Grafting of maleic anhydride on polyethylene. I. Mechanism of grafting in a heterogeneous medium in the presence of radical initiators

Polyethylene has been grafted with maleic anhydride, as proved by the infrared spectra and the properties of the grafted films. The influence of oxygen and a comparison of the effectiveness of benzoyl peroxide and AIBN showed that polyethylene macroradicals are formed through the decomposition of hydroperoxide and peroxide groups. Side chains of poly(maleic anhydride) are formed by a combination of polyethylene macroradicals with those of poly(maleic anhydride). This mechanism of reaction was confirmed by the influence of the amount of film, the initiator and monomer concentrations, and temperature on the percentage of grafting.     

Grafting of maleic anhydride on polyethylene. III. Influence of polyethylene concentration on the course of the reaction in a homogeneous medium

The effect of the polymer concentration on the grafting of maleic anhydride on polyethylene was studied at different temperatures and at different monomer and initiator concentration. The character of the curves obtained suggests the importance of the termination reactions and the appearance of the gel effect at higher polymer concentrations.     

Peroxide-catalyzed grafting of maleic anhydride onto molten polyethylene in the presence of polar organic compounds

The crosslinking of LDPE resulting from reaction with dicumyl peroxide at 180°C is increased in the presence of maleic anhydride (MAH). The presence of electron-donating nitrogen-containing compounds (amides, lactams, disubstituted aromatic amines, and amine oxides), phosphorous-containing compounds (phosphites, phosphates, phosphonates, phosphoramides, and phosphine oxides) and sulfur-containing compounds (sulfoxides, aryl disulfides, and thiazyl disulfides) which inhibit the homopolymerization of MAH but not that of methyl methacrylate, prevents crosslinking and yields soluble PE containing MAH units. Crosslinking, due to coupling of PE^˙ macroradicals formed by hydrogen abstraction from PE by excited MAH, is prevented by electron donation from the additive to the MAH⁺ cation which is present in the MAH+?MAH excimer as well as in the excimer which is appended to the PE.     

Grafting in reaction of polyethylene and poly(maleic anhydride)

Polyethylene has been grafted in a reaction with poly(maleic anhydride) in the presence of radical initiators. The role of oxygen, the comparison of the effectiveness of benzoyl peroxide and AIBN, and the kinetics of the reaction suggest that side chains are formed via a combination of the macroradicals of both polymers.     

Grafting of maleic anhydride onto linear polyethylene: A Monte Carlo study

Monte Carlo simulation was used to study the graft of maleic anhydride (MAH) onto linear polyethylene (PE‐g‐MAH) initiated by dicumyl peroxide (DCP). Simulation results revealed that major MAH monomers attached onto PE chains as branched graft at higher MAH content. However, at extremely low MAH content, the fraction of bridged graft was very close to that of branched graft. This conclusion was somewhat different from the conventional viewpoint, namely, the fraction of bridged graft was always much lower than that of branched graft under any condition. Moreover, the results indicated that the grafting degree increased almost linearly to MAH and DCP concentrations. On the other hand, it was found that the amount of grafted MAH dropped sharply with increasing the length of grafted MAH, indicating that MAH monomers were mainly attached onto the PE chain as single MAH groups or very short oligomers. With respect to the crosslink of PE, the results showed that the fraction of PE‐(MAH)_n‐PE crosslink structure increased continuously, and hence the fraction of PE‐PE crosslink decreased with increasing MAH concentration. Finally, quantitative relationship among number average molecular weight of the PE, MAH, and DCP contents was given. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5714–5724, 2004     

Effect of the initial maleic anhydride content on the grafting of maleic anhydride onto isotactic polypropylene

A series of ¹³C‐enriched maleic anhydride grafted isotactic polypropylene samples were prepared in solution at 170 °C by changes in the initial maleic anhydride content. The NMR spectra of the samples showed that the signals of the maleic anhydride attached to the tertiary carbons of the isotactic polypropylene chains increased considerably with increasing maleic anhydride content, whereas the signals of the maleic anhydride on the radical chain ends (with a single bond) arising from β scission did not. On the other hand, the signals of the maleic anhydride on the radical chain ends with double bonds increased markedly with increasing maleic anhydride content, and this suggested that β scission could occur extensively after maleic anhydride was attached to the tertiary carbons. As a result, the molecular weight of the grafted polypropylene decreased significantly with increasing maleic anhydride content in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5529–5534, 2005     

