One‐pot regioselective and stereoselective terpolymerization of rac‐lactide,CO2 and rac‐propylene oxide with TPPMCl (M = Cr,Co, Al)/PPNCl binary catalyst

Tetraphenyl porphyrin metal compound (TPPMCl) (where the TPPMCl was TPPCrCl, TPPCoCl, TPPAlCl), in combination with cocatalyst PPNCl (bis(triphenylphosphine)iminium chloride, the molar ratio of TPPMCl to PPNCl was 1:0.5), was used to catalyze the polymerization of racemic lactide (rac‐LA) in racemic propylene oxide (rac‐PO) medium and the terpolymerization of rac‐LA, CO₂ and rac‐PO. It was found that these TPPMCl/PPNCl binary catalysts could initiate the stereoselective polymerization of rac‐LA in rac‐PO medium to form enriched isotactic polylactide (PLA) (P_i ≥ 68.0%) and terpolymerization of CO₂, rac‐LA, rac‐PO to form PPC‐PLA‐PPO (PPC, poly(propylene carbonate); PPO, poly(propylene oxide)) multiblock copolymer. In particular the PPC‐PLA‐PPO multiblock copolymer thus formed displayed high regioregularity and stereoregularity, and has high head‐to‐tail structure content in the PPC block (H‐T% ≥ 63.6%) and high isotacticity in the PLA block (P_i ≥ 64.0%). The influence of catalyst formula, the monomer feeding ratio, reaction temperature, carbon dioxide pressure and reaction time on the terpolymerization was investigated by ¹H NMR, ¹³C NMR, gel permeation chromatography, DSC and TGA. © 2018 Society of Chemical Industry     

Kinetics of the ring‐opening polymerization of D,L‐lactide using zinc (II) octoate as catalyst

The kinetics of ring‐opening polymerization of D ,L ‐lactide with 2‐ethylhexanoic acid zinc (II) salt as catalyst and methanol as co‐catalyst at different temperatures is investigated. A previously proposed kinetic model accounting for reactions such as activation, propagation, chain transfer, transesterification and thermal non‐radical random chain scission has been applied to simulate the experimental results of conversion and average molecular weights. The relevance of some side reactions, mainly transesterifications and chain scission, has been verified all over the studied temperature range and the corresponding rate constants have been estimated. Copyright © 2011 Society of Chemical Industry     

Synthesis,characterization and catalytic activity of zinc complex for ring‐opening polymerization of lactide

In the present study, salicylaldimine zinc complex (Zn‐HMBED) was synthesized and its reactivity for the ring‐opening polymerization (ROP) of lactide was studied. The zinc complex was prepared by the reaction of zinc solution with one molar equivalent of salicylaldimine Schiff base ligand in methanol under a nitrogen atmosphere. Further, the complex was characterized by various spectroscopic methods, which showed tetrahedral geometry. X‐ray diffraction studies were used for the structure determination of the Schiff base. It was observed that the zinc complex is highly active towards the ROP of lactide. The rate of polymerization is heavily dependent on the initiator used. The zinc complex allows controlled ROP as revealed by the linear relationship between the percentage conversion and the number‐average molecular weight. Finally, a mechanism for the ROP of lactide is proposed by use of the above zinc complex. © 2016 Society of Chemical Industry     

Synthesis of high molecular weight polyoxyethylene with a quaternary catalyst and study of its conductive blends with poly(2‐vinyl pyridine)

High molecular weight polyoxyethylene (PEO) was synthesized by using a quaternary catalyst composed of triisobutyl aluminum, phosphoric acid, water, and N,N‐dimethylaniline (DMA). Optimum synthesis conditions and some properties of the product were studied. This catalyst showed high activity and the molecular weight of the polyoxyethylene obtained can approach one million. The activity of polymerization mainly depends upon the composition of catalyst. The optimum composition is as follows: i‐Bu₃Al:H₃PO₄:H₂O:DMA = 1 : 0.17 : 0.17 : 0.10–0.15 (molar ratio).The active centers of the catalyst was thus proposed. The high molecular weight PEO synthesized by this catalyst was blended with poly(2‐vinyl pyridine) (PVP) and then doped with LiClO₄ and TCNQ to obtain a conductive elastomeric material. Ionic, electronic, and mixed (ionic–electronic) conductivities of blends were investigated. At a Li/EO molar ratio of 0.1 and a TCNQ/VP molar ratio of 0.5, the mixed conductivity of the blend of PEO/PVP/LiCIO₄/TCNQ is higher than the sum of ionic conductivity of PEO/PVP/LiCIO₄ and electronic conductivity of PEO/PVP/TCNQ, when the weight ratio of PEO to PVP is 6/4 or 5/5. It can reach 4 × 10^?6 S/cm at room temperature. Differential scanning calorimetry, thermal gravimetric analysis, and the appearance of the blend showed that both TCNQ and LiClO₄ can complex with PEO and PVP, thus enhancing the compatibility between PEO and PVP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of novel biodegradable poly(carbonate‐co‐phosphate)s

