Cyclopolymerization. VI. Polymerization mechanism of N-methyl-N-allylmethacrylamide at lower temperature

Mechanistic investigations on the polymerization of N-methyl-N-allylmethacrylamide (MAMA) at lower temperature were carried out based upon the ESR studies of MAMA and its monofunctional counterparts irradiated with ⁶⁰Co γ rays. Cyclopolymerizability of MAMA was also studied in connection with the hindered rotation about its amide C? N bond. The propagating radical observed is only related to the methacryl group but not to the allyl group both in MAMA and its monofunctional counterparts. Polymerization at ?78°C yielded a polymer with a lower degree of cyclization(88.8%) as compared with that of polymers formed at higher temperatures (93.5% above 0°C). A structural study revealed that the increment of the unsaturation in the poly-MAMA obtained at ?78°C is due to the allyl group and the content of pendant methacryl group is almost unchanged over the temperature range from ?78 to 120°C. These results led to the conclusion that the polymerization of MAMA at ?78°C proceeds mainly through the methacryl group, the rate-determining step is the cyclization reaction, and, in addition, cyclization reaction scarcely occurs when it polymerizes through the allyl group. Since MAMA is frozen into a glassy state, the effect of glass transition temperature (T_g) has been studied and it was suggested that the polymerization of MAMA proceeds only above T_g.     

Cyclopolymerization. XIX. Effect of N-substituents on cyclopolymerizability of N-allylmethacrylamides

The effect of bulky N-substitutents of N-t-butyl- and N-phenyl-N-allylmethacrylamides (BAMA and PAMA, respectively) on their cyclopolymerizability was investigated. BAMA yielded an almost completely cyclized polymer while the degree of cyclization of poly (PAMA) was about 95%. The latter value indicates that the effect of phenyl group is comparable with that of methyl group, since N-methyl-N-allylmethacrylamide was reported to give a polymer with a degree of cyclization of 93%. Structural investigation on telomerization products of BAMA and PAMA permitted the assignment of the repeating cyclic units of these polymers to that of a five-membered ring. This structural characteristic was also supported by the observation of five-membered cyclized radicals on ESR measurements of these monomers. Rotation around amide C? N bonds of these monomers and related compounds studied by ¹³C-NMR was found to be strongly dependent on N-substitutents. The mechanism of the cyclization was discussed in terms of the structure of the ring formed and rotation around amide C? N bonds of these monomers. The reactivity of the methacryloyl and allyl groups involved in these monomers were compared based on the information obtained by structural investigation of polymers and telomerization products and by ESR studies. © 1993 John Wiley & Sons, Inc.     

Temperature‐sensitive hydrogel microspheres formed by liquid–liquid phase transitions of aqueous solutions of poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate)

Poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate) (DMA‐co‐AMA) copolymers were prepared by the copolymerization of N,N‐dimethylacrylamide with allyl methacrylate (AMA). The methacryloyl group of AMA reacted preferentially, and this resulted in pendant allyl groups along the copolymer chains. Aqueous solutions of these DMA‐co‐AMA copolymers were thermoresponsive and showed liquid–liquid phase transitions at temperatures that depended on the AMA content. Hydrogel microspheres were prepared from these thermally phase‐separated liquid microdroplets by the free‐radical crosslinking of the pendant allyl groups. The morphologies of the resulting thermoresponsive microspheres as a function of the reaction temperature and the amount of the initiator were examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1641–1648, 2005     

Polymerization of allyl esters of unsaturated acids. V. Cyclopolymerization of methyl allyl fumarate

The kinetics of radical polymerization of methyl allyl fumarate (MAF) is discussed in terms of cyclopolymerization and compared with the polymerization results of methyl allyl maleate (MAM) as a cis isomer. In the polymerization of MAF, the rate and degree of polymerization were quite enhanced compared with MAM, and gelation occurred at low conversion. The content of the unreacted allylic double bonds of the MAF polymer was quite large; whereas those of the unreacted fumaric double bonds and the cyclic structural units showed reverse tendencies. Only a slight presence of a five-membered ring was observed in the MAF polymer. The cyclization constants K_A and K_V, the ratios of the rate constants of the unimolecular cyclization reaction to those of the bimolecular propagation reaction of the uncyclized allylic and fumaric radicals, were estimated to be 2.73 and 1.48 mole/liter, respectively. These values suggest the great difference in the cyclopolymerization behavior between two isomeric monomers. These results are discussed in detail in connection with the high reactivity of the fumaric double bond compared to the maleic double bond. In addition, the formation mode and the sequence distribution of the structural units of the polymer produced are discussed on the basis of these analytical results. Thus, for the MAF polymer obtained in the bulk polymerization, about 60% of the cyclic structure can be formed via the intramolecular attack of the uncyclized fumaric radical on the allylic double bond, as opposed to the case of MAM via the predominant intramolecular attack (ca. 90%) of the uncyclized allylic radical on the maleic double bond; these results and the low probability for the succession of cyclic structures and the rather high probability of a vinyl-to-vinyl addition are presented.     

