Reactivity Study of Elementary Steps in the Polymerization Mechanism of Acrylfuranic Compounds by Frontier Molecular Orbital Theory (original) (raw)
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Activity of the furfuryl ring in the free radical polymerization of acrylic monomers
Journal of Polymer Science Part A-polymer Chemistry, 1996
The effect and the participation of the furfuryl ring, in particular the hydrogen at position C-5 in the free radical polymerization are analyzed following the polymerization of furfuryl acrylate (FA) and furfuryl methacrylate (FM) initiated by AIBN under photochemical activation. The results obtained indicate that the polymerization of FA deviates from the classical free radical kinetic scheme, giving rise to crosslinked polymers even at a degree of conversion lower than 7%. This behavior is well explained taking into consideration the participation of the furfuryl ring which acts as a degradative transfer agent. This was demonstrated by the kinetic analysis of the free radical polymerization of MMA initiated by the thermal decomposition of AIBN in the presence of different concentrations of furfuryl acetate.
Free radical copolymerization of furfuryl acrylate and 2-hydroxyethyl-methacrylate
Journal of Polymer Science Part A: Polymer Chemistry, 1993
Copolymers of furfuryl acrylate (F) and 2-hydroxyethyl methacrylate (H) were prepared by free radical polymerization in DMF solution at 50°C, using 2,2'-azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of both monomers were calculated according to the general copolymerization equation using the Fineman-Ross and Kelen-Tudos linearization methods, as well as the Tidwell and Mortimer nonlinear least-squares treatment. The reactivity ratios obtained were rF = 0.93 and rH = 1.42. The microstructure of copolymer chains is described on the basis of first-order Markov statistics, and the copolymer glass transition temperatures were determined calorimetrically. The variation of Tg with the copolymer composition is discussed according to modern methods, considering the sequence distribution of monomeric units along the copolymer chains. Also the Tg of the corresponding homopolymers was determined giving the values Tg(F) = 321 K and T,(H) = 358 K, whereas the Tg of the corresponding alternating diad has an average value of Tg~m = 326 K.
Modeling the free radical polymerization of acrylates
International Journal of Quantum Chemistry, 2005
Acrylates have gained importance because of their ease of conversion to high-molecular-weight polymers and their broad industrial use. Methyl methacrylate (MMA) is a well-known monomer for free radical polymerization, but its ␣-methyl substituent restricts the chemical modification of the monomer and therefore the properties of the resulting polymer. The presence of a heteroatom in the methyl group is known to increase the polymerizability of MMA. Methyl ␣-hydroxymethylacrylate (MHMA), methyl ␣-methoxymethylacrylate (MC 1 MA), methyl ␣-acetoxymethylacrylate (MAcMA) show even better conversions to high-molecular-weight polymers than MMA. In contrast, the polymerization rate is known to decrease as the methyl group is replaced by ethyl in ethyl ␣-hydroxymethylacrylate (EHMA) and t-butyl in t-butyl ␣-hydroxymethylacrylate (TBHMA). In this study, quantum mechanical tools (B3LYP/6-31G*) have been used in order to understand the mechanistic behavior of the free radical polymerization reactions of acrylates. The polymerization rates of MMA, MHMA, MC 1 MA, MAcMA, EHMA, TBHMA, MC 1 AN (␣-methoxymethyl acrylonitrile), and MC 1 AA (␣-methoxymethyl acrylic acid) have been evaluated and rationalized. Simple monomers such as allyl alcohol (AA) and allyl chloride (AC) have also been modeled for comparative purposes.