A series of aliphatic poly(carbonate‐co‐phosphate)s was synthesized in bulk using aluminium isopropoxide as initiator by ring‐opening polymerization with various cyclic carbonates (trimethylene carbonate (TMC) and 5,5‐dimethyltrimethylene carbonate (DTC)) and cyclic phosphates (ethylene ethyl phosphate (EEP), ethylene isobutyl phosphate (EIBP), ethylene lauryl phosphate (ELP) and ethylene stearyl phosphate (ESP)). The influence of reaction conditions such as polymerization time, polymerization temperature and initiator concentration on the yield and molecular weight were investigated. The substituent effect of the cyclic monomers on the polymerization was also studied, and the results indicate that the substituents exert a marked influence on the molecular weight of the copolymers obtained. The comonomer reactivity ratios were determined (TMC 0.88 and EEP 1.17). The copolymers with backbone chains rich in phosphate content exhibit better hydrophilicity than that of TMC homopolymer, and the degradation rate of the copolymers increases with the increase of phosphate content therein. © 2001 Society of Chemical Industry     

Synthesis of star‐shaped poly(ε‐caprolactone)‐b‐poly(L‐lactide) copolymers: From star architectures to crystalline morphologies

Hexa‐armed star‐shaped poly(ε‐caprolactone)‐block‐poly(L ‐lactide) (6sPCL‐b‐PLLA) with dipentaerythritol core were synthesized by a two‐step ring‐opening polymerization. GPC and ¹H NMR data demonstrate that the polymerization courses are under control. The molecular weight of 6sPCLs and 6sPCL‐b‐PLLAs increases with increasing molar ratio of monomer to initiator, and the molecular weight distribution is in the range of 1.03–1.10. The investigation of the melting and crystallization demonstrated that the values of crystallization temperature (T_c), melting temperature (T_m), and the degree of crystallinity (X_c) of PLLA blocks are increased with the chain length increase of PLLA in the 6sPCL‐b‐PLLA copolymers. On the contrary, the crystallization of PCL blocks dominates when the chain length of PLLA is too short. According to the results of polarized optical micrographs, both the spherulitic growth rate (G) and the spherulitic morphology are affected by the macromolecular architecture and the length of the block chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of ABA type tri‐block copolymers derived from p‐dioxanone,L‐lactide and poly(ethylene glycol)

A series of triblock co‐polymers, consisting of a poly(ethylene glycol) (PEG) central block joined to two blocks of random p‐dioxanone‐co‐L ‐lactide copolymers were synthesized by ring‐opening polymerization of p‐dioxanone (PDO) and L ‐lactide (LLA) initiated by PEG in the presence of stannous 2‐ethylhexanoate catalyst. The resulting copolymers were characterized by various techniques including ¹H and ¹³C NMR and FTIR spectroscopies, gel permeation chromatography, inherent viscosity, wide‐angle X‐ray diffractometry (WAXD) and differential scanning calorimetry (DSC). The conversion of PDO and L ‐lactide into the polymer was studied various mole ratios and at different polymerization temperature from ¹H NMR spectra. Results of WAXD and DSC showed that the crystallinity of PEG macroinitiator was greatly influenced by the composition of PDO and L ‐lactide in the copolymer. The triblock copolymers with low molecular weight were soluble in water at below room temperature. © 2003 Society of Chemical Industry     

Visible light‐absorbing biocompatible polymers based on L‐lactide and aminosugars: preparation and characterization