Grafting of maleic anhydride to hydrocarbons below the ceiling temperature

Maleic anhydride has been grafted to eicosane and squalane at 60–80°C using 1,2-dichlorobenzene as solvent and benzoyl peroxide as initiator. These hydrocarbons are low molecular weight models for hydrocarbon polymers containing secondary and tertiary hydrogen atoms. In the absence of the hydrocarbon and with monomer concentrations of the order of 1M, low molecular weight poly(maleic anhydride) is formed. On addition of the hydrocarbon, the main product is grafted material and very little homopolymer is formed. The grafts consist primarily of single succinic anhydride units but some of them are short poly(maleic anhydride) chains. Ceiling temperature considerations control the formation of homopolymer in the absence of hydrocarbon substrate. In the presence of eicosane or squalane, initiation of grafting proceeds by hydrogen abstraction from the hydrocarbon. The main factor controlling graft length is then the ratio of the rates of intramolecular hydrogen abstraction and of monomer addition to succinic anhydride radicals © 1995 John Wiley & Sons, Inc.     

Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism

In order to elucidate the reaction mechanism of both the radiation-induced and benzoyl peroxide-catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ-ray or ultraviolet-irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one-electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion-radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion-radical are resonance-stabilized. Therefore, the present polymerization may be designated a radical-induced cationic polymerization.     

A kinetic study on grafting of maleic anhydride onto a thermoplastic elastomer

Maleation of a thermoplastic elastomer, styrene-[ethylene-butylene]-styrene (SEBS) triblock copolymer, was carried out by a solution grafting reaction with maleic anhydride initiated by dicumyl peroxide. The reaction products from the graft reaction in xylene, commonly chosen as the solvent for maleation graft reactions, were identified using liquid chromatograph (LC), IR, and ¹³C-NMR. Side products from the graft reaction were identified by the LC analysis and, it was concluded that xylene affected the graft reaction through its active methyl groups. Reaction mechanisms were investigated by performing free radical kinetics analysis. The reaction orders and the apparent rate constant were estimated. It was concluded that a proper choice of the solvent might favor better graft efficiency. © 1993 John Wiley & Sons, Inc.     

Free-radical-induced polymerization of epoxides in the presence of maleic anhydride

The free-radical-induced reactions of cyclohexene oxide in the presence of maleic anhydride have been found to lead to polyether in presence of AIBN and to a mixture of polyether, ester, and maleic anhydride adduct of polyether with di-tert-butyl peroxide (DTBP), the amounts of the mixture components depending on the concentration of DTBP and the temperature. Analogous reactions in the presence of succinic anhydride lead to no polyether. The obtained polyether has no hydroxyl group. The reaction appears to consist of three different steps, radical initiation, cationic propagation, and radical termination.     

Laser-initiated polymerization of epoxies in the presence of maleic anhydride

Laser-initiated polymerization of cyclohexene oxide in the presence of maleic anhydride was investigated. The influences of solvents laser irradiation time and the monomer feed ratio on the polymer yield and composition were evaluated. The rate of polymerization increased with an increase in the molar concentration of maleic anhydride in the monomer feed. Short irradiation times of 1–3 min duration gave very high yield of epoxy polymer (>80% conversion). Infrared spectral studies of the polymer product indicated the formation of polyether linkage at lower levels of conversion and an adduct of polyether and maleic anhydride at higher polymer conversions. The quantitative chemical analyses results also showed similar results. The results indicated that the polymerization was initiated by the excited charge transfer complex between the electron donor, cyclohexane oxide, and the electron acceptor–maleic anhydride. In the initial stages of polymerization, cyclohexene oxide undergoes a cationic polymerization in the presence of the radical anion of maleic anhydride. Laser-initiated polymerization of cyclohexene oxide/maleic anhydride is several hundred times more efficient than UV-initiated polymerization, as measured by the energy absorbed by the polymer system.     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Radical-catalyzed homopolymerization of maleic anhydride in presence of polar organic compounds

Polar organic compounds either (1) inhibit the peroxide-catalyzed bulk homopolymerizations of both MAH and MMA at 80°C, (2) do not inhibit the polymerization of either MAH or MMA, or (3) inhibit the polymerization of MAH but not that of MMA. Compounds generally used as polymerization inhibitors or antioxidants inhibit the polymerizations of both MAH and MMA, presumably by interaction with peroxide decomposition products. Ketones, ethers, acids, esters, nitriles, imides, sulfones, sulfonates, sulfonamides, and acyl disulfides do not inhibit either MAH or MMA polymerization. However, amides, lactams, carbamates, amine oxides, phosphites, phosphates, phosphonates, phosphoramides, phosphine oxides, monosulfides, sulfoxides, aryl disulfides, and thiazyl disulfides inhibit the polymerization of MAH but not that of MMA. Inhibition presumably occurs as a result of electron transfer from the nitrogen-, phosphorous- or sulfur-containing electron donor compound to the MAH carbocation which is an intermediate in the polymerization of MAH.     

