Superabsorbent hydrogel of acrylic acid/potassium acrylate copolymers by ultraviolet photopolymerization: Synthesis and properties

Synthesis of superabsorbent hydrogel (SAHG) of acrylic acid‐potassium acrylate copolymer by direct Ultraviolet (UV) photopolymerization is a new method. The effects of degree of neutralization of acrylic acid (AA), photoinitiators, crosslinking agents, and exposure time of UV light on water absorbent properties were investigated. The results showed that the water absorbency (Q) and the salt solution (NaCl, 0.9%) absorbency (Qs) of SAHG, based on Irgacure 651, are high, reaching about 1400 and 130 mL/g, respectively. UV absorption spectrum proved that peak of UV absorption of Irgacure 651 matched the UV light source we used. Among the crosslinking agents, N,N′‐methylene bisacrylamide is more efficient than others, because of its very small content and high Q. ¹³C NMR spectrometry was used to identify the mechanism of crosslinking reaction through esterification of hydroxyethyl acrylate (HEA) and 2‐hydroxypropyl acrylate (HPA) with carboxylic acid group in acrylic acid‐ammonium acrylate copolymerization, but efficiency of crosslinking reaction by esterification was lower than that of copolymerization of vinyl group in crosslinking agent. The Q of acrylic acid‐potassium acrylate copolymer of SAHG reaches 1592 mL/g under the following conditions: degree of neutralization of acrylic acid is 80%, content of Irgacure 651 is 0.25 wt %, content of HEA is 0.2 wt %, and exposure time is 10 min. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1181–1187, 2006     

Synthesis of superabsorbent resin by ultraviolet photopolymerization

Synthesis of superabsorbent resin (SAR) was achieved by a new method, that of direct UV photopolymerization, and in particular the synthesis of a SAR of acrylic acid–potassium acrylate copolymer by UV photopolymerization was investigated. Influences of ratio (mol) of acrylate monomer to acrylic acid monomer, photoinitiators, crosslinking agents, and exposure time of UV light on the water‐absorbent properties were investigated. The results showed that the water absorbency (Q) of SAR based on Irgacure 1700 or Irgacure 1800 was 545–530 mL/g, but under the same conditions Q was 450 mL/g for the SAR based on Irgacure 651. N,N′‐Methylene bisacrylamide, hydroethyl acrylate, and glycerol were used as crosslinking agents, of which N,N′‐methylene bisacrylamide was the most effective. It crosslinked the molecular chains through attending the copolymerization with acrylic acid (AA) and potassium acrylate. When the exposure time was 5 min, the value of Q was 1368 mL/g (the content of N,N′‐methylene bisacrylamide was 100 ppm). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1618–1624, 2004     

Superabsorbent resin of acrylic acid/ammonium acrylate copolymers synthesized by ultraviolet photopolymerization

A new method of synthesizing a superabsorbent resin (SAR) from an acrylic acid/ammonium acrylate copolymer by direct UV photopolymerization was studied. The effects of the degree of neutralization of acrylic acid, the photoinitiators, the crosslinking agents, and the UV‐light exposure time on the water absorbency (Q) were investigated. The results showed that Q of an SAR based on Irgacure 1700 or Irgacure 1800 and Irgacure 651 was high, reaching about 1200 mL/g, but under the same conditions, Q was low for an SAR based on other photoinitiators. The UV absorption spectrum proved that the photoinitiators matched the UV light source. Among the crosslinking agents, N,N′‐methylene bisacrylamide was more efficient than the others at a small concentration and a high value of Q. ¹³C‐NMR spectrometry was used to identify the mechanism of the crosslinking reaction through the esterification of hydroxyethyl acrylate (HEA) and 2‐hydroxypropyl acrylate with carboxylic acid group in acrylic acid/ammonium acrylate copolymerization, but the efficiency of the crosslinking reaction by esterification was lower than that of the copolymerization of vinyl groups in the crosslinking agent. Q of the acrylic acid/ammonium acrylate copolymer for the SAR reached 1255 mL/g under certain conditions (degree of neutralization of acrylic acid = 75%, Irgacure 651 concentration = 0.2 wt %, [HEA] = 0.2 wt %, exposure time = 10 min). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 546–555, 2005     

