Reaction of the benzoyloxy radical with α-methylstyrene

Benzoyl peroxide labelled with carbon-14 and tritium has been used for study of the end-groups in copolymers of α-methylstyrene (MST) with methyl methacrylate, in particular determination of the relative numbers of benzoate and phenyl end-groups derived from the initiator. MST is found to be quite reactive towards the benzoyloxy radical. It is deduced that combination is the dominant mode of termination in the copolymerization, that transfer reactions are not important and that there is little abstraction of hydrogen from MST by the benzoyloxy radical.     

Evaluation of end groups in poly(methyl methacrylate-co-styrene) by 13C NMR

Summary The carbonyls of the various benzoate end groups in poly(methyl methacrylate-co-styrene) prepared with benzoyl-carbonyl-¹³C peroxide give rise to discrete and characteristic signals in the 62.9 MHz ¹³C NMR spectra of the copolymers. Thus, by integration of the spectra, it is possible to estimate the relative reactivity of benzoyloxy radicals towards styrene and methyl methacrylate. In addition, information on the amount of initiator consumed in other processes such as transfer to initiator and primary radical termination can be obtained.     

The reactivity towards the benzoyloxy radical of 1,4-bis(2-methylstyryl)benzene

It has been found that 1,4-bis(2-methylstyryl)benzene (MSB) is 520 times as effective as methyl methacrylate in capturing the benzoyloxy radicals generated at 60°C by dissociation of benzoyl peroxide. This result has been obtained from examinations of the end groups in samples of poly(methyl methacrylate) prepared using benzoyl peroxide as initiator in the presence of MSB at low concentrations.     

Effects of some unsaturated nitrogen-heterocycles on the polymerization of methyl methacrylate initiated by benzoyl peroxide

Summary The rate of polymerization at 60°C of methyl methacrylate initiated by benzoyl peroxide is almost unaffected by the presence of a small amount of 4-styrylpyridazine, 1-(2-pyridyl)-2-(4-pyridyl)ethylene or 2,6-distyrylpyridine. Examination of polymers made using peroxide suitably labeled with carbon-14 and tritium shows that these additives increase the ratio of benzcate to phenyl end-groups derived from the initiator. This effect arises because the additives are effective in capturing the benzoyloxy radical; in this respect, they are however considerably less reactive than the corresponding compounds containing groups derived from benzene in place of the nitrogen heterocycles.     

End-groups in poly(methyl methacrylate) and polystyrene prepared by radical polymerization in the presence of derivatives of stilbene

Polymers of methyl methacrylate and styrene have been prepared in the presence of low concentrations of various para-derivatives of stilbene, using ¹³C-benzoyl peroxide as the source of the initiating radicals. Examination of the ¹³C-NMR signals due to benzoate end-groups showed that in each case a high proportion of the initiator fragments was attached to a stilbene unit. The results indicate that each of the stilbenes has very high reactivity towards the benzoyloxy radical, depending upon the nature of the substituent. Radical polymerization involving benzoyl peroxide and a stilbene provides a method for the preparation of polymers with special end-groups.     

The reactivities towards the benzoyloxy radical of various isomers of fluorostilbene

Summary The rate constants at 60°C for the reactions of the benzoyloxy radical with methyl methacrylate, the E-isomers of 2-, 3- and 4-fluorostilbene and the Z-isomer of 4-fluorostilbene have relative values of 1, 41, 17, 18 and 14 respectively. These results were obtained from work involving analyses for the benzoate and phenyl end-groups in polymers of methyl methacrylate, prepared using benzoyl peroxide suitably labelled with carbon-14 and tritium using each of the fluorostilbenes in turn as an additive in a polymerization.     

Modification of pristine multiwalled carbon nanotube by grafting with poly(methyl methacrylate) using benzoyl peroxide initiator

Multiwalled carbon nanotube was successfully grafted with poly(methyl methacrylate) by free radical mechanism using benzoyl peroxide initiator. The reaction was carried out in situ, where the initiator and methyl methacrylate monomer generated the polymer‐free radical that was subsequently grafted to the surface of the pristine multiwalled carbon nanotube. The multiwalled carbon nanotube grafted poly(methyl methacrylate) (MWCNT‐g‐PMMA) were characterized using Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, ¹³ C‐solid NMR spectroscopy, X‐ray photoelectron spectroscopy, and scan electron microscopy. From the result of the characterizations, the grafting of poly(methyl methacrylate) on to multiwalled carbon nanotube was confirmed, and a percentage grafting of 41.51% weight was achieved under optimized conditions with respect to the temperature and the amount of the initiator. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43270.     

