Cationic curing of diglycidyl ether of bisphenol A and 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane and degradation of the thermosets obtained

Ytterbium and lanthanum triflates were used as cationic initiators to cure mixtures of diglycidyl ether of bisphenol A and 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane in several proportions. The evolution of the epoxy and lactone during curing and the linear ester groups in the final materials were evaluated with Fourier transform infrared in the attenuated total reflection mode. The shrinkage after curing and the thermal degradability of the materials with variations in the comonomer ratios and initiator used were evaluated and related to the chemical structure of the final network. The expandable character of 2,2,5,5‐tetramethyl‐4,6‐dioxo‐1,3‐dioxane was confirmed. The obtained materials were more degradable than conventional epoxy resins because of the tertiary ester groups incorporated into the network by copolymerization. The kinetic parameters of the curing and degradation processes were calculated with differential scanning calorimetry and thermogravimetric analysis, respectively, with isoconversional procedures applied in both cases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymerization of lactides and lactones. II. Ring‐opening polymerization of ε‐caprolactone and DL‐lactide by organoacid rare earth compounds

Ring‐opening polymerization of lactone and lactide have been initiated with rare earth organoacid compounds, such as lanthanum acetate in bulk. The polymerization mechanism is in agreement with the “nonionic–coordination–insertion” mechanism, which involves the selective cleavage of the acyl–oxygen bond of the monomer. These organoacid rare earth initiators can give high yield of medium to high molecular weight products. An interesting aspect of this investigation is the good agreement between the performance of the initiator and the solubility of the initiator in the monomer. However, the relatively slow initiation step makes it difficult to control the molecular weight and results in a broad molecular weight distributions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1941–1948, 1999     

Maghnite‐H+ as a cationic catalyst in the synthesis of poly(1,3‐dioxolane) and α,ω‐methacryloyloxy‐poly(1,3‐dioxolane)

The polymerization of 1,3‐dioxolane catalyzed by Maghnite‐H^+; (Mag‐H⁺), a montmorillonite sheet silicate clay exchanged with protons, was investigated. The cationic ring‐opening polymerization of 1,3‐dioxolane was initiated by Mag‐H⁺ at different temperatures (20, 30, 50, and 70°C) in bulk and in a solvent (dichloromethane). The effects of the amount of Mag‐H⁺ and the temperature were studied. The polymerization rate and the average molecular weights increased with an increase in the temperature and the proportion of the catalyst. These results indicated the cationic nature of the polymerization and suggested that the polymerization was initiated by proton addition to the monomer from Mag‐H⁺. Moreover, we used a simple method, in one step in bulk and in solution at room temperature (20°C), to prepare a telechelic bismacromonomer: α,ω‐bisunsaturated poly(1,3‐dioxolane). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 78–82, 2006     

Cationic polymerization of isoprene using zinc halides as co‐initiators: towards well‐defined oligo(isoprene)s under mild conditions

The activity of ZnX₂‐based initiating systems (X = Cl, Br, I) in the cationic polymerization of isoprene was studied. The highest activity was achieved when co‐initiator (ZnX₂) was solubilized in a minimal amount of strongly coordinating solvent such as diethyl ether or acetone and when trichloroacetic acid was used as an initiator. It is shown that the polymerization rate increased in the series ZnI₂ < ZnCl₂ < ZnBr₂. An increase of initiator concentration and temperature also led to an increase of the polymerization rate. The obtained polyisoprenes did not contain high‐molecular‐weight and insoluble fractions and were characterized by low number‐average molecular weight and relatively narrow molecular weight distribution. Unsaturation of polyisoprene decreased with an increase of monomer conversion and reaction temperature. The unsaturated part of the polyisoprene chain possessed predominantly 1,4‐trans microstructure with regular and inverse addition, whereas the 1,2‐ and 3,4‐isomers were present as minor components. It is shown that the synthesized low‐molecular‐weight polyisoprenes are effective plasticizers for rubber compounds in the manufacture of tyres. © 2012 Society of Chemical Industry     

Random copolymerization of 2,2‐dimethyltri methylene carbonate and ε‐caprolactone using a rare‐earth tris(4‐tert‐butylphenolate)s as a single‐component initiator

