Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. VI. Charge‐transfer complex (2)

The photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (E_a) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent E_a's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), E_a's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, E_a's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, E_a's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005     

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     

Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. IV. Maleic anhydride

In general, it has been accepted that maleic anhydride (MAH) cannot be homopolymerized under normal conditions. However, MAH can be grafted onto substrates under UV irradiation rather easily. In this study, the photografting polymerization of MAH was examined with low‐density polyethylene (LDPE) film as a substrate. The initiating performances of different photoinitiators, including benzophenone (BP), Irgacure 651, and benzoyl peroxide (BPO), were examined. The effects of some principal factors, such as the temperature, solvent, and UV intensity, on the grafting polymerization of MAH were also investigated. The results show that MAH can be smoothly grafted onto LDPE film by UV radiation. Enhancing the intensity of UV radiation and elevating the irradiation temperature facilitate the grafting polymerization of MAH. Among BP, Irgacure 651, and BPO, Irgacure 651 can initiate the polymerization of more MAH, but BP is more effective for the initiation of surface grafting polymerization. Solvents of MAH also have a great influence on the grafting polymerization; some of them even seem to take part in the reaction. The occurrence of photografting polymerization was verified with Fourier transform infrared and electron spectroscopy for chemical analysis spectra. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2318–2325, 2003     

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride,and their charge transfer complex. I. VAc(1)

Photografting of vinyl acetate (VAc) onto LDPE films was carried out with lamination technology and simultaneous method, using BP as photoinitiator. Some principal factors affecting the grafting polymerization were investigated in detail. The experimental results showed that oxygen dissolved in monomer solution had great influence on grafting polymerization. Compared with other routine monomers (St, MMA, AN, AA, and AAm), VAc exhibited higher photografting reactivity. It was observed that the reaction temperature affected the graft polymerization markedly. To film samples with a given diameter, there exists optimum thickness of monomer solution. Adding a pertinent amount of water to the photografting polymerization system could accelerate the polymerization. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1513–1521, 2000     

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride (MAH), and their charge transfer complex (CTC). III. VAc(3)

Vinyl acetate (VAc) was grafted onto low‐density polyethylene (LDPE) substrates by UV irradiation with benzophenone (BP) as the photoinitiator. BP preabsorbed film samples and BP precoated film samples were prepared in advance and applied as the substrates onto which VAc was photografted, together with the method in which BP was dissolved in VAc directly. In addition, the efficiency of the polymerizations applying the preirradiation technology was examined. The conversion percent, grafting percent, and grafting efficiency were determined by a gravimetric method. The contact angles of the grafted films against water were also measured. The results show that BP preabsorbing and precoating were favorable to grafting polymerization, especially the BP precoating method, which was due to its simple operation and the ease of controlling the amount of BP. The diffusion of BP and VAc through the substrates proved to be an important factor for grafting polymerization. Through UV irradiation, dormant groups can be introduced onto LDPE film, which may be activated again by UV irradiation or by heating, leading to the formation of free radicals. Grafting polymerization can be initiated during the activation process in the presence of monomer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1426–1433, 2001     

Bulk grafting of poly(styrene‐alt‐maleic anhydride) onto preirradiated polyolefin membranes in supercritical carbon dioxide

To take advantage of the property of supercritical carbon dioxide as both a solvent and swelling agent, the bulk grafting of poly(styrene‐alt‐maleic anhydride) [P(MAH‐alt‐St)] onto preirradiated polyolefin membranes was performed by a combination of γ‐ray‐preirradiation‐induced graft copolymerization and supercritical fluid‐swollen polymerization. The trapped radicals on the polyolefin backbones were uniformly distributed by γ‐ray irradiation under a nitrogen atmosphere. Subsequently, these polymeric trapped radicals initiated the alternating copolymerization of styrene (St) and maleic anhydride (MAH) infused into the swollen polymer matrix with the aid of supercritical CO₂. It was important that the graft copolymers were relatively pure without any contaminants, including homopolymers, monomers, and initiators. The experimental results show that the degree of grafting could be easily controlled. In addition, St/MAH could synergistically promote the bulk grafting process and strongly effect on the alternating trend; this was confirmed by element analysis and differential scanning calorimetry. Soxhlet extraction, X‐ray diffraction, and Fourier transform infrared spectroscopy indicated that the P(MAH‐alt‐St) was covalently bonded to the polymeric backbones. Scanning electron microscopy showed that the alternating graft chains were uniformly dispersed throughout the 5‐mm thickness of the polymer membranes on the nanometer scale. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modified chitosan. I. Optimized cerium ammonium nitrate‐induced synthesis of chitosan‐graft‐polyacrylonitrile

