Ionic graft copolymerization. III. Graft copolymerization of β-propiolactone onto polyacrylonitrile containing diketene units

Polyacrylonitrile (PAN)–β-propiolactone (βPL) graft copolymer was synthesized by means of the ionic polymerization of βPL in the presence of polyacrylonitrile containing diketene units by using basic catalysts. A graft copolymer was produced by the copolymerization of βPL with the lactone ring in the trunk polymer. In this graft copolymerization method, the grafting efficiency was low. However, grafting efficiency increased with the mole ratio of polymeric lactone to βPL; also higher molecular weight of PβPL favored higher grafting efficiency. The reactivity ratio of polymeric lactone to βPL was estimated to be in the range of 0.1–0.3.     

Ionic graft copolymerization. VII. Ionic graft copolymerization of β-propiolactone onto the trunk polymers containing pyridine,amide, sulfonyl chloride,and carboxylic acid anhydride groups

The graft copolymerization of β-propiolactone (βPL) onto the various trunk polymers containing polar substituents such as pyridine, amide, sulfonyl chloride, and carboxylic acid anhydride groups was carried out. In the grafting onto the basic trunk polymer containing 4-vinylpyriding units, two kinds of grafting mechanism are supposed. In the case of rigorously dried trunk polymer, the polymerization is initiated by betaine and proceeds with higher grafting efficiency. Another is initiated by pyridinium hydroxide and proceeds with lower grafting efficiency. Another is initiated by pyridinium hydroxide and proceeds with lower grafting efficiency in the presence of some amount of water. With acidic trunk polymer containing sulfonyl chloride groups, no graft copolymer was produced. The grafting efficiency of βPL onto the amphoteric trunk polymer containing acrylamide units was found to be between those of basic and acidic trunk polymer. In addition, the grafting by means of ionic copolymerization of βPL with maleic anhydride units contained in trunk polymer proceeded with very high grafting efficiency.     

Ionic graft copolymerization. V. Graft copolymerization of β-propiolactone onto the trunk polymers containing carboxylic acid,sulfonic acid,and other salts

β-Propiolactone (βPL) was graft-copolymerized onto styrene–divinylbenzene copolymers containing various carboxylates or sulfonates, composed of anions and cations having different electronegativities. In parallel, the mechanism of polymerizations of βPL by relatively neutral catalysts was studied in comparison with the behaviors of graft copolymerizations. In the graft copolymerization onto the trunk polymer containing various carboxylates, a lower electronegativity of countercation favors a higher anionic polymerization activity and the order of rate of polymerization coincides with that of anionic activities of catalysts. On the other hand, in the case of trunk polymer containing sulfonates, a higher electronegativity of countercation favors a cationic polymerization activity, and the order of rate of polymerization coincides with that of cationic activity of catalyst. The order of grafting efficiency at fixed total conversion coincides almost with that of anionic activity. The comparatively higher grafting efficiency in the grafting onto trunk polymer containing carboxylic acid might support an anionic graft copolymerization mechanism by carboxyl anion. The two following mechanisms were proposed for the initiation of the polymerization by the trunk polymer containing sodium sulfonate, in which acrylic acid is transformed from βPL.     

Ionic graft copolymerization. VI. Graft copolymerization of β-propiolactone and N-vinylcarbazole onto trunk polymer containing carboxylic acid,sulfonic acid,and their salts

It was pointed out in previous papers that both cationic and anionic polymerization might be involved simultaneously in grafting onto trunk polymers containing ? COOH or ? SO₃Na. The graft copolymerization of β-Propiolactone (βPL)–N-vinylcarbazole (NVCZ) onto styrene-divinylbenzene copolymers containing carboxylic acid, sulfonic acid, and their salts was carried out in order to distinguish between the polymers produced by anionic and cationic mechanisms. The polymer obtained by the polymerization of βPL–NVCZ with BF₃·OEt₂, a typical cationic catalyst, consisted mainly of NVCZ units, but the polymer obtained with BuLi, a typical anionic catalyst, consisted mainly of βPL units. In the graft copolymerization of NVCZ–βPL onto trunk polymer containing ? COOH, the NVCZ contents of the branch polymer and the tolueneinsoluble fraction were estimated to be ca. 50 mole-%; therefore these polymers were produced by both cationic and anionic mechanisms. In the case of graft copolymerization onto the trunk polymer containing SO₃Na, it was found that both cationic and anionic polymerization also occurred simultaneously.     