四官能度过氧化物JWEB50引发的PS-b-PMMA合成与表征

引言嵌段共聚物是具有两种或两种以上不同链段的聚合物,不同链段间存在的化学键限制了聚合物的相分离程度,易形成微相分离结构[1],而嵌段共聚物能作为聚合物共混体系的相容剂,只需加入少量     

Effect of shear rate on the rate of polymerization of styrene

Application of shear was found to have considerable effect on the radical polymerization of styrene initiated by benzoyl peroxide. The initial rate of polymerization decreases by as much as 30% for low shear rates (γ), but on further increasing γ it increases slightly, levelling ultimately at the 10% reduction level. The effect of solvent was shown to have negligible effect, in direct contrast to that observed by Kumar et al.^1–3 for methyl methacrylate and acrylonitrile. Experiments confirm that the reduction in the rate of initial polymerization can be attributed largely to the change in initiator efficiency on the application of shear rate. As a further test, the decomposition rate of benzoyl peroxide in nitrobenzene at 80°C was measured and was found to increase significantly on application of shear. This confirms the importance of mass transfer resistance in removal of CO₂. The reduction in the rate of polymerization of styrene can now be explained as follows. In the reaction mass, there are benzoyloxy as well as phenyl radicals and styrene molecules have been shown by Bevington⁴ to react preferentially with the former. The fall in the rate of polymerization of styrene occurs because, on the application of shear, decomposition of benzoyloxy radicals is favoured in the forward direction and its concentration in the reaction mass falls. As a result the initiation of polymer radicals reduces, which in turn gives a lower rate of polymerization.     

聚丙烯表面附着促进剂的合成与表征

以氯化聚丙烯为大分子引发剂,以FeCl2作为催化剂,利用原子转移自由基聚合制备一种聚丙烯表面附着促进剂,聚丙烯/聚甲基丙烯酸甲酯接枝共聚物,利用红外、热重及差热分析对其进行表征.实验发现,在很低的加量下,聚丙烯表面附着促进剂可以显著提高丙烯酸树脂对聚丙烯的附着.     

Effects of 1,2,3-triphenylcyclopropene on radical polymerizations

Summary 1,2,3-Triphenylcyclopropene (TPCP) is a powerful retarder for polymerizations of methyl methacrylate (MMA) and styrene initiated by benzoyl peroxide or azobisisobutyronitrile. End-groups in polymers of MMA were studied by 13C-NMR spectroscopy and also, in the case of the peroxide, by using radioactive initiator. It was shown that, towards the benzoyloxy and 1-cyano-1-methylethyl radicals, the reactivity of TPCP exceeds that of MMA by factors of about 60 and three respectively at 60°C. TPCP can be used to introduce into polymers end-groups of special types.     

Atom transfer radical polymerization of methyl methacrylate induced by an initiator derived from an ionic liquid

An ionic liquid, 1‐(2‐bromoisobutyryloxyethyl)‐3‐methylimidazolium hexafluorophosphate, was synthesized to act as the initiator of the atom transfer radical polymerization of methyl methacrylate (MMA). By a combination with CuBr and pentamethyldiethylenetriamine, the ionic liquid initiated the free radical polymerization of MMA to proceed in a controlled way over a wide temperature range of 0 to 60 °C. The number‐average molecular weight of the poly(methyl methacrylate) (PMMA) increased with monomer conversion and the polydispersity was relatively narrow. End‐group analysis by proton NMR indicated the presence of the initiator fragments at the ends of the polymer main chain. Lowering the reaction temperature had the result of increasing the content of rr triads. The glass transition temperature was higher for PMMA obtained at lower temperature than at higher temperature. The solubility of the PMMA in methanol increased with the incorporation of imidazolium groups in the polymer. Copyright © 2006 Society of Chemical Industry     

Well-defined dibenzocyclooctyne end functionalized polymers from atom transfer radical polymerization

The dibenzocyclooctyne end functionalized agent 1 was designed as atom transfer radical polymerization (ATRP) initiator. The ATRP was then explored on three types of monomers widely used in free radical polymerization: methyl methacrylate, styrene, and acrylates (n-butyl acrylate and tert-butyl acrylate). The living polymerization behaviors were obtained for the methyl methacrylate and styrene monomers. The SPAAC click reactivity of dibenzocyclooctyne end group were demonstrated by successfully reacting with azide functionalized small chemical agents and polymers. Various topological polymers such as block and brush polymers were produced from strain-promoted azide-alkyne cycloaddition reaction (SPAAC) using the resultant dibenzocyclooctyne end functionalized poly(methyl methacrylate)/polystyrene as building blocks. For the acrylates, however, the polymerization did not hold the living characteristics with the dibenzocyclooctyne end functionalized ATRP initiator 1.     

Block copolymers obtained by free radical mechanism III. Synthesis in emulsion

Block copolymers were synthesized by a sequential free radical polymerization method with the use of di-t-butyl-4,4′-azobis(4-cyanoperoxyvalerate) as the trifunctional initiator. The polymerizations were carried out in two stages. First, the poly(methyl methacrylate) and poly(butyl methacrylate) polymeric initiators were synthesized by activating, at room temperature, the perester groups of the initiator with tetraethylenepentamine. For the second stage, the reaction ingredients were pre-emulsified, then the azo groups of these polymeric initiators were activated thermally in the presence of either styrene or p-methylstyrene. It was found that the reaction in the emulsion particles followed bulk kinetics, although the average size of the particles was small, 50–100 nm.     