异氰酸酯改性环氧丙烯酸酯的合成及其光固化动力学的研究

采用两步法合成了可紫外光固化的异氰酸酯改性的环氧丙烯酸酯树脂,并利用元素分析、傅里叶变换红外光谱、核磁共振氢谱对此树脂的结构进行了表征。对树脂及其固化后涂膜的性能测试表明,合成的树脂具有较低的黏度,为4500mPa-s/60℃,固化膜柔韧性能优,低于3mm。采用红外光谱法对此改性树脂的光固化动力学行为进行了分析,结果表明:光引发剂Irgacure1000作为Darocur1173和Irgacure184以质量比1:1构成的复合型光引发剂,比单一的光引发剂具有更优异的引发效果;随着光引发剂Irgacure1000用量的增加,树脂体系光固化反应的聚合速率和树脂中双键的最终转化率都明显增加,但当其用量超过树脂质量的3%时,光固化反应速率和双键的最终转化率又趋于下降;活性单体对树脂光固化行为的影响为:单体的官能度越低、活性单体的用量越大,越有利于树脂的光固化,固化速率和双键的最终转化率都明显提高;此外,增大入射光的光照射强度也有利于树脂的光固化。     

Kinetic study on the UV‐induced photopolymerization of epoxy acrylate/TiO2 nanocomposites by FTIR spectroscopy

The kinetics of the photopolymerization of epoxy acrylate/TiO₂ nanocomposites, with 2′2‐dimethoxy‐1,2‐diphenylethan‐1‐one (Irgacure 651) or benzophenone/N‐methyl diethanolamine as photoinitiators, were studied by FTIR spectroscopy. It was found that nanocomposites had a decreasing photopolymerization rates in comparison with pure epoxy acrylate. The photopolymerization rate of the nanocomposite could also be influenced by initiator types, oxygen, film thickness, irradiation intensity, dispersing media of TiO₂ slurry, and so forth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3281–3287, 2006     

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     

Photopolymerization of N,N‐dimethylaminoethylmethacrylate studied by photocalorimetry

Photopolymerization of dimethylaminoethylmethacrylate (DMAEMA) is studied in bulk and in solutions in the presence of different photoinitiators using differential photocalorimetry (DPC). The rate of DMAEMA photopolymerization is slow compared to that of alkylmethacrylates. Bimodal DPC curves of DMAEMA photopolymerization in bulk are obtained. The type I photoinitiators (IRGACURE® 651 and IRGACURE® 1700), which produce free radicals by homolytic fragmentation of photoexcited molecules, are more effective in promoting photopolymerization of DMAEMA. The type II photoinitiators (benzophenone and IRGACURE® 500), which initiate DMAEMA photopolymerization through an H‐abstraction mechanism involving an amino group from the monomer (polymer), are less efficient and favor the formation of partly crosslinked products. The effects of the photoinitiator concentration, temperature, and solvent on the kinetic data are evaluated and discussed. A scheme of photopolymerization of DMAEMA, including the formation of intermediate DMAEMA based macromonomers, is proposed. The main point of the suggested scheme is a high chain transfer to the DMAEMA monomer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 579–588, 2002     

Synthesis of 4-Methacryloylmethyldiphenylsulphone and its Copolymerization

This paper presents the synthesis of two new compounds: 4-chloromethylphenylsulphone (4-CmDPhSu) and 4-methacryloylmethylphenylsulphone (4-McMDPhSu) which are derivatives of diphenylsuphone. Introduction of the methacryloyl group into 4-CmDPhSu transferred this compound into the vinyl monomer 4-McMDPhSu. This monomer was polymerized and copolymerized with the use of two types of initiators: a mixture containing benzoyl peroxide (BP) and N,N-dimethylaniline (DMA), as well as the photoinitiators Irgacure 651 or Darocur 1173. In further studies, its copolymers with methyl methacrylate were used. Their thermomechanical properties were studied.     

