Cure characterization of the ring‐opening metathesis polymerization of linseed oil‐based thermosetting resins

BACKGROUND: Bio‐based polymers from vegetable oils are excellent alternatives to petroleum‐based resins for both environmental and economic reasons. A detailed understanding of the cure behavior of bio‐based polymers is essential to optimize cure schedules and the final properties of the polymers. In this work, the cure of newly developed linseed oil‐based thermosetting resins, synthesized using Grubbs' first‐generation catalyst and a bis‐norbornadiene cross‐linking agent by ring‐opening metathesis polymerization, is characterized using differential scanning calorimetry (DSC) and parallel plate oscillatory rheometry. RESULTS: Experimental results reveal that the rate of cure increases and the gel time decreases with increasing cross‐linker loading; however, the activation energy of the cure does not vary systematically with cross‐linker loading. Phenomenological reaction models are used to describe the dynamic DSC measurements and to determine the kinetic parameters which facilitate cure predictions under isothermal conditions. CONCLUSION: This work demonstrates that the cure kinetics of a linseed oil‐based thermosetting resin can be controlled by varying the cross‐linker loading. Furthermore, the kinetic parameters and cure rates at any cross‐linker loading for this system can be described by a simple autocatalytic reaction model which facilitates development of cure schedules. Copyright © 2009 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     

Potential synthesis of poly(1,2‐dichloroethylene) via a ring‐opening metathesis polymerization

The preparation of poly(1,2‐dichloroethylene), an unknown material that has been expected to be a superb engineering thermoplastic, was explored. The ring‐opening metathesis polymerization of cis‐3,4‐dichlorocyclobutene quantitatively yielded a white linear polymer with ? CHClCHClCH?CH? repeating units. However, its subsequent addition chlorination could not be made to occur to a detectable level. Steric hindrance and/or electronic deactivation due to the inductive effect of Cl apparently made the chlorination impossible. Furthermore, thermal degradation studies of a series of model compounds indicated that polymers containing (CHCl)_n (n ≥ 3) structures would have low thermal stabilities. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

UV‐ and thermally triggered ring‐opening metathesis polymerization for the spatially resolved functionalization of polymeric monolithic devices

Porous polymeric monolithic supports were prepared via electron beam‐triggered free radical polymerization using a mixture of ethyl methacrylate and trimethylolpropane triacrylate in 2‐propanol, 1‐dodecanol and toluene. Bicyclo[2.2.1]hept‐5‐en‐2‐ylmethyl acrylate (1) was grafted onto these monolithic supports in a spatially resolved way with the aid of masks using both electron beam‐ (EB) and UV‐triggered free radical polymerization. The thus immobilized norborn‐2‐ene‐containing graft polymers were further treated with the 2^nd‐generation Grubbs initiator, i.e., RuCl₂(PCy₃)(IMesH₂)(CHPh) (4) (IMesH₂ = 1,3‐dimesitylimidazolin‐2‐ylidene), and then reacted with bicyclo[2.2.1]hept‐5‐en‐2‐ylmethyl pyrene‐1‐carboxylate (2). Alternatively, monoliths completely grafted with poly‐ 1 were surface grafted with 2 in a spatially resolved way in the presence of a latent, UV‐triggerable precatalyst, i.e., [Ru(IMesH₂)(CF₃COO)(t‐BuCN)₄⁺ CF₃COO^?] (5). Finally, to demonstrate the utility of this chemistry, a 2^nd‐generation Grubbs initiator‐based approach was used to prepare a trypsin‐functionalized monolith‐containing chip device that allowed for the online digestion of N‐α‐benzoyl‐L ‐argininethylester hydrochloride. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tung oil‐based thermosetting polymers for self‐healing applications

Several bio‐renewable thermosetting polymers were successfully prepared from tung oil through cationic polymerization for the use as the healing agent in self‐healing microencapsulated applications. The tung oil triglyceride was blended with its methyl ester, which was produced by saponification followed by esterification. The changes in storage modulus, loss modulus, and glass transition temperature as functions of the methyl ester content were measured using dynamic mechanical analysis. In addition, the fraction of cross‐linked material in the polymer was calculated by Soxhlet extraction, while proton nuclear magnetic resonance, Fourier transform infrared spectroscopy and TEM were used to investigate the structure of the copolymer networks. The thermal stability of the thermosets as a function of their methyl ester blend contents was determined by thermogravimetric analysis. Finally, the adhesive properties of the thermosets were studied using compressive lap shear and the fracture surfaces were analyzed using SEM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40406.     