Highly random copolymers of 2,2‐dimethyltrimethylene carbonate (DTC) and ε‐caprolactone (CL) were synthesized by single component rare‐earth tris(4‐tert‐butylphenolate)s [Ln(OTBP)₃] for the first time. The influences of reaction conditions on the copolymerization initiated by La(OTBP)₃ have been examined in detail. The monomer reactivity ratios of DTC and CL determined by the Fineman–Ross method are 4.0 for r_DTC and 0.27 for r_CL. The microstructure of the copolymer was determined by the analyses of the diads DTC–DTC, DTC–CL, CL–DTC and CL–CL of the ¹H NMR spectra. The high degree of randomness of the chain structure was further confirmed by the ¹³C NMR spectra and differential scanning calorimetry. The thermal properties of the copolymers as a function of composition are reported. The mechanism investigated by ¹H NMR data indicates that the rare‐earth tris(4‐tert‐butylphenolate)s initiate the ring‐opening copolymerization of DTC and CL with acyl‐oxygen bond cleavages of the monomers. Copyright © 2004 Society of Chemical Industry     

Investigation of the interaction of CO2 with poly (L‐lactide), poly(DL‐lactide) and poly(ε‐caprolactone) using FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was used to reveal intermolecular interactions between carbon dioxide (CO₂) and the carbonyl groups of poly(L ‐lactide) (PLLA), poly(D,L ‐lactide) (PDLLA), and poly(ε‐caprolactone) (PCL). After exposing polymer films to high pressure CO₂, the wave number of the absorption maxima of the polymer carbonyl groups shifted to higher values. Also, due to the interaction between CO₂ and the carbonyl groups of the polymers, a new broad peak in the bending mode region of CO₂ appeared. To distinguish between polymer‐associated and nonassociated CO₂, and to quantify these contributions, the bending mode peaks were deconvoluted. From these contributions, it was found that in the case of PCL more CO₂ is interacting with the polymer carbonyl groups than in the case of PDLLA and PLLA. Under our experimental conditions, 40°C and pressures up to 8 MPa, a significant depression of the PCL melting temperature was observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymerization of styrene using bis(β‐ketoamino)nickel(II)/methylaluminoxane catalytic systems

Styrene (St) was polymerized in toluene solution by using bis(β‐ketoamino)nickel(II) complex as the catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. The polymerization conditions, such as Al : Ni ratio, monomer concentration, reaction temperature, and polymerization time, were studied in detail. Both of the bis(β‐ketoamino)nickel(II)/MAO catalytic systems exhibited higher activity for polymerization of styrene, and polymerization gave moderate molecular weight of polystyrene with relatively narrow molecular weight distribution (M_w/M_n < 1.6). The obtained polymer was confirmed to be atactic polystyrene by analyzing the stereo‐triad distributions mm, mr, and rr of aromatic carbon C¹ in NMR spectrum of the polymer. The mechanism of the polymerization was also discussed and a metal–carbon coordination mechanism was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Polymerization of norbornene using bis(β‐ketoamino)nickel(II)/MAO catalytic systems

The polymerizations of norbornene were investigated using a series of bis(β‐ketoamino)nickel(II) complexes( 1–6 ) in combination with methylaluminoxane (MAO) in toluene solution. The effects of catalyst structure, Al/Ni molar ratio, reaction temperature, and reaction time on catalytic activity and molecular weight of the polynorbornene were examined in detail. The electronic effect of the substituent around the imino group in the ligand is stronger than the steric bulk one on the polymerization activities, and the activities are in the order of 1 > 2 > 4 > 5 > 6 > 3 . The obtained polynorbornenes were characterized by means of ¹H‐NMR, ¹³C‐NMR, FTIR, TG, and WAXD techniques. The analyses results of polymers' structures and properties indicate that the polymerization reaction of norbornene runs in vinyl‐addition polymerization mode. The obtained polynorbornene was confirmed to be vinyl‐type and atactic polymers and showed good thermostability (T_dec > 458°C) and were noncrystalline but had short‐range order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4172–4180, 2006     

Synthesis of vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) catalyzed by rare earth solid super acid SO42‐/TiO2/Ln3+

