Cationic Ring Opening Polymerization of Glycolide Catalysed by a Montmorillonite Clay Catalyst

The ring opening bulk polymerization of glycolide catalyzed by Maghnite-H⁺ was reported. Maghnite-H⁺ is a montmorillonite sheet silicate clay, exchanged with protons. The effect of the amount of Maghnite-H⁺ and the temperature on polymerisation was studied. Increasing Maghnite-H⁺ proportion and temperature produced the increase in glycolide conversion. The kinetics indicated that the polymerization rate is first order with respect to monomer concentration. Mechanism studies showed that monomer inserted into the growing chains with the acyl–oxygen bond scission rather than the break of alkyl–oxygen bond.     

Synthesis of copolymer from 1,3,5‐trioxane and 1,3‐dioxolane catalyzed by Maghnite‐H+

Copolymers (polyoxymethylene) were prepared by cationic copolymerization of 1,3,5‐trioxane (TOX) with 1,3‐dioxolane (DOX) in the presence of Maghnite‐H⁺ (Mag‐H⁺) in solution. Maghnite is a Montmorillonite sheet silicate clay, with exchanged protons to produce Mag‐H⁺. Various techniques, including ¹H‐NMR, ¹³C‐NMR, FT‐IR spectroscopy, and Ubbelohde viscometer were used to elucidate structural characteristics properties of the resulting copolymers. The influence of the amount of catalyst, of dioxolane (DOX), temperature, solvent, and time of copolymerization on yield and on intrinsic viscosity of copolymers was studied. The yield of copolymerization depends on the amount of Mag‐H⁺ used and the reaction time. We also propose mechanisms involved in the synthesis of copolymer (polyoxymethylene). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Copolymerization of γ-methacryloxy propyl trimethoxy silane and methyl methacrylate

Copolymerization of methyl methacrylate (MMA) with low mole fractions of γ-methacryloxypropyl trimethoxy silane (MTS) was investigated with an aim to synthesize copolymers which can be cross-linked by hydrolytic cleavage of methoxy groups. Several copolymer samples were prepared by changing the molar ratios of two monomers in the initial monomer feed. Rate of copolymerization depended on the concentration of monomers and increased with an increase in MTS concentration. The copolymers were characterized by infrared (IR) and ¹H nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and intrinsic viscosity determination. The effect of structure on thermal behavior was investigated by using dynamic thermogravimetry in nitrogen atmosphere. An attempt was made to identify products of degradation using mass spectrometry. Copolymers were also hydrolyzed in water and cross-linked. The effect of MTS in copolymers on percentage gel formation was determined.     

Enzyme-catalyzed polymerization and degradation of copolymers prepared from ?-caprolactone and poly(ethylene glycol)

Copolymerizations of ?-caprolactone (CL) with monohydroxyl or dihydroxyl poly(ethylene glycol) (PEG) were successfully performed using Novozyme-435 (immobilized lipase B from Candida antartica) as catalyst. Diblock and triblock copolymers with different compositions were characterized by ¹H NMR, GPC, DSC and X-ray diffraction. The enzymatic copolymerization carried out in toluene presented higher reaction rate and yield than that in bulk. Increasing the [CL]/[EO] feed ratio resulted in increases of molecular weight (M_n) of copolymers. Moreover, the compositions of triblock copolymers were closer to the monomer feed ratios than those of diblock copolymers. The resulting copolymers were all semicrystalline, the crystalline structure being of the PCL type. Solution cast films were allowed to degrade in a pH 7.0 phosphate buffer solution containing Pseudomonas lipase. Weight loss data showed that the introduction of PEG segments to the PCL main chain did not alter the enzymatic degradation of PCL significantly.     

Synthesis, characterization and thermal properties of hexaarmed star-shaped poly(ε-caprolactone)-b-poly(d,l-lactide-co-glycolide) initiated with hydroxyl-terminated cyclotriphosphazene

Hexakis[p-(hydroxymethyl)phenoxy]cyclotriphosphazene was prepared by the reaction of hexachlorocycltriphosphaneze with the sodium salt of 4-hydroxybenzaldehyde and subsequent reduction of aldehyde groups to alcohol groups by using sodium borohydride. Hexaarmed star-shaped hydroxyl-terminated poly(ε-caprolactone) (PCL) were successfully synthesized via ring-opening polymerization of ε-caprolactone (CL) with the above hydroxyl-terminated cyclotriphosphazene initiator and stannous octoate catalyst in bulk. The number-average molecular weight of PCL linearly increased with the molar ratio of monomer to initiator. The star-shaped PCL with hydroxy end groups could be used as a macroinitiator for block copolymerization with d,l-lactide (d,l-LA) and glycolide (GA) using stannous octoate catalyst. IR, ¹H NMR and GPC analysis showed the star-block copolymers were successfully synthesized and the molecular weights and the unit composition of the star-shaped block copolymers were controlled by the molar ratios of d,l-LA and GA monomers to CL. The copolymer presented a two-phase structure, namely, PCL crystalline and d,l-LAGA amorphous domains, which made the copolymer different from linear PCL and star-shaped PCL in crystallinity and thermal behaviors.     