Novel thermosets obtained by the ring‐opening metathesis polymerization of a functionalized vegetable oil and dicyclopentadiene

New polymeric thermosetting resins prepared by the ring‐opening metathesis polymerization (ROMP) of a commercially available vegetable oil derivative, Dilulin, and dicyclopentadiene (DCPD) have been prepared and characterized. A thorough characterization of the modified oil itself has been carried out to elucidate its structure. Grubbs' second‐generation catalyst has been used to effect the ROMP of the strained unsaturated norbornene‐like rings in the commercial oil. Dynamic mechanical analysis of the resulting thermosetting resins has revealed that glass‐transition temperatures ranging from 36 to ?29°C can be obtained when the proper ratio of oil to DCPD is employed. Thermogravimetric analysis has revealed that these resins have very similar temperatures of maximum degradation. Extraction analysis has indicated that all the samples had at least a 20% soluble fraction and that the soluble fraction was composed of oligomers, unreacted triglyceride oil, or both. The effect of the soluble fraction as a plasticizer has also been explored. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of poly(cyclooctene) by ring‐opening metathesis polymerization: Characterization and shape memory properties

Cis‐cyclooctene was polymerized via ring‐opening metathesis polymerization using a well‐defined ruthenium catalyst (Grubbs' type) under varying reaction conditions. Control over molecular weight was achieved by the inclusion of a chain transfer agent and its influence on the behavior of the obtained polymers was evaluated. The resulting polymers were characterized by means of differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. Taking into account their thermal behavior, samples of appropriate molecular weight were subjected to a suitable treatment by chemical crosslinking to obtain a material showing thermally induced shape memory effect. The material recovers its original shape after several cycles of deformation into different shapes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhancement of mechanical and tribological properties in ring‐opening metathesis polymerization functionalized molybdenum disulfide/polydicyclopentadiene nanocomposites

This study focuses on the possibility of improving performance properties of polydicyclopentadiene (PDCPD) nanocomposites for engineering applications using nanoparticles. In this article, molybdenum disulfide/polydicyclopentadiene (MoS₂/PDCPD) nanocomposites have been prepared by in situ ring‐opening metathesis polymerization using reaction injecting molding (RIM) process. To enhance the interfacial adhesion between the fillers and PDCPD matrix, the surface modified MoS₂ nanoparticles hybridized with dialkyldithiophosphate (PyDDP) were successfully prepared by in situ surface grafting method. The effect of low MoS₂ loadings (<3 wt %) on the mechanical and tribological behaviors of PDCPD was evaluated. The results indicated that the friction coefficient of the MoS₂/PDCPD nanocomposites was obviously decreased and the wear resistance of nanocomposites was greatly improved by the addition of PyDDP‐hybridized MoS₂ nanoparticles; meanwhile, the mechanical properties were also enhanced. The MoS₂/PDCPD nanocomposites filled with 1 wt % PyDDP‐hybridized MoS₂ exhibited the best mechanical and anti‐wear properties. The friction coefficient was shown to decrease by more than 40% compared to pure PDCPD by incorporating just 1 wt % hybridized MoS₂ nanoparticles, and modest increase in modulus and strength was also observed. The reinforcing and wear‐resistant mechanisms of MoS₂/PDCPD nanocomposites were investigated and discussed by scanning electron microscopy. The well interfacial compatibility between the particle/matrix interfaces played an important role for the improved mechanical and tribological properties of MoS₂/PDCPD nanocomposites in very low MoS₂ loadings. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thiol‐Michael coupling and ring‐opening metathesis polymerization: facile access to functional exo‐7‐oxanorbornene dendron macromonomers