Stereospecific Radical Polymerization of a Side-Chain Transformable Bulky Acrylamide Monomer and Subsequent Post-Polymerization Modification for Syntheses of Isotactic Polyacrylate and Polyacrylamide

We report syntheses of isotactic polyacrylate and polyacrylamide via a stereospecific radical polymerization of a pendant-transformable monomer, acrylamide carrying isopropyl-substituted ureidosulfonamide ( 1 ), followed by post-polymerization modification (PPM). The study in the alcoholysis and aminolysis reactions of the model compound ( 2 ) for evaluation of the transformation ability of the electron-withdrawing pendant group on the repeating unit 1 revealed the following points: the pendant of the polymer became more reactive than that of monomer; the pendant was active enough for aminolysis reaction affording the amide compound quantitatively without additive/catalyst; the addition of a lithium triflate [Li(OTf)] and triethylamine (Et₃N) was effective as for promotion of the alcoholysis reaction. Poly(methyl acrylate) (PMA) was quantitatively obtained via the radical polymerization of 1 in the presence of Li(OTf) at 60 °C and the subsequent addition of methanol along with Et₃N. Thus-obtained PMA showed higher isotacticity [m=74 %] than that directly obtained via radical polymerization of methyl acrylate (MA) (m=51 %). The isotacticity was further increased as the temperature and monomer concentration were lower, and eventually m was increased up to 93 %. The aminolysis PPM after the iso-specific radical polymerization of 1 gave various isotactic polyacrylamides carrying different alkyl pendant groups, including poly(N-isopropylacrylamide) (PNIPAM).     

Polymerization of allyl esters of unsaturated acids. I. Cyclopolymerization of methyl allyl maleate

Radical polymerization of methyl allyl maleate is kinetically discussed in terms of cyclopolymerization using 2,2′-azobisisobutyronitrile (AIBN) as an initiator and benzene as a solvent at 60°C. The ratios of the rate constants of the unimolecular cyclization reaction to those of the bimolecular propagation reaction of the uncyclized allyl and vinyl radicals, K_A and K_V, are estimated to be 9.7 and 1.35 mole/liter by fitting the kinetic equations obtained here to the dependence of the degree of cyclization on monomer concentration, respectively; the large difference between K_A and K_V is also discussed in detail. On the basis of these results the formation mode and the sequence distribution of the structural units of the polymer produced are discussed in detail; thus, for the polymer obtained in the bulk polymerization, about 90% of the cyclic structures can be formed via the intramolecular attack of uncyclized allyl radical on maleic double bond and the probability of succession of the cyclic structural units in diad sequence is exemplified as 0.27.     

Cyclopolymerization. V. Monomer design for the synthesis of highly cyclized polymer from unsymmetrical unconjugated dienes: Synthesis and polymerization of N-methyl-N-allylmethacrylamide

N-Methyl-N-allylmethacrylamide (MAMA) was synthesized and polymerized with radical initiators, and the structure of poly-MAMA was studied, in order to establish the concept that difunctional monomers having monofunctional counterparts which do not polymerize are likely to give rise to highly cyclized polymer, if the cyclized polymer is in a lower free-energy level than the monomer. The cyclopolymerizability of MAMA was considerably higher than that of N-allylmethacrylamide, which was previously reported, and its monofunctional counterpart can be polymerized. The extent of cyclization of poly-MAMA was about 93%, even in the polymer obtained by bulk polymerization. The repeating units of poly-MAMA consist mainly of five-membered rings; six-membered rings and pendent methacryl groups were detected in addition as minor repeating components. The monofunctional counterparts of MAMA, i.e., N-methyl-N-n-propylmethacrylamide (MPMA) and N-methyl-N-allylisobutyramide (MAIA), were also synthesized. Neither MPMA nor MAIA showed any tendency toward polymerization under the same experimental conditions as used for MAMA. The results thus obtained all support the concept mentioned above.     