Two series of polymers with low‐molecular‐weight L ‐lactide side‐arms were prepared by ring‐opening polymerization using D ‐glucosamine and N‐acetyl‐D ‐glucosamine as polymer core molecules, and methanesulfonic acid as solvent and catalyst. This simple synthetic route does not rely on the use of organometallic catalysts, and has also proven useful to the authors for chitosan grafting with lactones. NMR spectroscopy reveals a high degree of substitution (>3), and Fourier transform infrared/NMR spectra suggest the existence of three different lactate tautomers likely to be responsible for coloration. These D ‐glucosamine‐based polymers also display glass transition temperatures approximately 10 °C above that of the human body, which points to the potential of these lactone‐grafted aminosugars with tunable amphiphilic character in the design of submicrometer‐sized drug delivery vehicles. They are also viewed as interesting hydrophobic chelating agents for catalytic transition metal centers. Copyright © 2010 Society of Chemical Industry     

Kinetics study of Ti[O(CH2)4OCHCH2]4 initiated ring‐opening polymerization of ε‐caprolactone by differential scanning calorimetry

Chemical shrinkage was used for the in situ measurement of the progressing chemical stabilization reactions and the influence of ozone during the stabilization of polyacrylonitrile. A method for evaluating the activation energy through the sensitivity temperature is presented. The calculated results show that the activation energies were 161.57 kJ/mol in air and 181.23 kJ/mol in ozone-enriched air. Therefore, the chemical reactions were postponed during stabilization in ozone-enriched air. Ozone seemed to act in three ways: first, ozone promoted the formation of the serious skin–core structure. Second, ozone accelerated the chemical reactions and shortened the stabilization time at lower heating rates. Third, ozone postponed the chemical reactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and dispersibility of poly(L‐lactide)‐grafted silica nanoparticle

To improve dispersibility of silica nanoparticle in organic solvents, the grafting of poly(L ‐lactide) (PLLA) onto silica nanoparticle surface by ring‐opening polymerization of L‐lactide (LA) was investigated in the presence of an amidine base catalyst. The ring‐opening polymerization of LA successfully initiated in the presence of silica having amino groups (silica‐NH₂) and an amidine base catalyst to give PLLA‐grafted silica, but not in the presence of untreated silica (silica‐OH). In the absence of the amidine base catalyst no ring‐opening polymerization of LA even in the presence of silica‐NH₂ and no grafting of PLLA onto silica were observed. It became apparent that the amidine base catalyst acts as an effective catalyst for the ring‐opening graft polymerization of LA from the surface of silica‐NH₂. In addition, it was found that the percentage of PLLA grafting onto silica could be controlled according to the reaction conditions. The average particle size of PLLA‐grafted silica was smaller than that of silica‐NH₂. Therefore, it was considered that the aggregation structure of silica nanoparticles was considerably destroyed by grafting of PLLA onto the surface. The PLLA‐grafted silica gave a stable dispersion in polar solvents, which are good solvents for PLLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Controlled and stereospecific polymerization of rac‐lactide with a single‐site ethyl aluminum and alcohol initiating system

A single‐site ethyl aluminum complex, [2,2‐ diethyl‐1,3‐propylenebis(3,5‐di‐tert‐butyl‐salicylideneiminato)] ethyl aluminum (2), with a geminal diethyl substitutent on the diamino bridge was synthesized by the reaction of AlEt₃ with 1 equiv of N,N′‐(2,2‐diethyl‐1,3‐propylene)bis(3,5‐di‐tert‐butylsalicylideneimine). X‐ray diffraction showed that complex 2 contained a five‐coordinate aluminum atom with a distorted trigonal bipyramidal geometry in the solid state. ¹H‐NMR and ¹³C‐NMR spectra indicated that the two conformational enantiomers of 2 tautomerized quickly on the NMR timescale in solution. In the presence of isopropyl alcohol, the ring‐opening polymerization (ROP) of rac‐lactide with complex 2 produced a crystalline stereoblock polylactide (PLA). The stereoblocks contained an average of 12 units (L? = 12) of enantiomerically pure lactic acid. There was a linear relationship between the monomer conversion and number‐average molecular weights of the polymer. An induction period was observed for the polymerization. The induction period increased with decreasing concentration of catalyst 2 and isopropyl alcohol. In the presence of poly(ethylene glycol) (PEG), a PLA/PEG/PLA stereocomplex was prepared directly by the ROP of rac‐lactide with complex 2, which was confirmed by NMR, gel permeation chromatography, wide‐angle X‐ray diffraction, and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 102–108, 2005     