N-PEG’ylation of chitosan via “click chemistry” reactions

N-azidated chitosan was prepared by four different methods: using azidated epichlorohydrin, sodium azide plius sodium nitrite, trifluoromethane sulfonyl azide or imidazole-1-sulfonyl azide hydrochloride. Using the two last reagents, the degree of azidation (DA) of chitosan was up to 40% and 65%, respectively. N-azidated chitosans with DA at about 60% were insoluble in aqueous and common organic solvents but dissolved in 5% LiCl solution in N-methyl-2-pyrrolidone, one of the very few solvents for chitin. Chitosan–methoxy poly(ethylene glycol) derivatives containing triazolyl moiety (chitosan-N-TMPEG comb copolymers) were prepared for the first time by coupling via 1,3-dipolar cycloaddition between pendant azide and end alkyne groups of chitosan and MPEG, respectively. Comb copolymers chitosan-N-TMPEG with degree of substitution (DS) of chitosan equal to DA of chitosan were synthesized at a certain excess of MPEG alkyne reaching DS up to 40%. “Clicking” of MPEG alkyne onto azidated chitosan was successful in binary mixture of water and methylene chloride but failed in 5% LiCl solution in N-methyl-2-pyrrolidone. Significant breakdown of chitosan backbone took place under “clicking” of MPEG in the presence of Cu(II)/ascorbate catalyst resulting in graft copolymers with bimodal MWD. Chitosan-N-TMPEG copolymers contained a certain residual amount of Cu and were soluble in acetate buffer (pH 3.7). Novel comb copolymers were characterized by FT-IR and ¹H NMR spectroscopy, SEC with triple detection, intrinsic viscosity, elemental and functional group analysis.     

Preparation and identification of a soluble copolymer from pyrrole and o-toluidine

A series of copolymers were prepared by chemically oxidative polymerization of pyrrole (PY) and ortho-toluidine (OT) in HCl aqueous medium. The yield, intrinsic viscosity, and solubility of the copolymers were studied by changing the monomer molar ratio. The resulting PY/OT copolymers were identified by FTIR, ¹H–NMR, DSC, and WAXD techniques. The experimental results showed that the oxidative polymerization of pyrrole and o-toluidine is exothermic and the resulting polymers exhibit an enhanced solubility in most organic solvents compared with that of pyrrole homopolymer. The polymer obtained is a real and amorphous copolymer containing pyrrole and o-toluidine units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 510–518, 2001     

Copolymerization of phenylisocyanate and ϵ‐caprolactone with rare earth chloride systems

A copolymer of phenylisocyanate (PhNCO) and ε‐caprolactone (CL) was synthesized by the rare earth chloride systems lanthanide chloride isopropanol complex (LnCl₃·3iPrOH) and propylene epoxide (PO). Polymerization conditions were investigated, such as lanthanides, reaction temperature, monomer feed ratio, La/PO molar ratio, and aging time of catalyst. The optimum conditions were: LaCl₃ preferable, [PhNCO]/[CL] in feed = 1 : 1 (molar ratio), 30°C, [monomer]/[La] = 200, [PO]/[La] = 20, aging 15 min, polymerization in bulk for 6 h. Under such conditions the copolymer obtained had 39 mol % PhNCO with a 78.2% yield, M_n = 20.3 × 10³, and M_w/M_n = 1.60. The copolymers were characterized by GPC, TGA, ¹H‐NMR, and ¹³C‐NMR, and the results showed that the copolymer obtained had a blocky structure with long sequences of each monomer unit. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2135–2140, 2007     