ICAR ATRP of methyl methacrylate catalyzed by FeCl3·6H2O/succinic acid

In this work, methyl methacrylate (MMA) was polymerized by initiator for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) method to obtain low molecular weight living polymers. The ATRP initiator was ethyl 2‐bromoisobutyrate, the catalyst ligand complex system was FeCl₃·6H₂O/succinic acid, and the conventional radical initiator 2,2′‐azobisisobutyronitrile was used as a thermal radical initiator. Polymers with controlled molecular weight were obtained with ppm level of Fe catalyst complex at 90°C in N,N‐dimethylformamide. The polymer was characterized by nuclear magnetic resonance (NMR). The molecular weight and molecular weight distribution of the obtained poly (methyl methacrylate) were measured by gel permeation chromatography method. The kinetics results indicated that ICAR ATRP of MMA was a “living”/controlled polymerization, corresponding to a linear increase of molecular weights with the increasing of monomer conversion and a relatively narrow polydispersities index. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetics of Phase Transfer Agent-aided Free–Radical Polymerization of Acrylonitrile and Methyl Methacrylate Using Water-Soluble Initiator

This paper deals with the kinetics of radical polymerization of acrylonitrile (AN) and methyl methacrylate (MMA), using water-soluble potassium peroxydisulphate initiator in the presence of cetyldimethylbenzylammonium chloride (PTC), at 60°C under oxygen-free atmosphere. The role of concentrations of monomer, initiator, catalyst and temperature on the rate of polymerization were ascertained. Based on the results obtained, a suitable kinetic scheme has been proposed to account for the experimental observation.     

Polysoap-induced polymerization of methyl methacrylate and styrene by poly(sodium alkyl 2-hydroxy-3-methacryloyloxypropyl phosphate)s in water

Summary Poly(sodium alkyl 2-hydroxy-3-methacryloyloxypropyl phosphate)s as polysoap induced the radical polymerization of methyl methacrylate and styrene in the absence of an added radical initiator in water at 80°C. The polysoap having a C₁₄ alkyl group showed the highest activity of all tested groups. The generalized initiation mechanism of the spontaneous polymerization in which the micellar aggregation state participates is discussed.     

End-groups in polymers of 2-vinylnaphthalene and 4-vinylbiphenyl,prepared by polymerisations initiated by azobis(isobutyronitrile)

Polymerisations of 2-vinylnaphthalene and 4-vinylbiphenyl and copolymerisations of these monomers with methyl methacrylate have been initiated by azobis(isobutyronitrile) enriched in its methyl groups with carbon-13. The environments of (CH₃)₂C(CN)- end-groups in the copolymers have been examined by ¹³C nuclear magnetic resonance. It has been concluded that both aromatic monomers are more than twice as reactive as methyl methacrylate towards the primary radical.     

Graft copolymerization onto starch. I. Complexes of Mn3+ as initiators

Advantages in using the pyrophosphate complex of trivalent managanese over the sulfate complex as initiator for graft copolymerization onto starch are discussed. The first successful attempts to graft copolymerize acrylonitrile, methyl methacrylate, and acrylamide to starch and starch derivatives are described using managanic pyrophosphate as initiator. Selective solvent extraction of the reaction products and very low conversions of monomer to homopolymer in absence of starch substrates provide evidence for high grafting efficiencies obtained with acrylonitrile and methyl methacrylate. With acrylamide as monomer, however, low grafting efficiencies and considerable amounts of homopolymer are obtained under the experimental conditions investigated. Reaction mechanisms responsible for initiation of graft copolymerization are discussed. These are (a) glycol cleavage in the anhydroglucose units by Mn³⁺ ions leading to formation of a radical, and (b) enolization and further oxidation of oxidized starch by Mn³⁺ ions also leading to radical species. Mechanisms are also proposed for homopolymerization through Mn³⁺ oxidation of enols which probably are formed by “vinylogous” addition of water molecules to acrylamide and methyl methacrylate.     

New peracid-type polymeric initiator for radical polymerization

In this study, a radiation-induced copolymer, namely polyethylene-g-acrylic acid powder, was used, whose carboxyl groups can be oxidized to form a highly reactive polymer initiator. The activation energy for its decomposition is 22.4 kcal/mol. It was found that the peracid-type polymeric powder was effective as an initiator for radical polymerization. It had high reactivity toward 2-hydroxyethyl methacrylate (HEMA), which could be easily grafted onto the polymeric powder; also, the homopolymer could be obtained. The kinetic investigation indicated that this polymerization proceeded by a radial mechanism, and the overall activation energy of homopolymerization was 18.67 kcal/mol and the overall activation energy of bigraft polymerization was 17.35 kcal/mol. By using the peracid-type polymeric powder as initiator for the copolymerization of methyl methacrylate with styrene, it was confirmed that the polymerization initiated by the peracid-type polymeric powder was a radical reaction.