Chitin was extracted from shrimp shells and then deacetylated to obtain chitosan. The degree of deacetylation of the chitosan was determined to be 0.76 using pH‐metric titration. A large number of cyanide functional groups were introduced onto chitosan by grafting with polyacrylonitrile as an efficient way of modification. The graft copolymerization reactions were carried out under argon atmosphere in a homogeneous aqueous phase (containing a small portion of acetic acid) by using ceric ammonium nitrate as an initiator. Evidence of grafting was obtained by comparing FTIR spectra of chitosan and the graft copolymer as well as solubility characteristics of the products. The synthetic conditions were systematically optimized through studying the influential factors, including temperature and concentrations of the initiator, acrylonitrile monomer (AN), acetic acid, and chitosan. The effect of individual factors was investigated by calculating and monitoring the variations of the grafting parameters [i.e., grafting ratio (Gr), grafting efficiency (Ge), add‐on value (Ad), homopolymer content (Hp), and total conversion (Ct)]. Under optimum conditions, the grafting parameters were achieved as 535, 98, 81, 2, and 102%, respectively. A mechanism for the free‐radical grafting was proposed. As empirical rates of polymerization and graft copolymerization were plotted against [AN] and [Ce⁴⁺]^1/2, the experimental kinetic data displayed a good match to a reported rate statement. The overall activation energy for the graft copolymerization was determined to be 44.9 kJ/mol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2048–2054, 2003     

Surface modification of low‐density polyethylene films by UV‐induced graft copolymerization with a fluorescent monomer

Surface modification of argon plasma–pretreated low‐density polyethylene (LDPE) film via UV‐induced graft copolymerization with a fluorescent monomer, (pyrenyl)methyl methacrylate (Py)MMA, was carried out. The chemical composition and morphology of the (Py)MMA‐graft‐copolymerized LDPE [(Py)MMA‐g‐LDPE] surfaces were characterized, respectively, by X‐ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM). The concentration of the surface‐grafted (Py)MMA polymer increased with Ar plasma pretreatment time and UV graft copolymerization time. The photophysical properties of the (Py)MMA‐g‐LDPE surfaces were measured by fluorescence spectroscopy. After graft copolymerization with the fluorescent monomer, the surface of the LDPE film was found to have incorporated new and unique functionalities. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1526–1534, 2001     

聚乙烯的微波辐射溶液接枝反应的研究

研究了微波辐射下,以过氧化二苯甲酰（BPO）为引发剂,以二甲苯为溶剂,低密度聚乙烯（LDPE）与马来酸酐（MAH）的溶液接枝共聚反应,考察了反应条件对产物接枝率的影响,得到了接枝率（以MAH计）为63mmol/100g的马来酸化聚乙烯（LDPE-g-MAH).通过红外光谱及DSC等方法对产物的测试以及同条件下微波枝与常规热接枝的对照实验得出结论,微波辐射接枝可以得到较高接枝率的马来酸化聚乙烯。     

等离子体引发丙烯酸在LDPE薄膜表面接枝聚合的研究（Ⅰ）

利用等离子体引发接枝技术对低密度聚乙烯（LDPE）薄膜进行表面改性处理,通过对接枝单体后LDPE薄膜表面单体接枝率的计算和表面接触角以及表面自由能的测量,系统地研究了反应气体、放电功率、处理时间、处理压力对等离子体引发接枝反应的影响,并利用红外光谱、扫描电镜对接枝单体后薄膜的表面化学组成及表面结构进行了表征分析。     

Radiation‐induced graft copolymerization of α‐methyl styrene and butyl acrylate mixture into polyetheretherketone films

Radiation‐induced graft copolymerization of α‐methyl styrene (AMS), butyl acrylate (BA) monomers, and their mixture was investigated on poly(etheretherketone) films. The graft polymerization was carried out using ethyl methyl ketone as the medium for the copolymerization and the maximum degree of grafting of 27% was achieved. It was observed that the grafting is significantly influenced by the reaction conditions, such as reaction time, preirrradiation dose, monomer concentration, monomer ratio, and the reaction temperature. The degree of grafting increases as the monomer concentration increases up to 30%, beyond which a decrease in the grafting was observed. The degree of grafting showed a maximum at 40% BA content in the monomer mixture. The temperature dependence of the grafting process shows decreasing grafting with the increase in the reaction temperature. The presence of AMS and BA grafts in the film was confirmed by FTIR spectra. The relative change in the PBA/PAMS fraction with respect to the reaction temperature has been found in this study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Kinetics of atom transfer radical polymerization of crosslinkable terpolymer P(MMA‐BA‐HEMA)