This paper describes the synthesis of the 2‐ and 4‐functional acrylic exo‐7‐oxanorbornene species 2‐((2‐((3aR,7aS)‐1,3‐dioxo‐1,3,3a,4,7,7a‐hexahydro‐2H‐4,7‐epoxyisoindol‐2‐yl)ethoxy) carbonyl)‐2‐methylpropane‐1,3‐diyl diacrylate and (((2‐((2‐((3aR,7aS)‐1,3‐dioxo‐1,3,3a,4,7,7a‐hexahydro‐2H‐4,7‐epoxyisoindol‐2‐yl)ethoxy) carbonyl)‐2‐methylpropane‐1,3‐diyl)bis(oxy))bis(carbonyl))bis(2‐methylpropane‐2,1,3‐triyl) tetraacrylate, and their use as common precursors for the preparation of a small library of dendronized thioether adducts via nucleophile‐mediated thiol‐Michael coupling chemistry. We subsequently demonstrate that the dendronized monomers can be (co)polymerized via ring‐opening metathesis polymerization employing Grubbs'‐type Ru‐based initiators to give novel functional dendronized (co)polymers of predictable molecular weights and acceptable dispersities (?_M = _w/ _n). © 2013 Society of Chemical Industry     

Synthesis and ring‐opening polymerization of macrocyclic aromatic sulfide oligomers

A series of macrocyclic(arylene sulfide) oligomers were synthesized by reaction of 4,4′‐oxybis(benzenethiol) with a number of difluoro compounds in dimethylformamide (DMF) in the presence of anhydrous K₂CO₃ under high dilution conditions. The difluoro compound can be 4,4′‐difluorobenzophenone, bis(4‐fluorophenyl)sulfone or 1,3‐bis(4‐fluorobenzoyl)benzene. Detailed structural characterization of these oligomers by matrix‐assisted laser desorption and ionization‐time of flight‐mass spectroscopy (MALDI‐TOF‐MS) demonstrated their cyclic nature. The MALDI‐TOF‐MS technique has proved to be a powerful tool to analyze these cyclics. These cyclic oligomers are amorphous and highly soluble in DMF and N,N′‐dimethyl acetamide. Moreover, these cyclic(arylene sulfide) oligomers readily underwent ring‐opening polymerization in the melt at 285 °C in the presence of 2,2′‐dibenzothiazole disulfide, affording linear, high molecular weigh poly(aromatic sulfide)s. These polymers are insoluble in most common solvents. Copyright © 2004 Society of Chemical Industry     

Silica‐based self‐healing microcapsules for self‐repair in concrete

New self‐healing material for concrete repair has been fabricated through microencapsulation of silica sol via interfacial polymerization of poly(urea‐urethane). Smooth, uniform, and spherical capsules of 60–120 µm sizes were synthesized and optimized by studying the emulsification and polymerization steps of its synthesis. A hydrophile–lyophile balance (HLB) value of 3.0–5.0 and a rotational speed of 500 rpm were necessary to produce a stable emulsion system of silica sol in surfactants. The polymerization speed of 900 rpm and the methylene diisocyanate (MDI) monomer content of 15 wt % were both significant in getting the right size and smoothness of the microcapsules. With this method and cheap healing agents, industrial scale‐up is highly possible. The viscoelastic properties of the microcapsules were examined, and further characterizations were carried out through scanning electron microscopy, energy dispersive X‐ray spectroscopy, and Fourier transform infrared spectroscopy. After healing the microcracks in concrete, the results showed that the significant increase of compressive and bending strengths manifested the self‐healing ability of the microcapsules in concrete. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43090.     