Rare earth solid super acids SO₄^2?/TiO₂/Ln³⁺ have been successfully developed to synthesize vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) end‐capped with 1,1,3,3‐tetramethyl‐1,3‐divinyldisiloxane. The features of ring opening polymerization reactions have been investigated in detail. The preferable conditions for the ring opening polymerization of D4 are as follows: [Nd³⁺] = 0.07 mol L^?1 and [SO₄^2?] = 1.85 mol L^?1 in the immersing solution; the amount of SO₄^2?/TiO₂/Nd³⁺ calcined at 500 °C was 5 wt% of the amount of D4; polymerization at 80 °C for 1 h. The average molecular weights of the products obtained using various rare earth catalysts were in order Nd > La > Sm > Gd, which shows that the light rare earths were more favorable for higher molecular weight products than the heavy ones. According to the polymerization features, a cationic equilibrium reaction mechanism is proposed. © 2013 Society of Chemical Industry     

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

The ring‐opening polymerization of ε‐caprolactone initiated with a divalent samarium bis(phosphido) complex [Sm(PPh₂)₂] is reported. The polymerization proceeded under mild reaction conditions and resulted in polyesters with number‐average molecular weights of 8.2 × 10³ to 12.5 × 10³. The yield and molecular weight of poly(ε‐caprolactone)s were dependent on the experimental parameters, such as the monomer/initiator molar ratio, the monomer concentration, the reaction temperature, and the polymerization time. The obtained polymers were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and differential scanning calorimetry. On the basis of an end‐group analysis of low‐molecular‐weight polymers by NMR spectroscopy, a coordination–insertion mechanism is proposed for the polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1558–1564, 2005     

Tetrahydrosalen‐stabilized,chloride‐containing rare‐earth complexes: Facile initiator precursors for the preparation of hydroxytelechelic poly(ε‐caprolactone)s

End‐capped poly(ε‐caprolactone)s (PCLs) have been prepared elsewhere by various initiators. However, hydroxytelechelic PCLs have been reported less frequently, although there are two hydroxyl end groups in one polymer chain, which allows diversified functionalization. Two tetrahydrosalen‐backboned chlorides containing rare‐earth complexes, YbLCl(DME)₂ and ErLCl(DME) {where L is 6,6′‐[ethane‐1,2‐diylbis(methylazanediyl)]bis (methylene)bis(2,4‐di‐tert‐butylphenol) and DME is dimethoxyethane}, were first synthesized in this study, and they were used as initiator precursors for a ring‐opening polymerization in the presence of NaBH₄ to afford hydroxytelechelic PCLs. The polymerization under different conditions was investigated, and a possible mechanism is proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

α‐Bis and α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polymers by atom transfer radical polymerization using 1,1‐bis[(4‐dimethylamino)phenyl]ethylene as tertiary diamine initiator precursor and functionalizing agent

The quantitative syntheses of α‐bis and α,ω‐tetrakis tertiary diamine functionalized polymers by atom transfer radical polymerization (ATRP) methods are described. A tertiary diamine functionalized 1,1‐diphenylethylene derivative, 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1), was evaluated as a unimolecular tertiary diamine functionalized initiator precursor as well as a functionalizing agent in ATRP reactions. The ATRP of styrene, initiated by a new tertiary diamine functionalized initiator adduct (2), affords the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3). The tertiary diamine functionalized initiator adduct (2) was prepared in situ by the reaction of (1‐bromoethyl)benzene with 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) in the presence of a copper (I) bromide/2,2′‐bipyridyl catalyst system. The ATRP of styrene proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene derivative (3) with predictable number‐average molecular weight (M_n) and narrow molecular weight distribution (M_w/M_n) in a high initiator efficiency reaction. The polymerization process was monitored by gas chromatography analysis. Quantitative yields of α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polystyrene (4) were obtained by a new post ATRP chain end modification reaction of α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3) with excess 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1). The tertiary diamine functionalized initiator precursor 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) and the different tertiary amine functionalized polymers were characterized by chromatography, spectroscopy and non‐aqueous titration measurements. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of novel lipid functionalized poly(ε‐caprolactone)s