A crosslinkable terpolymer P(MMA‐BA‐HEMA) was prepared by atom transfer radical copolymerization of 2‐hydroxyethyl methacrylate, methyl methacrylate and butyl acrylate. The structure of the terpolymer was characterized by ¹H NMR and gel permeation chromatography. The effects on the polymerization of ligand, initiator, solvent, CuCl₂ added in the initial stage and reaction temperature were investigated. The optimal reaction conditions were ethyl 2‐bromopropionate as initiator, CuCl/PMDETA as catalyst, cyclohexanone as solvent, catalyst/ligand = 1:1.5, [M]₀:[I]₀ = 200:1 and temperature 70 °C. The reaction followed first‐order kinetics with respect to monomer concentration, indicating the best control over the polymerization process, a constant concentration of the propagating radical during the polymerization, efficient control over M_n of the polymer and low polydispersity (M_w/M_n < 1.3). © 2013 Society of Chemical Industry     

Atom transfer radical copolymerization of methyl methacrylate with N‐cyclohexylmaleimide

Atom transfer radical polymerization has been applied to simultaneously copolymerize methyl methacrylate (MMA) and N‐cyclohexylmaleimide (NCMI). Molecular weight behaviour and kinetic study on the copolymerization with the CuBr/bipyridine(bpy) catalyst system in anisole indicate that MMA/NCMI copolymerization behaves in a ‘living’ fashion. The influence of several factors, such as temperature, solvent, initiator and monomer ratio, on the copolymerization were investigated. Copolymerization of MMA and NCMI in the presence of CuBr/bpy using cyclohexanone as a solvent instead of anisole displayed poor control. The monomer reactivity ratios were evaluated as r_NCMI = 0.26 and r_MMA=1.35. The glass transition temperature of the resulting copolymer increases with increasing NCMI concentration. The thermal stability of plexiglass could be improved through copolymerization with NCMI. © 2000 Society of Chemical Industry     

Melt grafting of maleic anhydride onto polypropylene with 1‐decene as a second monomer

The influence of 1‐decene as the second monomer on the melt‐grafting behavior of maleic anhydride (MAH) onto polypropylene (PP) was studied with differential scanning calorimetry and Fourier transform infrared spectroscopy. We found that the value of the grafting degree increased from 0.68% for pure MAH‐g‐PP to 1.43% for the system with a 1‐decene/MAH molar ratio of 0.3, whereas the maximum value with styrene (St) as the second monomer was 0.98% under an St/MAH molar ratio of 1.0. Compared with the contribution of St/MAH‐g‐PP to the peeling strength between the PP and polyamide (PA) layer for a PP/PA laminated film, the introduction of 1‐decene/MAH‐g‐PP increased the peeling strength from 180 g/15 mm to 250 g/15 mm. 1‐Decene inhibited the chain scission behavior of PP. 1‐Decene reacted with MAH to form a 1‐decene/MAH copolymer or the Alder‐ene reaction product before the two monomers grafted onto PP. The grafting of the reactive product onto PP greatly improved the grafting degree of MAH. What is more, because of the similar chemical structures of 1‐decene and PP, the affinity of 1‐decene with PP was higher than that of St. Compared with St, the introduction of less 1‐decene led to a higher grafting degree and higher peeling strength. Therefore, we concluded that 1‐decene was more effective for improving the grafting degree of MAH onto PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reactive extrusion for the synthesis of nylon 12 and maleated low‐density polyethylene blends via the anionic ring‐opening polymerization of lauryllactam

Nylon 12 was successfully synthesized in a twin‐screw extruder via the anionic ring‐opening polymerization of lauryllactam (LL). Maleated low‐density polyethylene (LDPE–MAH) was added to improve the mechanical properties of nylon 12. The in situ blends of nylon 12 and LDPE–MAH were characterized by mechanical testing and scanning electron microscopy. With increasing LDPE–MAH content, the tensile strength and flexural strength decreased, whereas the blend had improved impact strength and achieved supertoughness when the content of LDPE–MAH was 30 wt %. In the in situ formed low‐density polyethylene‐g‐PA12 copolymer, the domain of the LDPE–MAH phase was finely dispersed in the nylon 12 matrix. The good interface between the two phases demonstrated that LDPE–MAH could be used as a macromolecular activator to induce the polymerization of LL. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