Synthesis and characterization of biodegradable block copolymer pluronic‐b‐poly(L‐lysine)

This study presented the investigations on the synthesis of a novel biodegradable block copolymer of pluronic‐b‐poly(L ‐lysine) (pluronic‐b‐PLL), which combined the characteristics of aliphatic polyester and poly(amino acids). The synthesis work started with end‐capping of pluronic with N‐t‐butoxycarbonyl‐L ‐phenylalanine using dicyclohexylcarbodiimide in the presence of 4‐dimethylaminopyridine, followed by a deprotection process to obtain the amino‐terminated pluronic; the new primary amino group in the modified pluronic initiated ring‐opening polymerization of amino acid N‐carboxyanhydride, which afforded the pluronic‐b‐poly(N^ε‐(Z)‐L ‐lysine) block copolymer. Finally, removal of the side‐chain N^ε‐(carbonybenzoxy) end protecting groups yields the block copolymer of pluronic‐b‐PLL. The products were characterized by ¹H‐NMR, FTIR, DSC, and GPC. The block copolymer micelle containing the anticancer drug paclitaxel was prepared by the double emulsion method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of poly(propylene carbonate) from highly active,inexpensive achiral (Salph)Co(III)X as initiator and bis(triphenyl phosphine) iminium as co‐initiator

Copolymerization of carbon dioxide with racemic propylene oxide has been investigated in the presence of an inexpensive achiral (Salph)Co(III)X [Salph is N,N′‐bis(3,5‐di‐tert‐butylsalicylidene) phenylenediimine and X is pentaflorobenzoate] as initiator and [PPN]⁺Cl^? ([PPN] is bis(triphenylphosphine) iminium) as co‐initiator. Effects of monomer‐to‐initiator ratio, initiator/co‐initiator ratio, and reaction conditions like stirring rate, temperature, and pressure of CO₂ on the molecular weight, yield, and selectivity of poly(propylene carbonate) over propylene carbonate have been studied. The initiator used in the study has been found to be highly active at milder conditions of pressure and temperature, giving a product with maximum M_w of 14.8 × 10³ g/mol at 25 bar and 50°C. The conversion increases with an increase in stirring rate and then becomes almost constant at 1100 rpm and above, indicating that the reaction is no longer limited by mass transfer. The molecular weight M_w of the polymer has been found to increase with increasing monomer‐to‐initiator ratio up to 3000:1, but it starts decreasing with a further increase in monomer‐to‐initiator ratio, giving a polymer of lower M_w. The activity of the initiator is considerably affected by pressure, temperature, time, and amount of co‐initiator. The polymeric product has low polydispersity (near unity) with negligible formation of polypropylene oxide. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43099.     

Microwave‐irradiated ring‐opening polymerization of D,L‐lactide under atmosphere

Poly(D ,L ‐lactide) (PDLLA) was synthesized by microwave‐irradiated ring‐opening polymerization catalyzed by stannous octoate (Sn(Oct)₂) under atmosphere. The effects of heating medium, monomer purity, catalyst concentration, microwave irradiation time, and vacuum level were discussed. Under the appropriate conditions such as carborundum (SiC) as heating‐medium, 0.15% catalyst, lactide with purity above 99.9%, 450 W microwave power, 30 min irradiation time, and atmosphere, PDLLA with a viscosity–average molecular weight (M_η) over 2.0 × 10⁵ and a yield over 85% was obtained. The dismission of vacuum to ring‐opening polymerization of D ,L ‐lactide (DLLA) under microwave irradiation simplified the process greatly. The temperature under microwave irradiation and conventional heating was compared. The largely enhanced ring‐opening polymerization rate of DLLA under microwave irradiation was the coeffect of thermal effects and microwave effects. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2244–2247, 2006     

Catecholate complexes of zirconium: synthesis,spectroscopic characterization and polymerization studies

Varieties of new catecholate complexes containing zirconium were synthesized in high yields and purity. These derivatives are potent initiators for the ring‐opening polymerization (ROP) of rac‐lactide, l ‐lactide, ?‐caprolactone, δ‐valerolactone, rac‐β‐butyrolactone, ethylene and propylene. The number‐average molecular weights of the resulting polymers are slightly higher than the theoretical molecular weight and they have controlled molecular weight distributions. The isopropoxide moiety in these complexes is responsible for initiating the ROP. For ethylene and propylene polymerization, we were able to achieve good activity using methylaluminoxane as a co‐catalyst. © 2013 Society of Chemical Industry     