Ionic graft copolymerization. VIII. Homopolymerization of β-propiolactone by radical catalysts in the presence of electron acceptors and application to graft copolymerization

The polymerization of β-propiolactone (βPL) induced by radiation and by radical catalysts, the influences of radical inhibitors and electron acceptors on this polymerization, and graft copolymerization were studied. It was found that βPL was polymerized by benzoyl peroxide in the presence of electron acceptors such as maleic anhydride and acrylonitrile. This polymerization method was applied to graft copolymerization. The electron donative trunk polymer containing ether groups was heated with benzoyl peroxide or was irradiated by γ-rays from Co⁶⁰ in the presence of maleic anhydride as the electron acceptor. βPL was added subsequently to form the graft copolymer.     

Ionic graft copolymerization. IV. Polymerization of β-propiolactone by acetic acid,p-toluenesulfonic acid,and their sodium salts

Acetic acid, toluenesulfonic acid, and their salts are used as four representative ionic catalysts for polymerization of β-propiolactone (βPL). They are classified as follows: sodium acetate is an anionic catalyst, acetic acid is a neutral one having more covalent character, sodium toluene sulfonate is a neutral one having more ionic character, toluenesulfonic acid is a cationic one. The neutral catalyst having more covalent nature is hardly dissociated, and therefore the rate of polymerization is quite small; however, dissociated ions consist of a higher neucleophilic anion and a higher electrophilic cation. On the contrary, the neutral catalyst having an ionic bond dissociates more easily, but the formed ions consist of the less reactive anion and cation. Therefore, it is of interest whether β-propiolactone is polymerized by a cationic mechanism or an anionic mechanism by these catalysts. The mechanisms of polymerizations of βPL by these neutral catalysts were studied on the basis of the different behaviors of polymerizations by the four catalysts described above. In the cationic polymerization by toluenesulfonic acid, the rate of polymerization was high, but the conversion reaches a low, limited value. In the anionic polymerization by sodium acetate, the rate of polymerization was high and the degree of polymerization of polymer was the highest. Acetic acid has the lowest catalyst activity and the degree of polymerization is also very small. It was found that the polymerization by sodium p-toluenesulfonate was accelerated in the presence of acrylic acid produced from βPL by hydrogen-transfer reaction.     

Ionic graft copolymerization. I. Homopolymerization of β-propiolactone by sodium acetate catalyst

The polymerization of β-propiolactone (βPL) by sodium acetate catalyst has been investigated. The polymerization behavior with monomer purified with calcium chloride was found to be a little different from that previously reported for this monomer. That is, poly-β-propiolactone (PβPL) obtained from βPL dried with CaCl₂ has a higher degree of polymerization than that obtained from conventionally treated βPL, and its infrared spectrum shows type II configuration, which differs from that reported in previous papers. Some chain transfer reaction is observed even for the polymerization of the CaCl₂–dried βPL; however, this is less important in toluene. The electronegativity of the anion or cation in catalyst greatly influences the rate of polymerization.     

Peroxomonosulphate initiated graft copolymerization of o‐toluidine onto nylon 6 and wool fibers—A kinetic approach

Chemical polymerization of o‐toluidine (OT) in the presence of nylon 6 and wool fibers initiated by peroxomonosulphate (PMS) in an aqueous acidic medium was carried out under nitrogen atmosphere. During the polymerization process, graft copolymers were formed along with homopolymers of OT. A procedure is given for the separation of poly(o‐toluidine) (POT) grafted fiber from the homopolymer. Rate of homopolymerization (R_h), rate of grafting (R_g), percentage grafting, and percentage grafting efficiency were determined. Rate constants were evaluated from the experimental results. The chemical grafting of POT onto nylon 6 and wool fibers was confirmed through Fourier transform infrared (FTIR) spectroscopy and electrical conductivity measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2317–2326, 2002     

Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. V. Charge‐transfer complex (1)

In previous studies, the photografting polymerization of vinyl acetate (VAC) and maleic anhydride (MAH) was investigated systematically. After that, to increase the grafting rate and efficiency and make the project more practicable, a VAC–MAH binary monomer system was employed for simultaneous photografting onto the surface of low‐density polyethylene film. The effects of several crucial factors, including the composition and total concentration of the monomer solution and different types of photoinitiators and solvents, on the grafting polymerization were investigated in detail. The conversion percentage (CP), grafting efficiency (GE), and grafting percentage were measured by gravimetry. The results showed that the monomer composition played a big part in this binary system; appropriately increasing the content of MAH in the monomer feed was suited for grafting polymerization. The growth of the total monomer concentration, however, made the copolymerization faster and was unfavorable for grafting polymerization. The three photoinitiators—2,2‐dimethoxy‐2‐phenylacetophenone (Irgacure 651), benzoyl peroxide, and benzophenone (BP)—led to only slight differences in CP, but for GE, BP was the most suitable. As for the different solvents—acetone, ethyl acetate, tetrahydrofuran (THF), and chloroform—using those able to donate electrons (acetone and THF) resulted in relatively higher CPs; on the contrary, the use of the other solvents made GE obviously higher, and this should be attributed to the charge‐transfer complex (CTC) that formed in this system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 903–909, 2005     

Grafting mechanism in SBR–St–MMA core–shell emulsion copolymerization

The graft copolymerization of styrene and methyl methacrylate on SBR latex particles in the core–shell emulsion process was conducted in a 600 mL glass stirred vessel with the BPO? Fe²⁺ redox initiator. The effects of the principal factors such as the polymerization temperature, monomer-to-polymer ratio, the frequency of monomer addition and conversion on the grafting degree, and the grafting efficiency were studied. The surface-controlled process model was proposed to describe the grafting mechanism. © 1994 John Wiley & Sons, Inc.     

Graft copolymerization of p‐acryloyloxybenzoic acid and p‐methacryloyloxybenzoic acid onto isotactic polypropylene and their thermal properties: Part I

The polymerization and grafting of the monomers p‐acryloyloxybenzoic acid and p‐methacryloyloxybenzoic acid were studied. Poly(acryloyloxybenzoic acid) was obtained by γ‐radiation‐induced solution polymerization and bulk melt polymerization initiated by dicumyl peroxide. Poly(methacryloyloxybenzoic acid) could be obtained only by bulk melt polymerization. The graft copolymerization of the monomers onto isotactic polypropylene was carried out in bulk. The maximum grafting was reached in shorter times at higher temperatures, and it also increased with the concentration of the monomers in the reaction medium. The thermal and crystallization behavior of the graft copolymers was studied with differential scanning calorimetry and wide‐angle X‐ray diffraction. The graft copolymerization of p‐acryloyloxybenzoic acid did not have any influence on the formation of both α forms (monoclinic) of polypropylene, whereas p‐methacryloyloxybenzoic acid led to the α₂ form. The β‐crystalline modification (hexagonal) formed in poly(acryloyloxybenzoic acid)‐g‐polypropylene products at 185°C and at higher grafting temperatures and also in the second run of differential scanning calorimetry studies after fast cooling. The β form was not observed in graft copolymers of poly(methacryloyloxybenzoic acid). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

强酸弱碱型两性离子交换纤维的制备I.苯乙烯和4-乙烯基吡啶的接枝共聚

采用聚丙烯纤维为原料 ,研究了预辐照接枝苯乙烯 (St)和 4 -乙烯基吡啶 (4 - VP)的接枝共聚规律。选择合适的接枝工艺条件 ,总接枝率可达 30 0 %～ 70 0 %。通过改变 St和 4 - VP单体的投料比或采用分批投料方式还可以改变两种官能团的比例和系列结构。经进一步磺化 ,可制得两性离子交换纤维。     