A series of novel lipid functionalized poly(ε‐caprolactone)s (PCLs) were synthesized through ROP of ε‐caprolactone in the presence of threo‐9,10‐dihydroxyoctadecanoic acid, synthesized from oleic acid. PCLs with different molecular weights were obtained by controlling the molar ratio of the initiator to the monomer. DSC and XRD analysis indicate that the crystallinity of PCLs decreased when compared to unfunctionalized PCL. The enzymatic degradation study shows that for samples with lower lipid derivatives content, a higher enzymatic degradation rate was observed because the lipase enzymes attack the ester bonds of the polymer; increased lipid content therefore inhibits the action of the lipase enzymes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Copolymerization of ethylene/α‐olefins using bis(2‐phenylindenyl)zirconium dichloride metallocene catalyst: structural study of comonomer distribution

Catalysts have a major role in the polymerization of olefins and exert their influence in three ways: (1) polymerization behaviour, including polymerization activity and kinetics; (2) polymer particle morphology, including bulk density, particle size, particle size distribution and particle shape; and (3) polymer microstructure, including molecular weight regulation, chemical composition distribution and short‐ and long‐chain branching. By tailoring the catalyst structure, such as the creation of a bridge or introducing a substituent on the ligand, metallocene catalysts can play a major role in the achievement of desirable properties. Kinetic profiles of the metallocene catalyst used in this study showed decay‐type behaviour for copolymerization of ethylene/α‐olefins. It was observed that increasing the comonomer ratio in the feedstock affected physical properties such as reducing the melting temperature, crystallinity, density and molecular weight of the copolymers. It was also observed that the heterogeneity of the chemical composition distribution and the physical properties were enhanced as the comonomer molecular weight was increased. In particular, 2‐phenyl substitution on the indenyl ring reduced somewhat the melting point of the copolymers. In addition, the copolymer produced using bis(2‐phenylindenyl)zirconium dichloride (bis(2‐PhInd)ZrCl₂) catalyst exhibited a narrower distribution of lamellae (0.3–0.9 nm) than the polymer produced using bisindenylzirconium dichloride catalyst (0.5–3.6 nm). The results obtained indicate that the bis(2‐PhInd)ZrCl₂ catalyst showed a good comonomer incorporation ability. The heterogeneity of the chemical composition distribution and the physical properties were influenced by the type of comonomer and type of substituent in the catalyst. Copyright © 2010 Society of Chemical Industry     

Functionalization of multi‐walled carbon nanotubes with poly(ε‐caprolactone) using click chemistry

Multi‐walled carbon nanotubes (MWNTs) were covalently functionalized with poly(ε‐caprolactone) (PCL) using click chemistry. First, chlorine moiety‐containing PCL was synthesized by the copolymerization of α‐chloro‐ε‐caprolactone with ε‐caprolactone monomer using ring opening polymerization, and further converted to azide moiety‐containing PCL. The alkyne‐functionalized MWNTs were prepared with the treatment of p‐amino propargyl ether using a solvent free diazotization procedure. The covalent functionalization of alkyne‐derived MWNTs with azide moiety‐containing PCL was accomplished using Cu(I)‐catalyzed [3+2] Huisgen dipolar cycloaddition click chemistry. The PCL‐functionalization of MWNTs was confirmed by the measurements of Fourier transform infra‐red, NMR, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Ring‐opening polymerization of ε‐caprolactone by a new yttrium complex: Y[2,2′‐ethylidene‐bis(4,6‐di‐tert‐butylphenoxy)]2(ethylene glycol dimethyl ether)Na(ethylene glycol dimethyl ether)3

The main aims of the work reported here were to synthesize and characterize a new 2,2′‐ethylidene‐bis(4,6‐di‐tert‐butylphenol) (EDBPH₂)‐based bimetal yttrium complex, Y(EDBP)₂(DME)Na(DME)₃ (1c; where DME is ethylene glycol dimethyl ether), which was employed as an efficient initiator for the ring‐opening polymerization of ε‐caprolactone (ε‐CL). From single‐crystal X‐ray diffraction, the solid structure of this new bimetal initiator was well established. Experimental results show that 1c initiates the ring‐opening polymerization of ε‐CL to afford poly(ε‐CL) with a narrow molecular weight distribution (M_w/M_n = 1.09–1.36, 65 °C). Based on an in situ NMR study, a plausible coordination–insertion mechanism is then proposed. The bimetal complex 1c can be used as an initiator for the ring‐opening polymerization of ε‐CL with some living characteristics. A study of the mechanism reveals that DME displacement in 1c by ε‐CL is involved in the initiation process and the propagation may proceed through three pathways by Na? O insertion or Y? O insertion. Copyright © 2009 Society of Chemical Industry     