LDPE熔融接枝MAH及其增容PA6/LDPE合金的研究

以过氧化二异丙苯(DCP)为引发剂,马来酸酐(MAH)为接枝单体,采用熔融法制备了MAH接枝低密度聚乙烯(LDPE-g-MAH)。研究了不同DCP和MAH配比对接枝反应的影响,并以相对接枝率较高的LDPE-g-MAH作为增容剂,讨论了其用量对尼龙6(PA6)/LDPE合金力学性能的影响。结果表明:LDPE/DCP/MAH质量比为100/0.2/2时,相对接枝率较高,该种配方的接枝物可显著改善PA6/LDPE体系的相容性,在PA6/LDPE(质量比50/50)和PA6/LDPE(质量比80/20)两种体系中,增容剂的最佳用量分别为4~5 phr和2~3 phr。     

E/VAC与马来酸酐反应挤出接枝的研究

用同向双螺杆挤出机进行Ｅ／ＶＡＣ熔融接枝ＭＡＨ的反应。考察了单体、引发剂用量和加工条件对接枝率及熔体流动速率的影响。结果表明,在Ｅ／ＶＡＣ接枝ＭＡＨ的反应中,接枝率随着ＤＣＰ用量、ＭＡＨ用量以及螺杆转速的增加出现峰值,较佳的实验配方为Ｅ／ＶＡＣ：ＭＡＨ：ＤＣＰ＝１００：２：０．２。接枝反应对Ｅ／ＶＡＣ的流动性有很大影响,接枝物的熔体流动速率随ＤＣＰ用量的增加而下降。     

(E/VAC)-g-MAH对PP/PBT共混体系的增容改性

以过氧化苯甲酰(BPO)为引发剂,通过熔融接枝法在Brabender转矩流变仪中制得马来酸酐接枝(乙烯/乙酸乙烯酯)共聚物[(E/VAC)-g-MAH]。将该接枝物用于增容聚丙烯/聚对苯二甲酸丁二酯(PP/PBT)共混体系。结果表明,在(E/VAC)-g-MAH的作用下,PP/PBT共混物的力学性能得到提高,界面形貌得到改善,体系的相容性得到明显增强。     

溶剂热法制备AS接枝马来酸酐的研究

以马来酸酐(MAH)为单体、苯乙烯(St)为共单体、过氧化二异丙苯(DCP)为引发剂,采用溶剂热法分别制备了苯乙烯-丙烯腈共聚物(AS)接枝物AS-g-MAH以及AS-g-(MAH-St).利用红外光谱对接枝物进行了结构表征,证明MAH已经成功接枝在AS链上.并用反式滴定法测定了接枝率,讨论了引发剂用量、马来酸酐用量、反应温度、反应时间、反应物浓度和共单体用量对接枝率的影响.结果表明:随着引发剂用量的增加和反应时间的延长,接枝率先增大,然后趋于平稳;随着马来酸酐用量、反应温度和反应物浓度的增加,接枝率先增大后下降;共单体苯乙烯的加入对接枝率的提高有很大的促进作用.     

Hyperbranched copolymers of p‐(chloromethyl)styrene and N‐cyclohexylmaleimide synthesized by atom transfer radical polymerization

The hyperbranched copolymers were obtained by the atom transfer radical copolymerization of p‐(chloromethyl)styrene (CMS) with N‐cyclohexylmaleimide (NCMI) catalyzed by CuCl/2,2′‐bipyridine (bpy) in cyclohexanone (C₆H₁₀O) or anisole (PhOCH₃) with CMS as the inimer. The influences of several factors, such as temperature, solvent, the concentration of CuCl and bpy, and monomer ratio, on the copolymerization were subsequently investigated. The apparent enthalpy of activation for the overall copolymerization was measured to be 37.2 kJ/mol. The fractional orders obtained in the copolymerization were approximately 0.843 and 0.447 for [CuCl]₀ and [bpy]₀, respectively. The monomer reactivity ratios were evaluated to be r_NCMI = 0.107 and r_CMS = 0.136. The glass transition temperature of the resultant hyperbranched copolymer increases with increasing f_NCMI, which indicates that the heat resistance of the copolymer has been improved by increasing NCMI. The prepared hyperbranched CMS/NCMI copolymers were used as macroinitiators for the solution polymerization of styrene to yield star‐shaped poly(CMS‐co‐NCMI)/polystyrene block copolymers by atom transfer radical polymerization. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1992–1997, 2000