Polymerization of methyl methacrylate in a tetrahydrofuran–maleic anhydride system. Part II

A donor–acceptor complex consisting of tetrahydrofuran and maleic anhydride initiates photochemical and thermal polymerization of methyl methacrylate. The mechanism of the transformation of this complex was investigated by studying changes in its electrical conductivity, its chemiluminescence, and various influences on its initiating capability (water, air, DPPH, substitution of styrene for methyl methacrylate and of 1,4-dioxane for tetrahydrofuran). It has been shown that initiation by radicals cannot be clearly excluded and that ionic radicals form in the system and can initiate the anionic growth of the chain.     

Grafting onto wool. II. BPO-initiated grafting of polystyrene

Grafting of polystyrene (PS) onto wool has been carried out in aqueous medium by use of benzoyl peroxide (BPO) as initiator in the presence of an acetic acid–pyridine mixture which acted as a pH modifier. Percent grafting was found to be dependent on concentration of acetic acid and pyridine, concentration of monomer, concentration of BPO, and reaction temperature. The role of pH modifier upon BPO-initiated grafting is established by the observation that no grafting occurred when one of the components of the pH modifier was absent.     

Potentiometric determination of maleic anhydride in the presence of cis-3,6-endomethylene-1,2,3,6-tetrahydrophthalic (endic) anhydride

A procedure is developed for the determination of maleic anhydride in the presence of endic anhydride by potentiometric titration in aqueous-organic solutions. It is found that separate titration of a hydrolyzed mixture of anhydrides is most efficient in the system acetonitrile-water (3 : 2).     

Neodymium oxide‐assisted melt free‐radical grafting of maleic anhydride on isotactic‐polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd₂O₃), ‐assisted melt free‐radical grafting of maleic anhydride (MAH) on isotactic‐polypropylene (i‐PP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd₂O₃ into reactive system leads to an enhancement of the grafting degree of MAH, along with an elevated degradation of i‐PP matrix. When Nd₂O₃ content is 4.5 mmol %, the increment of the grafting degree of MAH (maximally) is up to about 30% compared with that of the related system without adding Nd₂O₃, while the severest degradation of i‐PP matrix simultaneously occurs. On the basis of the reaction mechanism of PP‐g‐MAH proposed before, the sequence of β‐scission and grafting reaction is discussed in detail. It is found that, for the reactive system studied, most tertiary macroradicals first undergo β‐scission, and then, grafting reaction with MAH takes place at the new radical chain ends. The imported Nd₂O₃ has no effect on the aforementioned reaction mechanism, whereas it enhances the initiating efficiency of the initiator, dicumyl peroxide (DCP). We tentatively explain the experimental results by means of synergistic effect between DCP and Nd₂O₃. It is calculated that the synergistic effect is maximal when the molar ratio of DCP to Nd₂O₃ is approximately 1:6. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 134–142, 2006     

Grafting of maleic anhydride on poly(L-lactic acid). Effects on physical and mechanical properties

Maleic Anhydride (MAH) was grafted onto poly(L-lactic acid) (PLLA) in the presence of dicumyl peroxide (DCP) as a radical initiator. The effect of the MAH and DCP concentrations on the grafting and the physical and mechanical properties of PLLA films were investigated. The glass transition temperature and crystallinity significantly decreased with addition of MAH. The thermal decomposition of the PLLA films was affected by the MAH content while the mechanical properties were almost unchanged. A slight increase in molecular weight was found, which could be attributed to either the MAH branching reaction or a possible crosslinking reaction between the PLLA chains increasing the chain entanglements.     

羟基自由基引发的马来酸酐聚合反应机理AM1研究

用AM1方法计算了马来酸酐、羟基自由基及其加成产物α-羟基丁二酸酐基自由基的电子结构、电荷分布和键级.应用前线轨道理论和成键三原则研究了羟基自由基引发下马来酸酐聚合过程中α-羟基丁二酸酐基自由基活性中间体参与反应的可能性及其自由基聚合反应机理.计算结果表明:马来酸酐基态分子的HOMO和LUMO分别对应于双键CC的成键π-MO和反键π -MO;马来酸酐的羟基自由基加成反应活化能计算值为55 7kJ/mol;马来酸酐在羟基自由基引发下的自由基聚合产物是链式结构,与实验事实相符.