Infrared study on in situ polymerization of zinc dimethacrylate in poly(α‐octylene‐co‐ethylene) elastomer

An infrared spectroscopic method was used to follow the course of in situ polymerization of zinc dimethacrylate (ZDMA) in poly(α‐octylene‐co‐ethylene) elastomer (POE). The integral intensity of the 831 cm^?1 band, ie the out‐of‐plane deformation mode of ?CH, was used to determine the residual amount of ZDMA in composites cured at 165°C for different times, through which the course of in situ polymerization of ZDMA in POE was traced and the dynamic curve determined. The curing course of the ZDMA/POE/peroxide system at 165°C was examined with a rheometer and compared with the course of in situ polymerization. The results surprisingly show that the in situ polymerization of ZDMA is almost complete at the beginning stage of curing, and that substantial crosslinking starts subsequently. Scanning electron microscopy and transmission electron microscopy observations on morphologies of ZDMA/POE composites cured at 165°C for different times were carried out and confirmed the results of infrared experiments. Combining all the investigations, it was deduced that a competition exists between in situ polymerization and crosslinking in the composites. Covalent crosslinking rather than ionic bond crosslinks are the major types of crosslinks structures in ZDMA/POE composites, and its total density is lower than that of carbon‐ black‐reinforced POE. Copyright © 2004 Society of Chemical Industry     

Poly(2‐oxazoline)s: A comprehensive overview of polymer structures and their physical properties

Poly(2‐oxazoline)s (PAOx) are of increasing importance for a wide range of applications, mostly in the biomedical field. This review describes the synthesis of 2‐oxazoline monomers and their cationic ring‐opening polymerization, and gives a comprehensive overview of all reported PAOx homopolymers. In the second part of the review, the polymer properties of these PAOx homopolymers with varying side‐chain structures are discussed. Altogether, this review intends to serve as an encyclopedia for poly(2‐oxazoline)s enabling the straightforward selection of a polymer structure with the desired properties for a certain application. © 2017 Society of Chemical Industry     

Synthesis,spectral, and thermal characterization of photosensitive poly(ether–ester)s containing α,β‐unsaturated ketone moieties in the main chain derived from 2,6‐bis[4‐(3‐hydroxypropyloxy)‐3‐methoxybenzylidene]cyclohexanone

A series of photosensitive poly(ether–ester)s containing α,β‐unsaturated ketone moieties in the main chain were synthesized from 2,6‐bis[4‐(3‐hydroxypropyloxy)‐3‐methoxybenzylidene]cyclohexanone (BHPMBCH) and aliphatic and aromatic diacid chlorides. The diol precursor, BHPMBCH, was synthesized from 2,6‐bis(4‐hydroxy‐3‐methoxybenzylidene)cyclohexanone and 3‐bromo‐1‐propanol. The solubility of the polymers was tested in various solvents. The intrinsic viscosity of the synthesized polymers, determined by an Oswald viscometer, was found to be 0.06–0.80 g/dL. The molecular structures of the monomer and polymers were confirmed by Fourier transform infrared, ultraviolet–visible, ¹H‐NMR, and ¹³C‐NMR spectral analyses. The thermal properties were studied with thermogravimetric analysis and differential scanning calorimetry. The thermogravimetric analysis data revealed that the polymers were stable up to 220°C and started degrading thereafter. The thermal stability initially increased with increasing spacer length and then decreased due to negative effects of the spacer. The self‐extinguishing properties of the synthesized polymers were studied by the determination of the limiting oxygen index values with Van Krevelen's equation. In addition, the photocrosslinking properties of the polymer chain were studied with UV spectroscopy, and we observed that the rate of photocrosslinking increased significantly with increasing methylene carbon chain length of the acid spacer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011