Synthesis and characterization of hyperbranched photosensitive polysiloxane urethane acrylate

A novel hyperbranched photosensitive polysiloxane urethane acrylate (HBPSUA) based on hyperbranched polyesters (HBP-OH) has been synthesized. HBP-OH was synthesized from N,N-diethylol-3-amine methylpropionate as AB₂ monomer and trimethylolpropane (TMP) as a core molecule. The structure of the oligomer was characterized by FTIR, GPC and ¹H NMR. The molecular weight of the oligomer is about 10,000 and the viscosity is 4446 cps at room temperature. The HBPSUA possesses good compatibility with most of acrylate monomers. The effect of photoinitiators, monomers and light intensity on the photopolymerization kinetics of the oligomer HBPSUA was investigated by real-time infrared spectroscopy (RT-IR). The results show that HBPSUA can well photopolymerize under UV-irradiation in the presence of photoinitiators. Irgacure 1700 showed the highest initiating efficiency among those tested photoinitiators. The optimal concentration of photoinitiator (Darocur 1173) is determined as 0.05 wt.%. The system of HBPSUA/TPGDA has the high conversion of double bond and polymerization rate, and they are 92.38% and 22.25 s⁻¹, respectively. Compared with linear systems (PSUA), HBPSUA has the higher photopolymerization rate and lower viscosity. The cured film of HBPSUA possesses good flexibility.     

UV curable coatings for improved gas barrier properties of poly(ethylene terephthalate)

A new high-barrier coating based on methyl (α-hydroxymethyl)acrylate (MHMA) for poly(ethylene terephthalate) (PET) was developed along with the process for preform dipping and cure prior to blow molding into bottles. The UV curable coating gives excellent gas barrier improvement when coated onto PET biaxially oriented thin films. Blown bottle side walls from coated PET preforms also show 2–3 times improvement over uncoated side walls. The effect of photoinitiator concentration, initiator types, and temperature on photopolymerization kinetics of MHMA was investigated. Once the photoinitiator, Irgacure 819^®, concentration became larger than 1 mol%, a decrease in rate of propagation was observed. The conversion also decreased with higher initiator concentration. Irgacure 819^® reduced the auto-acceleration peak and reached maximum rates of polymerization much faster than Irgacure 651^®. It also gave a slightly higher conversion. Overall conversion for combinations of these photoinitiators was high, above 80%. Real-time FTIR (RT-FTIR) studies of copolymerization of MHMA and methyl methacrylate (MMA) showed that conversion was fairly high up to 25 mol% MMA. However, once MMA feed ratio exceeded 10 mol%, a decrease in barrier performance was observed.     

Photopolymerization synthesis of poly(N-isopropylacrylamide) hydrogels

Poly(N-isopropylacrylamide) (NIPAAm) gels were formed by photopolymerization of NIPAAm in the absence of a crosslinker using a water solvent at 25°C. Factors affecting formation were the wavelength region of irradiated light, the type of photoinitiators, and the concentrations of the photoinitiator and monomer. A high-pressure mercury lamp (400 W) was used as a light source. An NIPAAm concentration of 10 wt % and irradiation time of 15 h was used for the photopolymerization. The gel (68% yield) was formed when the quartz glass system was used, but no gelation was observed for the Pyrex glass system that transmits light with π > 290 nm. The gel (100% yield) was easily formed, even in the latter system, when 30 mmol/L of hydrogen peroxide and potassium persulfate were used as the photoinitiator. Water soluble photoinitiators such as ferric chloride and sodium anthraquinone-2,7-disulfonate were not effective for the gel formation. Yield of the gel increased with increasing the potassium persulfate concentration (1–30 mmol/L), but it decreased when a high concentration of hydrogen peroxide (60 mmol/L) was used. The gel yield increased with the NIPAAm concentration (5–20 wt %). The degree of swelling of the resultant poly(NIPAAm) gels, which was measured by immersing the gels in water at various temperatures (0–50°C) for 24 h, steeply decreased at about 30°C with increasing temperature, exhibiting a temperature-responsive character. The gels swelled and shrank in water below and above the temperature, respectively. The extent of the character depended on the concentrations of hydrogen peroxide and monomer. The formation mechanism of the gel in the photopolymerization of NIPAAm using hydrogen peroxide photoinitiator was discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1313–1318, 1997     