Zinc lactate‐catalyzed ring‐opening polymerization of trimethylene carbonate under microwave irradiation

Microwave‐assisted ring‐opening polymerization (MROP) of trimethylene carbonate (TMC) was carried out with four different types of zinc lactate, as the catalyst. Poly(trimethylene carbonate)s (PTMC) with a number–average molar mass ranging from 2990 to 75,410 g/mol and a TMC conversion ranging from 85.2% to 98.2% were synthesized effectively in 30 min at 120°C under microwave irradiation. The effects of the catalyst type, catalyst concentration, and microwave irradiation time on the MROP of TMC were studied. The MROP of TMC was much faster than that under conventional heating conditions. Thermal analysis suggested that PTMC with higher molar mass exhibited higher glass transition temperature (T_g) and thermal stability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Preparation of polytetrahydrofuran monomethacrylate macromonomers by cationic ring‐opening polymerization of tetrahydrofuran

Polytetrahydrofuran monomethacrylate (MA‐PTHF) macromonomer was prepared by cationic ring‐opening polymerization(CROP) of tetrahydrofuran (THF) using boron trifloride etherate (BF₃ · OEt₂) as initiator and epichlorohydrin (ECH) as promoter. Two kinds of transfer agents were used: methacrylic acid (represented as TA1), and a mixture of methacrylic acid and sodium methacrylate (represented as TA2). The effects of polymerization conditions on molecular weight and molecular weight distribution of macromonomers were studied in this article, when the composition of reactants was kept constant. Under the same conditions, the molecular weight of macromonomer using TA2 is lower than that using TA1, which indicates that TA2 is more active than TA1. The molecular weight of MA‐PTHF macromonomer varies with the polymerization time before transfer agents were added (T1), but molecular weight distribution remains constant. When T1 is limited in 30 min, the apparent number‐average molecular weight of MA‐PTHF increases significantly with the increase of T1, and ranges from 5000 to 18,000. Hence, the molecular weight of MA‐PTHF macromonomer can be controlled by varying T1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 810–815, 2000     

Entropically‐driven ring‐opening polymerization of cyclic butylene terephthalate: Rheology and kinetics

Cyclic butylene terephthalate oligomers (CBT) with ultra‐low melt viscosity can be polymerized into poly (butylene terephthalate) (pCBT) via entropically‐driven ring‐opening polymerization (ED‐ROP) in a short time (ranging from several seconds to 10 min) with no chemical emission and no heat generation during the polymerization process. Due to no heat generation, dynamic rheological measurements were used to monitor the polymerization of CBT from 220 to 250°C. The polymerization was accompanied by a steep increase of the melt viscosity and modulus in isothermal rheological tests, and much faster at higher temperature. With rheological results, reptation theory and Double reptation model were adopted to determine the variation of the molecular weight and concentration with time for pCBT. According to the ED‐ROP mechanism of CBT, kinetics equations were also established to simulate the polymerization process. Furthermore, using the results of variation of molecular weight with time for pCBT and kinetics equations, the polymerization rate constants for initiation and propagation steps were evaluated, and the activation energy was also obtained. It was proved that rheological method is a convenient and reliable way to investigate the kinetics of ED‐ROP of CBT. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Composition and long‐term stability of polyglycidol prepared by cationic ring‐opening polymerization

Polyglycidol synthesized by cationic ring‐opening polymerization of glycidol (boron trifluoride initiation in dichloromethane) was purified of low molecular weight contaminants by centrifugal filtration. The high and low molecular weight fractions were characterized by NMR, GPC, osmometry, viscometry, DSC, and FTIR. The ¹³C‐NMR spectrum of this polymer was completely annotated by proposing a new step in the reaction mechanism. The four thermal dimers of glycidol were also isolated and identified as 2,5‐bis(hydroxymethyl)‐1,4‐dioxane and 2,6‐bis(hydroxymethyl)‐1,4‐dioxane, each of which can exist in cis and trans configurations. Polyglycidol was found to be hygroscopic, picking up about 5% by weight of atmospheric moisture. It was also found that, over time (ca. 1–2 years), polyglycidol crosslinks into a rubbery, insoluble mass. It is therefore recommended that this polymer be stored dry and used within a few months of synthesis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1344–1351, 2004     