Zinc‐based catalyst for the ring‐opening polymerization of cyclic esters

A zinc‐based catalyst zinc bis[bis(trimethylsilyl)amide] was used for the polymerization of cyclic esters including L ‐lactide (L ‐LA) and 2‐methyl‐2‐carboxyl‐propylene carbonate (MBC). The polymerization of L ‐lactide in THF could be carried out successfully under mild conditions in very short time by using the zinc catalyst and alcohols as the initiators. Kinetic study in solution polymerization prooved the polymerization has high monomer conversion degree close to 100% and the molecular weight of the resulting polyester has linear increase with the increase of [M]₀ /[I] (molar ratio of monomer to initiator). Sequential polymerization of L ‐LA and MBC in THF also showed high MBC conversion of 94% with a narrow molecualr weight maintained, indicating a living nature of this polymerization. The zinc catalyst system has also been used for the L ‐LA bulk polymerization with a high monomer conversion. ¹³C NMR indicated the polymer possesses high regioregularity and the minor regioirregular component was owing to the D ‐LA in the monomer inserted into the polymer mainchain during the transesterifcation. Interaction between monomer and zinc catalyst has been found to be a key factor to sustain a homogenous solution during the initiating procedure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of star‐shaped poly(ϵ‐caprolactone) by samarium‐based tetrafunctional initiator and its dilute‐solution properties

An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1‐tetra(2‐bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh₂)₂ and SmI₂] in tetrahydrofuran has proven to initiate the ring‐opening polymerization of ?‐caprolactone (CL) giving star‐shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four‐armed poly(?‐caprolactone) (PCL) was fractionated, and the dilute‐solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10^?2M_w^0.74 and [η] = 1.97 × 10^?2M_w^0.75, respectively. In addition, the unperturbed dimensions of the star‐shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006     

Synthesis of hydrosoluble polymers of oxazoline using Maghnite‐H as catalyst

2,4,4‐Triméthyl‐2‐oxazoline was polymerized, using an acid exchanged montmorillonite clay as catalyst, with the aim to study the influence of the methyl group size in the initiation and propagation processes. The effect of amount of catalyst temperature, time, and solvent on the polymerization yield and viscosity of the polymers were studied. The polymers obtained were characterized by spectrometric methods and their average molecular weights were determined by viscosimetrie and GPC data. The polymers presented similar spectrometric results and narrow molecular weight distributions. The kinetics indicated that the polymerization rate is first order with respect to monomer concentration. The polymerization results showed that the methyl groups present in the monomer affected the initiation process. Mechanism studies showed that polymerization of TMOX involves nucleophilic ring opening by attack of nitrogen to cleave the CH₂? O bond of the oxazoline ring. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1792–1800, 2007     

Synthesis of perfluorohexyl‐terminated poly(ethylene oxide) using maghnite‐h as clay catalyst

Activated monomer cationic ring‐opening polymerization of ethylene oxide initiated with 1H,1H,2H, 2H‐perfluorooctan‐1‐ol, using acid exchanged montmorillonite clay called Maghnite‐H⁺ (Mag‐H⁺) as an effective catalyst, was carried out to obtain the corresponding homopolymers with narrow polydispersity ratios. The molecular weights of the obtained polymers could be controlled with the feed ratio of the monomer and initiator. The effect of amount of catalyst and time on the polymerization yield and viscosity of the polymers were studied. The structure was confirmed by ¹H‐NMR and MALDI‐TOF‐MS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of water soluble poly(N‐acetyl)iminoethylene and poly(ethyleneimine) by ion‐exchanged clay montmorillonite

The cationic polymerization of 2‐méthyl‐2‐oxazoline was carried out at 0°C in acetonitrile using an acid‐exchanged montmorillonite as acid solid ecocatalyst (Maghnite‐H⁺). The effect of the amount of catalyst, solvent, and times of polymerization on yield and viscosity of polymer was studied. A typical reaction product (PMOX) was analyzed by infrared and nuclear magnetic resonance spectroscopy as well as by gel‐permeation chromatography and MALDI‐TOF MS. The polymers presented similar spectrometric results and narrow molecular weight distribution. The poly(N‐acetyl)iminoethylene was hydrolyzed in acid medium obtaining a linear poly(ethyleneimine). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3741–3750, 2006