Polymer networks with antibacterial activity by UV photopolymerization

The crosslinking by radical UV photopolymerization of mixtures of acrylic oligomers added with 2,4,4′‐trichloro‐2′‐hydroxydiphenyl ether (TCDPE) allows to obtain polymer films which perform like hygienic coatings. The release of the bioactive compound from two types of acrylic networks obtained by UV crosslinking of polyfunctional monomers, namely, epoxy‐based and urethane‐based diacrylic oligomers, has been investigated. The photopolymerization process was influenced by biocide presence only at high biocide concentration, where the plasticizing effect of the biocide increased the double bond conversion. The kinetic curve of the photopolymerization was fitted by an Avrami‐like equation and the release of TCDPE from the networks into solutions of ethanol–water of different compositions was discussed on the base of the Fick's diffusion equation. The antimicrobial activity of the UV photopolymerized film has been tested by putting the coatings in contact with two types of colony‐forming bacteria, the Escherichia coli (Gram negative) and the Staphylococcus aureus (Gram positive). Strong hygienic performances toward the tested pathogens were observed for the urethane and epoxy films containing TCDPE in quantities as low as 0.1 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of novel macrophotoinitiator for the photopolymerization of acrylate

A new kind of macrophotoinitiator (MPI) was synthesized through the copolymerization of acrylic monomers and the polymerizable photoinitiator monomer 2959‐AA. Monomer 2959‐AA was obtained by an esterification reaction between acrylic acid (AA) and the water‐soluble photoinitiator Irgacure 2959 [2‐hydroxy‐4‐(2‐hydroxyethoxy)‐2‐methylpropiophenone]. By adjusting the monomer proportions in the MPIs, two series of MPIs with different 2959‐AA contents and different glass transition temperatures were obtained. The molecular structure of 2959‐AA was characterized by Fourier‐transform infrared spectroscopy, nuclear magnetic spectrometry, and mass spectrometry. Polymerization of 1, 6‐hexanediol diacrylate was initiated using Irgacure 2959 and 2959‐AA, and two series of MPIs to be polymerized were studied with a photo‐DSC test. Results showed that 2959‐AA had higher chemical reactivity than Irgacure 2959 because of the higher solubility of the former. It was evident from the experiments that 2959‐AA content in the MPI progressively increased the polymerization rate and monomer conversion when the glass transition temperatures of MPIs were similar. At the same 2959‐AA content, the polymerization rate slightly slowed down with increased glass transition temperature. However, the radical lifetime and polymerization time were prolonged. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40352.     

紫外光引发聚(丙烯酸-丙烯酰胺)/膨润土高吸水性复合材料的制备研究

以N,N-亚甲基双丙烯酰胺(MBAM)为交联剂,Irgacure184为光引发剂,采用紫外光引发聚合的方法制备了聚(丙烯酸-丙烯酰胺)/膨润土高吸水性复合材料。研究了膨润土用量、光引发剂、交联剂、中和度等因素对吸水性能的影响,并用红外吸收光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)的方法表征了复合材料的结构和形态。     

Thin film solvent‐free photopolymerization of n‐butyl acrylate. I. Static film studies

The results are presented for a detailed investigation involving the free‐radical photopolymerization of n‐butyl acrylate in the form of thin static films. The aim of this work is to benchmark the performance of a novel thin film spinning disk reactor that may be used for the continuous production of linear polymers using photoinitiation. Industrially relevant film thicknesses (200 μm to 1 mm) are studied as opposed to earlier work that looked into extremely thin films (5–25 μm). Such extreme film thicknesses will be difficult to sustain in a thin film reactor without adversely affecting the wettability of the reaction surface and the uniformity of the film. The effects of four main variables (film thickness, UV intensity, initiator concentration, and exposure time) are studied under static film conditions. A 366‐nm wavelength is utilized for the UV radiation with 2,2‐dimethoxy‐2‐phenylacetophenone (Irgacure 651) as the photoinitiator dissolved in n‐butyl acrylate. The molecular weights, polydispersities, and monomer conversions are measured by gel permeation chromatography. In a 400 μm thick film, conversions of >90% can be achieved with an exposure time of 40 s at a radiation intensity of 175 mW/cm². The results using the same polymerization system in the spinning disk reactor are presented and compared with the static film results in Part II of this series. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2079–2095, 2004     