Graft copolymerization of glass fiber and its application

Modified glass fibers, containing unsaturated hydrocarbon surface groups, were prepared by a hydrothermal treatment, with allylglycidylether in excess as reagent. Graft polymerization of the treated glass fiber with styrene and methylmethacrylate was carried out in sealed tubes, under nitrogen, using benzoyl peroxide (BPO) and cumene hydroperoxide (CHPO) as initiators. When BPO was used as the initiator, the grafting efficiency was extremely low, but the graft copolymerization behavior was similar to that of usual organic polymers. With CHPO, both grafting ratio and grafting efficiency were very high. Various properties of composite materials containing grafted glass cloth were studied. Flexural strength, flexural modulus, and interlaminar shear strength increased proportionally to the increase of the grafting ratio; the same values were decreased only in a small extent after the boiling test.     

Graft copolymerization of acrylonitrile onto Cassia tora gum with ceric ammonium nitrate–nitric acid as a redox initiator

The graft copolymerization of acrylonitrile (AN) onto Cassia tora gum (CTG) was carried out in an aqueous medium with a ceric ammonium nitrate (CAN)–nitric acid initiation system. The percentage grafting and percentage grafting efficiency were determined as functions of the concentrations of CAN, nitric acid, AN, and CTG and the polymerization temperature and time. The results are discussed, and a reaction mechanism is proposed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 129–136, 2003     

聚乙二醇接枝聚醋酸乙烯酯的聚合动力学研究

以过氧-2-乙基己酸叔丁酯为引发剂,进行了聚乙二醇(PEG)存在下的醋酸乙烯酯(VAc)本体接枝聚合,考察了各VAc:PEG配比下聚合速率、PEG上PVAc的接枝率、PVAc的接枝效率、PEG的被接枝效率以及接枝共聚物的分子量随聚合时间的变化规律.结果发现,随配方中VAc配比的增加,聚合速率与极限转化率明显增加,聚合反应出现明显的自动加速现象;当VAc:PEG配比较大时,综合速率参数K随聚合时间不断上升,当VAc:PEG配比较低时,K随聚合时间呈下降趋势.各VAc:PEG配比下PVAc的接枝率几乎都随转化率的增大而线性地增加,接枝效率则几乎不随聚合时间而变;接枝率的大小正比于VAc:PEG配比,接枝效率则普遍较高,低VAc:PEG配比时,接枝效率可达95%以上;PEG的被接枝效率虽随转化率和VAc:PEG配比的增加而明显增加,但总体仍较低,表明聚合体系中有相当多一部分PEG未被接枝.高的VAc接枝效率和低的PEG被接枝效率表明,该Graft From接枝聚合体系中,可能存在着Graft Onto的接枝聚合机理.根据定义用来计算PEG-g-PVAc的数均分子量,发现随聚合转化率的增大而减小,并逐渐趋于常数,配方中VAc浓度越大越大;由GPC测试、PVAc普适校正计算发现,接枝聚合产物的分子量分布指数在1.5～2.5 之间,且随单体浓度和转化率的增加而增大.这些均与聚合体系的凝胶效应有关.     

引发剂体系对AN-MAA本体共聚合的影响

以聚合热力学为基础,研究了引发剂体系对丙烯腈(AN)-甲基丙烯酸(MAA)本体共聚合的影响.不同活性的偶氯二异丁腈(AIBN)和偶氮二异庚腈(ABVN)单独引发AN-MAA共聚合时,不能消除暴聚现象.采用AIBN/ABVN复合引发剂且复合引发剂半衰期为63,4～117.1 h、总用量为0.12～0.24 phr、聚合温...     