Facile synthesis of oxidative copolymers from aminoquinoline and anisidine

Oxidative copolymerization of 8-aminoquinoline (AQ) and o-anisidine (AS) using ammonium persulfate as oxidant was studied under various polymerization conditions and fine and uniform copolymer particles of several micrometers, determined by laser particle size and atomic force microscopic analyses, were synthesized simply. The polymerization yield, molecular weight, solubility, electroconductivity, and thermostability of the copolymers were systematically studied by changing the comonomer ratio, polymerization temperature, monomer/oxidant ratio, and acidic medium. Single chain configuration of the copolymers with various AQ/AS ratios was simulated and well related to the intrinsic viscosity. The macromolecular structure of the resulting copolymers was wholly characterized by elementary analysis, IR, UV-vis, high-resolution ¹H NMR, and solid-state high-resolution ¹³C NMR. The results show that the oxidative copolymerization of AQ and AS is exothermic. All copolymers are totally soluble in H₂SO₄, HCOOH, m-cresol but their solubility in other solvents depends significantly on the comonomer ratio, and also on the polymerization conditions. The oxidative polymer obtained is a real copolymer containing AQ and AS units rather than a mixture of two homopolymers. The AQ content calculated based on the ¹H NMR spectra of the copolymers is slightly higher than feed AQ content when feed AQ content is lower than 70 mol%. However, the AQ content calculated based on the ¹³C NMR and elementary analyses is lower than the feed AQ content when the AQ feed content is higher than 50 mol%. A peculiar dependency of molecular weight and electroconductivity of the copolymers on the AQ/AS ratio was observed. The decomposition temperature of the copolymers rises with increasing AQ content. Therefore, the thermostability of the copolymers increases with increasing AQ content due to its high aromaticity.     

Copolymerization of styrene with vinyl monomers substituted by nitrile and sulfonyl groups

Two trisubstituted vinyl monomers, 2-phenylsulfonyl (crotonitrile) and 2-phenylsulfonyl (cinnamonitrile) were synthesized and characterized by proton NMR, IR, ¹³C-NMR, and mass spectroscopy. Both monomers were copolymerized with styrene by free-radical initiation. The copolymerization parameters of both systems were determined, and the mutual reactivity of the monomers of the two systems is discussed. The new copolymers were characterized by proton NMR and IR spectroscopy, melting range, T_g, and intrinsic viscosity. The influence of the chemical structures of the two comonomers on these two latter properties of the copolymers is discussed.     

Synthesis of Cyclic Polyesters of Poly(Oxybutylene Oxymaleoyl)

In the present work cyclic oligomers of poly(oxybutylene oxymaleoyl) were prepared successfully and cleanly from the polycondensation of the tetrahydrofuran with maleïc anhydride using the Maghnite-H⁺ (Mag-H) as catalyst. Maghnite is a montmorillonite sheet silicate clay exchanged with protons to produce Maghnite-H⁺ (M. Belbachir, U.S. Patent 066969.0101–2001). The effects of reaction temperature, amount of Maghnite-H⁺ and reaction time on the yield and the molecular weight are investigated. The results indicate that the polymerization yield increases with increasing the proportion of catalyst.     

Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts

Unsaturated copolyesters are of great interest in polymer science due to their broad potential applications and sustainability. Copolyesters were synthesized from the ring-opening metathesis copolymerization of ω-6-hexadecenlactone (HDL) and norbornene (NB) using ruthenium-alkylidene [Ru(Cl₂)(=CHPh)(1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)(PCy₃)] (Ru1), [Ru(Cl)₂(=CHPh)(PCy₃)₂] (Ru2), and ruthenium-vinylidene [RuCl₂(=C=CH(p-C₆H₄CF₃))(PCy₃)₂] (Ru3) catalysts, respectively, yielding HDL-NB copolymers with different ratios of the monomer HDL in the feed. The activity of N-heterocyclic-carbene (NHC) (Ru1) and phosphine (Ru2 and Ru3) ligands containing ruthenium-carbene catalysts were evaluated in the synthesis of copolymer HDL-NB. The catalysts Ru1 with an NHC ligand showed superior activity and stability over catalysts Ru2 and Ru3 bearing PCy₃ ligands. The incorporation of the monomers in the copolymers determined by ¹H-NMR spectroscopy was similar to that of the HDL-NB values in the feed. Experiments, at distinct monomer molar ratios, were carried out using the catalysts Ru1–Ru3 to determine the copolymerization reactivity constants by applying the Mayo–Lewis and Fineman–Ross methods. The copolymer distribution under equilibrium conditions was studied by the ¹³C NMR spectra, indicating that the copolymer HDL-NB is a gradient copolymer. The main factor determining the decrease in melting temperature is the inclusion of norbornene units, indicating that the PNB units permeate trough the HDL chains. The copolymers with different molar ratios [HDL]/[NB] have good thermal stability up to 411 °C in comparison with the homopolymer PHDL (384 °C). Further, the stress–strain measurements in tension for these copolymers depicted the appreciable increment in stress values as the NB content increases.     