Journal of Polymer Science Part A: Polymer Chemistry, 2011
In this study density functional theory (DFT) has been used to model the elementary steps and rationalize the free radical polymerization kinetics in allyl methacrylate (AMA), allyl 2-cyanoacrylate (ACA) and methyl a-[(allyloxy)methyl]acrylate. The models used in this study have revealed the fact that while methyl a-[(allyloxy)methyl]acrylate, cyclopolymerizes via 5-membered rings, AMA and ACA do not. The cyclization tendency of methyl a-[(allyloxy)methyl]acrylate is attributed to the similar hybridization (sp 3) of C3 and C5 favoring a quasi cyclic structure for the reactive rotamer. On the other hand, the presence of the cyano (CN) group in ACA facilitates the initiation step as compared to AMA. The chain transfer reaction does not seem to play a major role in the monomers of interest. This study highlights the usage of quantum chemistry in determining the cyclization tendencies of allyl acrylate derivatives in their free radical polymerization reactions. V
The radical polymerization of methacrylic acid, acrylic acid and acrylamide in aqueous solution has been investigated. Detailed kinetic models for both acrylic acid, AA, and methacrylic acid, MAA, have been developed applying the program PREDICI TM. Good representation of experimental conversion vs. time profiles and molar mass distributions as well as, in case of AA, the branching level could be achieved. The polymerization of MAA has been studied at 35 and 50 °C with focus on the influence of 2-mercaptoethanol, ME, as chain transfer agent, CTA, on reaction kinetics. The rate coefficient of transfer to CTA, tr,CTA , k was measured for different monomer levels by the Mayo and the chain length distribution procedure. The ratio of tr,CTA k to the propagation rate coefficient, p k , is independent of monomer to water ratio while both rate coefficients increase by approximately one order of magnitude in passing from bulk to dilute aqueous solution. It was found that addition of CTA reduces the rate of MAA polymerization by two effects on t. k At negligible monomer conversion, t k increases towards higher content of CTA, because average chain length is reduced by the CTA. Chain-length dependent termination may be represented by adopting the composite model, which is a well-established theory to describe chain-length dependency of termination of macroradicals of identical size. The composite model could be applied to average chain length. The reduction of t k towards higher degrees of monomer conversion
Controlled Radical Polymerization of Furfuryl Methacrylate
Macromolecular Symposia, 2006
Atom transfer radical polymerization provides a new method of controlled radical polymerization. The most important advantage of ATRP is that it is tolerant to the different functional groups present in the initiator as well as in the monomer. Furfuryl Methacrylate (FMA) is a specialty monomer, which has applications in coatings, adhesives and in biomedicals. Conventional radical polymerization of FMA leads to excessive gel formation, which limits its applications. In this investigation homo and co-polymerization of FMA has been carried out via ATRP. ATRP of FMA was carried out using CuBr as catalyst and 1, 1, 4, 7, 10, 10 hexamethyltriethylenetetramine (HMTETA) as ligand. There was no gel formation during the polymerization. ATRP of FMA was well controlled with a linear increase of molecular weight (Mn) with monomer conversion. The polymers were characterized by using 1 HNMR, FT-IR and GPC analysis. Interestingly, it was observed that the furfuryl ring was not affected during polymerization.
Atom Transfer Radical Polymerization of Isobornyl Acrylate: A Kinetic Modeling Study
Macromolecules, 2010
A detailed kinetic modeling study of the atom transfer radical polymerization (ATRP) of isobornyl acrylate (iBoA) is presented. This study combines a detailed reaction scheme with a systematic approach to account for diffusional limitations. Calculated values for diffusion coefficients and the Williams-Landel-Ferry parameters for poly(iBoA) are based on rheological measurements. A good agreement with experimental data is obtained for the polymerization rate, average chain length, and polydispersity index in conditions ranging from 323 to 348 K for targeted chain lengths varying from 50 to 100 and initial activator/deactivator concentrations between 10-50/0-2.5 mol m-3. In these conditions, βC-scission reactions are insignificant and backbiting reactions result in a slight decrease of the polymerization rate and level of control at high conversions only. Termination is subject to diffusional limitations during the whole ATRP, while diffusional limitations on deactivation cannot be neglected at higher conversion. Diffusional limitations are shown to be codetermined by the evolution of the chain length distribution of both the end-chain and mid-chain macromolecular species.
Macromolecular Theory and Simulations, 2012
The formation kinetics and structure of three-dimensional networks in free radical polymerization of FM thermally initiated at high temperature are studied by analysis of zero and first-order moments of molecular size distribution of primary chains (MSDPC) in the networks. Zero-order moment values of MSDPC reveal that the system elapses as a living radical polymerization. Also, by means of the analysis of these moments and the first-order ones of MSDPC, the sigmoidal shape of polymerization kinetic curves can be explained. On the other hand, the results of average crosslink density obtained using moment values of MSDPC suggest that this parameter does not change with polymerization temperature.