Photochemical reactions of high polymers. XIII. Photografting of methyl methacrylate onto the polymers bearing thiosulfate groups

Polymers bearing pendent thiosulfate groups, that is, sodium poly(vinyl benzyl thiosulfate) (PVBB) and the sodium salt of poly(vinyl hydrothiosulfatoacetate)(PV AcB), were prepared. The photograft polymerization of methyl methacrylate onto these polymers was carried out. The relationships between irradiation time and conversion, degree of grafting, and grafting efficiency were investigated in the photograft polymerization. It was ascertained that the pendent thiosulfate groups acted as effective initiators for the graft polymerization. From the number of endgroups in the homopolymer formed along with the graft polymer, the mechanism of the graft polymerization was discussed and it was verified that the graft polymerization was initiated by the thiyl radical formed by scission of the sulfur–sulfur bond of the pendent thiosulfate group. An unusually high degree of grafting and extremely rapid polymerization rate observed in the graft polymerization suggested the dual functions of thiosulfate-bearing polymer as initiator and emulsifier. It was found that addition of FeCl₂ to this polymerization system increased the rate of polymerization and the degree of grafting but decreased the grafting efficiency. The effect of FeCl₂ was interpreted by assumption of a photo-redox reaction between thiosulfate group and Fe²⁺.     

Graft copolymerization of vinyl monomers onto modified cottons. VIII. Dimethylaniline–benzyl chloride-induced grafting of methyl methacrylate onto partially carboxymethylated cotton

The feasibility of dimethylaniline (DMA)–benzyl chloride (BC) mixture to initiate graft polymerization of methyl methacrylate (MMA) onto partially carboxymethylated cotton was examined. The graft yield depends on the nature of the solvent used along with water; ethanol proved to be the best at a water;ethanol ratio of 90:10. Considerable grafting occurred in the presence of acetic acid at a concentration of 200 mmol/l. Higher concentrations of this acid decrease grafting significantly. The graft yield obtained in the presence of formic acid was much lower than that obtained in the presence of acetic acid. Inclusion of hydrochloric or sulfuric acid in the graft polymerization system prevent grafting. A DMA–BC mixture at a concentration of 0.08:0.087 mole/l. constitutes the optimal concentration for grafting. This contrasts with 0.32:0.35 mole/l. for total conversion. The rate of grafting increases by raising the polymerization temperature; it follows the order 50°>60°>65°>70°>75°C. Furthermore, increasing the monomer concentration caused a significant enhancement in the graft yield and total conversion.     

Study of radiation‐induced graft copolymerization of butyl acrylate onto chitosan in acetic acid aqueous solution

The graft copolymerization of butyl acrylate onto chitosan in acetic acid aqueous solution was investigated, using the γ‐ray of ⁶⁰Co γ‐irradiation method. Fourier transform infrared spectra analysis, X‐ray diffraction analysis, and scanning electron microscopy characterized the graft copolymer. The effect of synthesis variables in the graft copolymerization have been discussed in the light of grafting efficiency, grafting percentage, and homopolymer percentage. Hydrophilicity and impact strength of the films formed from copolymer solution were tested and their feasibility as seed coating was studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2855–2860, 2003     

Graft copolymerization onto Tamarind Kernel Powder: Ceric(IV)‐initiated graft copolymerization of acrylonitrile

Tamarind Kernel Powder (TKP) is derived from the seeds of Tamarindus indica Linn., a common and most important tree of India. It is extensively used in cotton sizing, as a wet‐end additive in the paper industry, as a thickening, stabilizing, and gelling agent in the food industry. However, because of its fast biodegradability there is a need to prepare graft copolymers of TKP. The graft copolymerization of acrylonitrile (AN) onto TKP with ceric ammonium nitrate as a redox initiator in an aqueous medium has been studied. The reaction conditions were optimized to afford maximum percent grafting and percentage grafting efficiency of AN onto TKP, which was found to be 86% and 64%, respectively. Fourier Transform Infrared Spectrum of the grafted products showed an additional sharp absorption band at 2244 cm^?1 due to ? C?N stretching, thereby confirming the grafting of AN onto TKP. Scanning electron microscopy studies indicated change in contour of the polysaccharide on grafting and the thick polymeric coating of AN on the surface alongwith grafting of AN such that all the gap between polysaccharide particles have been closed. Thermal studies using thermogravimetric and differential gravimetric analyses confirmed that TKP‐g‐AN has overall high thermal stability than pure TKP. Reaction mechanism of grafting of acrylnitrile onto TKP is also proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009