Investigation of styrene/1‐hexene copolymerization by homogeneous and heterogeneous bisindenyl ethane zirconium dichloride catalyst system

Homogeneous copolymerization of styrene and 1‐hexene was carried out in toluene at room temperature using bisindenyl ethane zirconium dichloride/methylaluminoxane (MAO). The supported catalyst was prepared with immobilization of Et(Ind)₂ZrCl₂/MAO on silica (calcinated at 500°C) with premixed method. Heterogeneous copolymerization of styrene/1‐hexene with different mole ratios was carried out in the presence of supported catalyst system. The copolymers obtained from homogeneous and heterogeneous catalyst system were characterized by ¹H NMR and ¹³C NMR. Composition of the resulting copolymers was determined by ¹H NMR data. Analysis of ¹³C NMR spectra of obtained copolymers by homogeneous and heterogeneous catalyst systems present isotactic olefin‐enriched copolymers. Molecular weight and thermal behavior of resulting copolymers was investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4008–4014, 2007     

Synthesis and characterization of controlled molecular weight disulfonated poly(arylene ether sulfone) copolymers and their applications to proton exchange membranes

tert-Butylphenyl terminated disulfonated poly(arylene ether sulfone) copolymers with controlled molecular weights (M_n), 20-50 kg mol⁻¹, were successfully prepared by direct copolymerization of the two activated halides, biphenol and the endcapper, 4-tert-butylphenol. The high molecular weight copolymer (molecular weight over 80 kg mol⁻¹) was also synthesized with 1:1 stoichiometry without an endcapping reagent. The chemical compositions and the molecular weights of the endcapped copolymers were characterized by their ¹H NMR spectra utilizing the 18 unique protons at the chain ends. Modified intrinsic viscosity measurements in 0.05 M LiBr/NMP solution further correlated well with NMR results. Combining the endcapping chemistry with proton NMR end group analysis and intrinsic viscosity measurements, one can demonstrate a powerful tool for characterizing molecular weight of sulfonated poly(arylene ether sulfone) random copolymers. This enables one to further investigate the influence of molecular weight on several critical parameters important for proton exchange membranes, including water uptake, in-plane protonic conductivity and selected mechanical properties. These are briefly discussed herein and will be more fully described in subsequent publications.     

Self‐assembled micelles prepared from poly(ɛ‐caprolactone)–poly(ethylene glycol) and poly(ɛ‐caprolactone/glycolide)–poly(ethylene glycol) block copolymers for sustained drug delivery

A series of poly(?‐caprolactone)–poly(ethylene glycol) (PCL‐PEG) and poly(?‐caprolactone/glycolide)–poly(ethylene glycol) [P(CL/GA)‐PEG] diblock copolymers were prepared by ring‐opening polymerization of ?‐caprolactone or a mixture of ?‐caprolactone and glycolide using monomethoxy PEG (mPEG) as macroinitiator and Sn(Oct)₂ as catalyst. The resulting copolymers were characterized using ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Copolymer micelles were prepared using the nanoprecipitation method. The morphology of the micelles was spherical or worm‐like as revealed by transmission electron microscopy, depending on the copolymer composition and the length of the hydrophobic block. Introduction of the glycolide component, even in small amounts (CL/GA = 10), disrupted the chain structure and led to the formation of spherical micelles. Interestingly, the micelle size decreased with the encapsulation of paclitaxel. Micelles prepared from mPEG5000‐derived copolymers exhibited better drug loading properties and slower drug release than those from mPEG2000‐derived copolymers. Drug release was faster for copolymers with shorter PCL blocks than for those with longer PCL chains. The introduction of glycolide moieties enhanced drug release, but the overall release rate did not exceed 10% in 30 days. In contrast, drug release was enhanced in acidic media. Therefore, these bioresorbable micelles and especially P(CL/GA)‐PEG micelles with excellent stability, high drug loading content, and prolonged drug release could be promising for applications as drug carriers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45732.     

Synthesis and characterization of biodegradable copolymers based on 6-aminocaproic acid and α-L-alanine

Random copolymers based on 6-aminocaproic acid and α-L-alanine were prepared by melt phase polycondensation method and characterized by FTIR, ¹H NMR, DSC and WAXD. The density, water absorptivity and enzymatic degradation of copolymers were measured. The results show that with increasing of alanine content in comonomers, the density, water absorptivity and rate of enzymatic degradation of copolymers increase, but the intrinsic viscosity and the degree of crystallization decrease. When the molar percentage of alanine increases to 40% in comonomers, copolymer is amorphous.     