Bulk atom transfer radical polymerization of allyl methacrylate

A detailed investigation of the polymerization of allyl methacrylate, a typical unsymmetrical divinyl compound containing two types of vinyl groups, methacryloyl and allyl, with quite different reactivities, was performed with atom transfer radical polymerization (ATRP). Homopolymerizations were carried out in bulk, with ethyl‐2‐bromoisobutyrate as the initiator and with copper halide (CuX, where X is Cl or Br) with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst system. Kinetic studies demonstrated that during the early stages of the polymerization, the ATRP process proceeded in a living manner with a low and constant radical concentration. However, as the reaction continued, the increased diffusion resistance restricted the mobility of the catalyst system and interrupted the equilibrium between the growing radicals and dormant species. The obtained poly(allyl methacrylate)s (PAMAs) were characterized with Fourier transform infrared, ¹H NMR, and size exclusion chromatography techniques. The dependence of both the gel point conversion and molecular characteristics of the PAMA prepolymers on different experimental parameters, such as the initiator concentration, polymerization temperature, and type of halide used as the catalyst, was analyzed. These real gel points were compared with the ones calculated according to Gordon's equation under the tentative assumption of equal reactivity for the two types of vinyl groups. Moreover, the microstructure of the prepolymers was the same as that exhibited by those homopolymers prepared by conventional free‐radical polymerization; the fraction of syndiotactic arrangements increased as the reaction temperature was lowered. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2395–2406, 2005     

Polymerization of allyl(vinyl phenyl) ethers and reactions of the resulting polymers

Solution polymerizations of allyl(o-vinyl phenyl)ether and allyl(p-vinyl phenyl)ether with cationic and radical initiators were investigated. Soluble polymers were formed in polymerizations with boron trifluoride etherate and with benzoyl peroxide. In polymerization with azobisisobutyronitrile the polymerization in dilute solution gave a soluble polymer, whereas that in concentrated solution gave a crosslinked, insoluble one. For informationon the polymerization behavior some infrared and ultraviolet spectroscopic investigations of the soluble polymers were made. From these results it appears that polymers with pendant allyl groups are formed in polymerization with boron trifluoride etherate at low temperature, and polymers containing pendant vinyl groups and allyl groups are obtained with the two types of radical initiator. Copolymerizations of these monomers with ethyl vinyl ether and styrene with the use of boron trifluoride etherate were sucessfully effected. Such reactions as Claisen rearrangement, crosslinking induced with radical initiators, and epoxidation with perbenzoic acid were examined for the polymers prepared in the polymerization with boron trifluoride etherate. Good results were obtained for the former two reactions. However, the latter was unsuccessful.     

Synthesis of 2-Methacryloyl-5-hydroxy-3,3,5-trimethylisoxazolidine and Copolymers Thereof

Previously unknown 2-methacryloyl-5-hydroxy-3,3,5-trimethylisoxazolidine was prepared by the reaction of 5-hydroxy-3,3,5-trimethylisoxazolidine with methacryloyl chloride. Homopolymers of this compound and its copolymers with N-vinylformamide and N-vinylpyrrolidone were obtained by radical polymerization.     

Synthesis of polyphosphodiesters by ring‐opening polymerization of cyclic phosphates bearing allyl phosphoester protecting groups

The allyl phosphoester group is shown to be a protecting group for the synthesis of anionic polyphosphodiesters. Our strategy relies on the synthesis of a cyclic phosphate monomer bearing a pendant allyl phosphoester group, its easy purification by fractional distillation, its organocatalyzed ring‐opening polymerization by 1,8‐diazobicyclo[5.4.0]undec‐7‐ene (DBU) and 1‐[3,5‐bis(trifluoromethyl)phenyl]‐3‐cyclohexyl‐thiourea (TU). Finally, the deprotection of the allyl phosphoester group is carried out by reaction with sodium benzenethiolate in the absence of any detectable degradation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2642–2648     

Preparation of novel macromonomers and study of their polymerization

Novel macromonomers of polystyrene and poly(tert‐butyl acrylate) containing a methacryloyl group as a polymerizable unit and two chains of the same length were prepared in two steps: the synthesis of the precursors through the atom transfer radical polymerization of styrene and tert‐butyl acrylate initiated by 1‐hydroxymethyl‐1,1‐di[(2‐bromoisobutyryloxy)methyl] ethane and the esterification of the hydroxyl group in the precursors with methacryloyl chloride. The molecular weight and polydispersity of the macromonomers were controllable because of the living nature of the atom transfer radical polymerization. Gel permeation chromatography, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and hydrolysis confirmed the structure of the novel macromonomers. The homopolymerization and copolymerization of the macromonomers were investigated to prepare branched copolymers in which two chains were grafted from every repeating unit. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3887–3896, 2004     

Synthesis of polymers by template polymerization. I. Template polymerization of poly(methacrylic acid) with β‐cyclodextrin