Synthesis of PLLA‐PEOMA comb‐block‐comb type molecular brushes based on AGET ATRP and ring‐opening polymerization

BACKGROUND: Molecular brushes are types of macromolecules with densely grafted side chains on a linear backbone. The synthesis of macromolecular brushes has stimulated much interest due to their great potential in applications in various fields. Poly(L ‐lactide)–poly(ethylene glycol) methyl ether methacrylate (PLLA‐PEOMA) comb‐block‐comb molecular brushes with controlled molecular weights and narrow molecular weight distributions were successfully synthesized based on a combination of activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) and ring‐opening polymerization. The synthetic route is a combination of the ‘grafting through’ method for AGET ATRP of the PEOMA comb block and the ‘grafting from’ method for the synthesis of the PLLA comb block. Poly(2‐hydroxyethyl methacrylate) (PHEMA) was synthesized by ATRP, and PLLA side chains and PEOMA side chains were grown from the backbones and the terminal sites of PHEMA, respectively. RESULTS: The number‐average degrees of polymerization of PLLA chains and poly[poly(ethylene glycol) methyl ether methacrylate] (PPEOMA) comb blocks were determined using ¹H NMR spectroscopy, and the apparent molecular weights and molecular weight distributions of the brush molecules were measured using gel permeation chromatography. The crystallization of the components in the comb‐block‐comb copolymers was also investigated. The crystallization of PLLA side chains is influenced by PLLA chain length and the content of PPEOMA in the molecular brushes. The comb‐block‐comb copolymer composed of hydrophobic PLLA and hydrophilic PEOMA can self‐assemble into a micellar structure in aqueous solution. CONCLUSION: A combination of AGET ATRP and ring‐opening polymerization is an efficient method to prepare well‐defined comb‐block‐comb molecular brushes. The physical properties of the molecular brushes are closely related to their structures. Copyright © 2009 Society of Chemical Industry     

Reversibly crosslinked self‐healing PCL‐based networks

Poly(ε‐caprolactone) (PCL)‐based thermoreversible networks with self‐healing properties were prepared through Diels–Alder (DA) and retro‐DA reactions. Bis‐ or Tris‐maleimide compounds and a series of copolymer(caprolactone‐diene) PCL_XF_Y (X: degree of polymerization and Y: furan‐average functionality) with Y between 2.4 and 4.9 were used. The successive sequences of formation and dissociation of polycaprolactone networks via DA and retro‐DA reactions were observed repeatedly by dynamic mechanical analyses (DMA) and their gel‐temperatures determined. The cross‐linking densities, thermal properties, and thermal reversibility of the PCL_XF_Y/multimaleimide polymers have been modulated by the structure and functionalities of the used diene and dienophile moieties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane initiated by potassium isopropoxide

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane (D₄) in bulk initiated by potassium isopropoxide was studied. Several promoters including N‐methyl‐2‐pyrrolidinone (NMP), N,N‐dimethylformamide (DMF), and diglyme were used. It is indicated that the reactions are first‐order in D₄ during the initial stage of polymerization. The polymerization rate of D₄ is influenced by a number of factors, such as the nature of promoters, the molar ratio of promoter to initiator (C_p/C_i ratio), and the reaction temperatures. With the use of NMP as promoter, the polymerization rate constant at 30°C is 10.482 h^?1 with the C_p/C_i ratio equal to 3.0. As the C_p/C_i ratio increases, the polymerization rate constant increases sharply and the cyclic oligomers content in polymer decreases evidently. The back‐biting reaction that leads to the formation of decamethylcyclopentasiloxane (D₅) occurred in the polymerization of D₄. The rate of the D₅ formation relatively to the rate of D₄ conversion increases with the conversion of D₄. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3510–3516, 2006     

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