between the two components was evidenced by SEM observations although the chains of grafted PLLA were not long. The grafting efficiency of PLLA reached 30% when the ROGP proceeded at 100°C for 10 h with L ‐LA/starch 0.5 : 1 (wt/wt) and stannous octoate (Sn(Oct)₂) as a catalyst, which was calculated according to a standard curve newly created by FTIR method. The homopolymerization of L ‐LA and the disconnection of grafted PLLA from starch‐g‐PLLA were the main competition reactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of an amphiphilic hyperbranched poly(amine‐ester)‐co‐D,L‐lactide (HPAE‐co‐PLA) copolymers and their nanoparticles for protein drug delivery

A series of hyperbranched poly(amine‐ester)‐co‐D ,L ‐lactide (HPAE‐co‐PLA) copolymer were synthesized by ring‐opening polymerization of D ,L ‐lactide with Sn(Oct)₂ as catalyst to a fourth generation branched poly(amine‐ester) (HPAE‐OHs4). The chemical structures of copolymers were determined by FTIR, ¹H‐NMR, ¹³C‐NMR, and TGA. Double emulsion (DE) and nanoprecipitation (NP) method were used to fabricate the nanoparticles of these copolymers encapsulating bovine serum albumin (BSA) as a model. DSC thermo‐grams indicated that the nanoparticles with BSA kept stable below 40°C. Different factors which influence on particular size and encapsulation efficiency (EE) were investigated. Their EE to BSA could reach 97.8% at an available condition. In vitro release behavior of NPs showed a continuous release after a burst release. The stability maintenance of BSA in the nanoparticle release in vitro was also measured via circular dichroism and fluorescence spectrometry. The results showed that the copolymer nanoparticles have a promising potential in protein delivery system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of alkaline anion exchange membrane with semi‐interpenetrating polymer networks based on poly(vinylidene fluoride‐co‐hexafluoropropylene)

Alkaline anion exchange membrane with semi‐interpenetrating polymer network (s‐IPN) was constituted based upon quaternized poly(butyl acrylate‐co‐vinylbenzyl chloride) (QPBV) and poly(vinylidene fluoride‐co‐hexafluoropropylene) [P(VDF‐HFP)]. The QPBV was synthesized via the free radical copolymerization, followed by quaternization with N‐methylimidazole. The s‐IPN system was constituted by melting blend of QPBV and P(VDF‐HFP), and then crosslinking of P(VDF‐HFP). Ion exchange capacity, water uptake, mechanical performance, and thermal stability of these membranes were characterized. TEM showed that alkaline anion exchange membrane exhibited s‐IPN morphology with microphase separation. The fabricated s‐IPN membrane exhibited hydroxide ion conductivity up to 15 mS cm^?1 at 25 °C and a maximum DMFC power density of 46.55 mW cm^?2 at a load current density of 98 mA cm^?2 at 30 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45775.     

Synthesis and characterization of amphiphilic block polymers with amino groups and their conjugates with folic acid and fluorescent probes

Amphiphilic amino‐bearing biodegradable copolymers, [methoxy‐poly(ethylene glycol)]‐block‐poly[(L ‐lactide)‐co‐(serinol carbonate)] (mPEG‐block‐P(LA‐co‐CA)), are prepared by synthesizing amino‐bearing cyclic carbonate monomer N‐benzoxycarbonylserinol carbonate (CAB) starting from serinol, by ring‐opening polymerization of L ‐lactide and CAB using diethylzinc as catalyst and mPEG as macroinitiator, and by subsequent removal of the protective benzyloxycarbonyl groups by HBr treatment. After deprotection, the pendant amino groups on the carbonate units are reacted with N‐hydroxylsuccinimide‐activated folic acid (FA) to achieve mPEG‐block‐P(LA‐co‐CA/FA) conjugate and with fluorescein isothiocyanate (FITC) to achieve mPEG‐block‐P(LA‐co‐CA/FITC) conjugate. The structures of mPEG‐block‐P(LA‐co‐CAB), mPEG‐block‐P(LA‐co‐CA), mPEG‐block‐P(LA‐co‐CA/FA) and mPEG‐block‐P(LA‐co‐CA/FITC) are confirmed using ¹H NMR and Fourier transform infrared spectroscopy. The block copolymers can self‐assemble into micelles in aqueous solution. Because of the functionality of FA and FITC, these copolymers can find important applications in drug delivery systems to serve as targeting moieties and fluorescent probes. Copyright © 2011 Society of Chemical Industry     

Synergistic effect of THEIC‐Based charring agent on flame retardant properties of polylactide

A novel charring agent tris(2‐hydrooxyethyl) isocyanurate terephthalic acid ester, tetramer (TT4) was synthesized using tris(2‐hydrooxyethyl) isocyanurate and terephthalic acid as raw materials, and it was characterized by Fourier transformed infrared spectrometry and ¹H‐NMR spectrum. It was combined with ammonium polyphosphate (APP) to form intumescent flame retardants for polylactide (PLA). The combustion properties and thermal stability of PLA/APP/TT4 composites were evaluated by UL‐94 burning tests, limiting oxygen index (LOI), and thermogravimetric analyses (TGA). It was found PLA with 30 wt % of APP/TT4 (5 : 1) achieved UL‐94 V‐0 rating and a 40.6 LOI value. Results from TGA demonstrated that APP/TT4 composites could retard the degradation of PLA above 410°C. The char residue at 500°C is higher than 24%, showing a good char forming ability. Moreover, the continuous and expansionary char layer observed from the SEM images proved good charring forming ability of TT4. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41218.