A novel template monomer with multiple methacryloyl groups was synthesized with β‐cyclodextrin by the acetylation of primary hydroxyl groups and the esterification of secondary hydroxyl groups with methacrylic acid anhydride. The average number of methacryloyl groups in the monomer was 11. The radical polymerization of the monomer was carried out with the following initiators: α,α′‐azobisisobutylonitrile, H₂O₂? Fe²⁺ redox initiator, p‐xylyl‐N,N‐dimethyldithiocarbamate (XDC), and α‐bromo‐p‐xylyl‐N,N‐dimethyldithiocarbamate (BXDC). When the concentration of the monomer was less than 4.12 × 10^?3 M, polymerization was limited inside the molecule, and gelation of the system was hindered. For controlled radical photopolymerization with XDC and BXDC, the methacryloyl groups of the monomer were homogeneously polymerized, and poly(methacrylic acid) with a narrow molecular weight distribution was obtained by the hydrolysis of the polymerized products. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3539–3546, 2001     

Radical cyclopolymerizations of diallylsilanes and triallylsilanes

The radical polymerizations of diallylsilanes such as diallyldimethylsilane ( 1 ) and diallylmethylphenylsilane ( 2 ) have been conducted. Both poly(diallyldimethylsilane) ( 3 ) and poly(diallylmethylphenylsilane) ( 4 ) are soluble in benzene, methyl ethyl keton (MEK), and chloroform, slightly soluble in acetone, and insoluble in methanol and ethanol. No insoluble fraction of either polymer was obtained. Very little evidence of vinyl protons in the ¹H-NMR spectra can indicate that both polymerizations predominantly proceed with intramolecular cyclization. In order to study the ring size of cyclic structure in the repeating unit of the polymers, a model compound, allyl(2-chloropropyl)dimethylsilane ( 5 ), was synthesized and cyclized with Bu₃SnH in the presence of azobisisobutyronitrile (AIBN) in benzene, under similar condition of those for the cyclopolymerizations. The product was analyzed with GC–MS which showed that the five-membered ring compound, 1,1,3,4-tetramethylsilacyclopentane, was not formed. From the result of the cyclization of the model compound, it can be suggested that the polymerizations undergo with only h–t intramolecular cyclization to form a six-membered ring in the repeated unit. The ¹³C-NMR spectra of 3 and 4 were measured to study the ring size and the configuration of the cyclic structures. The two peaks at ?1.6 and ?3.4 ppm of the spectrum of 3 show that there are two kinds of methyl carbons in the repeating unit. From consideration of the model reaction and the number of the peaks of the NMR spectrum, it can be considered that the polymer main chain is assembled with the six-membered ring in cis-form, and the two signals are assigned to equatorial and axial methyl carbons, respectively. The two peaks at -1.5 and -5.1 ppm of the ¹³C-NMR spectrum of 4 can be assigned similarly. The radical cyclopolymerizations of triallylsilanes such as methyltriallylsilane ( 6 ) and phenyltriallylsilane ( 7 ) were conducted. The ¹H-NMR spectra of poly(methyltriallylsilane) ( 8 ) and poly(phenyltriallylsilane) ( 9 ) show broad peak around 5 ppm for vinyl protons and around 2 ppm for alkyl protons. Comparisons of the relative intensities of the peaks indicate that both polymerizations undergo with single ring closure to form a polymer with monocyclic structure moiety, cyclosilahexane, and an allyl group in a repeating unit of 8 and 9 .     

Polymerization of alkyl allyl oxalates in the evolution of carbon dioxide at elevated temperatures

Radical polymerization of several alkyl allyl oxalates, including methyl allyl oxalate (MAO), ethyl allyl oxalate, propyl allyl oxalate, butyl allyl oxalate, and octyl allyl oxalate, was conducted in the evolution of carbon dioxide at elevated temperatures, and was compared with the anomalous polymerization behavior of diallyl oxalate (DAO) discussed in our earlier article

1 A. Matsumoto, I. Tamura, M. Yamawaki, and M. Oiwa, J. Polym. Sci. Polym. Chem. Ed., 17 , 1419 (1979).

. The kinetic equations for the polymerization of alkyl allyl oxalate were derived following the kinetic treatment of the DAO polymerization by further consideration of the absence of cyclization of the growing polymer radical and the effective reinitiation by alkyl radical, and were then satisfactorily applied to the polymerization of MAO, as a representative alkyl allyl oxalate. The evolution of carbon dioxide in the polymerization of alkyl allyl oxalates was enhanced with the increase of bulkiness of the alkyl substituent, as a result of steric suppression of the propagation of the growing polymer radical.     