Synthesis,characterization of star-shaped copolymers of <Emphasis Type="SmallCaps">l</Emphasis>-lactide and epoxidized soybean oil

Biodegradable star-shaped PLLA–ESO copolymers were synthesized by the bulk copolymerization of l-lactide (l-LA) and epoxidized soybean oil (ESO) with stannous octanoate as the catalyst. Effects of molar ratios of monomer to catalyst, and various amounts of ESO on copolymerization were studied. The resulting copolymers were characterized by FTIR, ¹H NMR, GPC, etc., which confirmed the successful synthesis of star-shaped copolymers of l-LA and ESO. The thermal and mechanical properties of samples were also investigated by means of DSC, TGA and tensile testing. The results showed that the PLLA–ESO copolymers possed lower glass transition temperature, melting point, crystallinity, and maximum decomposition temperature than those of neat polylactide. Tensile testing demonstrated that PLLA–ESO copolymer had better ductility than linear PLLA. It was also found that the amount of catalyst almost had no influence on the weight average molecular weight of PLLA–ESO copolymers, but which could be controlled by variation of molar ratios of l-LA to ESO.     

Synthesis and properties of unsaturated polyoxyethylene and its graft copolymers with styrene

The unsaturated polyoxyethylene (PEO) was synthesized by copolymerization of ethylene oxide with allyl glycidyl ether in toluene using bimetallic-oxo-alkoxide as a catalyst. The effects of polymerization conditions on conversion and intrinsic viscosity of the copolymer were studied. The unsaturated copolymer was characterized with infrared spectra, ¹H NMR, and wide-angle X-ray diffraction. The relationship between crystallinity of the copolymers and conductivity of their LiClO₄ complexes were investigated. The copolymer with ∼ 65 wt % PEO content exhibits a room temperature conductivity of 1 × 10⁻⁴ S cm⁻¹ at a molar ratio of EO/Li = 20. The unsaturated PEO was graft-copolymerized with styrene using 2,2′-azobis(isobutyronitrile) as initiator in toluene, with grafting efficiency ∼ 50%. The purified graft copolymer was characterized with infrared spectra, ¹H NMR, and wide-angle X-ray diffraction, and was shown to have good emulsifying properties and a phase-transfer catalytic property. LiClO₄ complex of the graft copolymer with 70 wt % PEO content exhibits a room temperature conductivity approaching 1 × 10⁻⁴ S cm⁻¹ at molar ratio of EO/Li = 20/1. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2417–2425, 1998     

Synthesis and characterization of poly(oxyethylene)–poly(caprolactone) multiblock copolymers

Novel poly(oxyethylene)/poly(caprolactone) POE/PCL copolymers were synthesized by step growth polymerization of poly(ε-caprolactone) diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. The reaction was performed at room temperature and yielded multiblock copolymers with predetermined POE and PCL block lengths. The resulting copolymers were characterized by various analytical techniques including SEC, IR, ¹H NMR, DSC and X-ray diffractometry. Data showed that the properties of these polymers can be modulated by adjusting the chain lengths of the macromonomers. In particular, one or two crystalline structures can exist within the copolymers of various crystallinities. © 1998 SCI.     

Concentration effect of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide on viscoelastic properties of hydrosoluble thermo-thickening copolymers

In this work, we described the preparation of hydrosolubles thermosensitive copolymers obtained via free radical polymerization in aqueous media. The reactions were carried out under different molar ratio of acrylamide and N-isopropylacrylamide (NIPAM) and are considered [80]/[20], [60]/[40], [50]/[50], [40]/[60] and [20]/[80], respectively. The initial concentration of monomer mixture was kept at 3% (weight) based on the water volume. The polymerizations were performed at 70 °C under mechanical agitation during 7 h and the molar ratio between monomer and initiator (4,4′-azobis cyano pentanoic acid) was kept at 0.07%. The copolymers were characterized and results demonstrated that the monomer concentrations were closed to previously feed to the reaction. The turbidity point rises according to the quantity of poly(acrylamide), PAM, incorporated into the copolymers (composition value). Also, it was observed that the molecular weight of each copolymer decreases when the amount of NIPAM increases. On the other hand, the viscosity of all copolymers growth compared to the increase in the temperature from 25 to 70 °C is observed. Notwithstanding, in the case of copolymer with highest NIPAM concentration (CP5), the viscosity decreases in the temperature range from 60 to 70 °C.