Preparation of a copolymer of methyl methacrylate and 2‐(dimethylamino)ethyl methacrylate with pendant 4‐benzyloxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy and its initiation of the graft polymerization of styrene by a controlled radical mechanism

The macroinitiator of a copolymer (PMD_BTM) of methyl methacrylate (MMA) and 2‐(dimethylamino)ethyl methacrylate (DAMA) with 4‐benzyloxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (BTEMPO) pendant groups was prepared by the photochemical reaction of tertiary amine groups of the copolymer with benzophenone in the presence of BTEMPO. The radical copolymerization of MMA and DAMA was carried out first with azo‐bis‐isobutyronitrile (AIBN) as an initiator; then, the dimethylamine groups of the copolymer constituted a charge‐transfer complex with benzophenone under UV irradiation, and the methylene of ternary amine and diphenyl methanol radicals were produced. The former was capped by BTEMPO, and the nitroxide (BTEMPO) was attached to the polymeric backbone. The amount of pendant BTEMPO on PMD_BTM was measured by ¹H NMR. PMD_BTM initiated the graft polymerization of styrene via a controlled radical mechanism, and the molecular weight of the PMD‐g‐polystyrene increased with the polymerization time. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 604–612, 2001     

Ring‐opening polymerization of 6‐hydroxynon‐8‐enoic acid lactone: Novel biodegradable copolymers containing allyl pendent groups

This article reports the synthesis and copolymerization of 6‐hydroxynon‐8‐enoic acid lactone. The ring‐opening polymerization of this lactone‐type monomer bearing a pendant allyl group led to new homopolymers and random copolymers with ε‐caprolactone and L ,L ‐lactide. The copolymerizations were carried out at 110 °C with Sn(Oct)₂ as a catalyst. The introduction of unsaturations into the aliphatic polyester permitted us to carry out different chemical transformations on this family of polymers. For example, this article reports the bromination, epoxidation, and hydrosylilation of the allyl group in the new polyester copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 870–875, 2000     

Synthesis of phosphate‐pendant polymers and their application to thermally latent polymeric initiators

A novel phosphate monomer, O‐p‐(methacryloyloxymethyl)benzyl O,O‐diethyl phosphate (MDP) was synthesized by the reaction of diethyl phosphorochloridate with 1,4‐benzenedimethanol, followed by the reaction with methacryloyl chloride in the presence of triethylamine. The radical polymerization of MDP and copolymerization with methyl methacrylate were carried out in the presence of 2,2′‐azobisisobutyronitrile (3 mol %) in dimethylacetamide at 60 °C for 20 h to afford phosphate‐pendant polymers. The polymerization of glycidyl phenyl ether (GPE) was carried out with the phosphate‐pendant polymer as an initiator in the presence of ZnCl₂. The polymerization did not proceed below 90 °C but rapidly proceeded above 90 °C to afford polyGPE. The phosphate‐pendant polymer served as a good thermally latent polymeric initiator. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3365–3370, 2001     

Polymerization of allyl esters of unsaturated acids. IX. Controlled ring closure in the radical cyclopolymerization of allyl methacrylate

Radical cyclopolymerization of allyl methacrylate (AMA) was investigated in detail, especially under the specified conditions; that is, above the ceiling temperature for a head-to-tail propagation (ΔG_ht ≥ 0) in the polymerization of methacrylate. Thus the structure of the polymer obtained was examined by ¹H- and ¹³C-NMR and infrared (IR) spectroscopy; no existence of unreacted pendant methacrylyl groups was observed, which suggests that, as a cyclopolymerization mechanism of AMA, intermolecular propagation of growing radicals, followed by intramolecular cyclization or intermolecular propagation of the resulting uncyclized methacrylyl radical, occurs exclusively with methacrylyl group. Temperature dependency of cyclization constant K_c was unusual; K_c increased rapidly at elevated temperatures and no linear relationship of ln K_c vs. 1/T was observed. Five-membered ring formation was favored at an elevated temperature and diluted monomer concentration. These results are discussed thermodynamically in terms of controlled ring closure in cyclopolymerization.     

Cyclization tendencies in the free radical polymerization of allyl acrylate derivatives: A computational study

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 α‐[(allyloxy)methyl]acrylate. The models used in this study have revealed the fact that while methyl α‐[(allyloxy)methyl]acrylate, cyclopolymerizes via 5‐membered rings, AMA and ACA do not. The cyclization tendency of methyl α‐[(allyloxy)methyl]acrylate is attributed to the similar hybridization (sp³) 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. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011