不同高吸水性树脂吸附金属离子的研究

本文共制备两种吸水树脂:一种以丙烯酸(AA)为单体,采用过硫酸钾(KSP),硝酸铈铵(CAN)为复合引发剂,N-N′-亚甲基双丙烯酰胺(MBA)为交联剂,加入羧甲基纤维素(CMC)接枝共聚制备纤维素类吸水树脂;另一种则用相同浓度的单体,引发剂,交联剂,反应条件下制备聚丙烯酸类吸水树脂。通过对两种吸水树脂吸附重金属离子如Na+、Li+、Ca2+、Zn2+、Co2+、Fe3+溶液,以及对尿素的吸附能力,吸水速率,保水能力的测试比较,结果表明:在相同的反应条件下纤维素类吸水树脂对离子的吸附能力强于聚丙烯酸类吸水树脂。     

Electro‐optic properties of CO2 fixed‐polymer/nematic LC composite films

Bis(cyclic carbonate) was obtained from the epoxide and CO₂ reaction with a quaternary ammonium halide salt catalyst. Cyclic carbonate derivatives were then reacted with amine to obtain quantitatively poly(hydroxy)urethanes that were reacted with isophorone diisocyanate (IPDI) and end capped with acrylate to form prepolymers. These prepolymers were mixed with reactive diluents and nematic LCs, and subjected to UV cure to form polymer/LC composite films in a transparent cell. Three types of diglycidyl ether [poly(propyleneglycol), cyclohexane, bisphenol A], three types of end‐capping acrylates [2‐hydroxyethyl acrylate (HEA), 2‐hydroxypropyl acrylate (HPA), and 2‐hydroxyethyl methacrylate (HEMA)], three types of multyfunctional diluents [tripropylene glycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA), dipentaerythritol hydroxy penta/hexa acrylate (DPHPA)], and three types of photoinitiators (Irgacure‐651, Irgacure‐184, Darocure‐1173) were incorporated to control the morphology, and hence, the electro‐optic properties of the polymer/nematic LC composite films. Poly(propylene glycol) diglycidyl ether segment of polyurethane acrylate (PUA) showed lower viscosity and gave larger domain size resulting in lower threshold (V₁₀) and driving (V₉₀) voltages, together with larger nematic–isotropic transition temperature depression. HEA end‐capped PUA gave larger polymer–LC phase separation and smaller V₁₀ as well as V₉₀. TPGDA‐based PUA showed the lowest V₁₀ and V₉₀ and the shortest response time. Among the three types of photoinitiators used Irgacure‐651 showed the larger LC domain, and smaller V₁₀ and V₉₀. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2744–2753, 2001     

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     

P(AA/AM/APEG)/纳米二氧化硅复合高吸水树脂的合成及性能

以丙烯酸(AA)、丙烯酰胺(AM)、烯丙基聚氧乙烯醚(APEG)为单体,再引入纳米二氧化硅(nano-SiO_2),以过硫酸铵为引发剂,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了P(AA/AM/APEG)/纳米二氧化硅有机/无机复合高吸水性树脂,考察了交联剂加量、引发剂加量、纳米二氧化硅加量对树脂吸水倍率的影响,并用红外光谱和扫描电镜对产物进行了表征。结果表明:合成最佳条件加入纳米二氧化硅能提高树脂的吸水性能,粒径在80~120目时,复合树脂吸水倍率达到1 865 g/g,P(AA/AM/APEG)树脂吸水倍率为1 681g/g;温度在20~60℃时,复合吸水树脂吸水倍率变化幅度不大;pH在6~8时,其吸水性能最好,吸水倍率为1 865~1 444 g/g;此外,复合树脂具有较好的保水性能,树脂常温下保存15 d,其保水率达到83.2%。红外光谱和扫描电镜分析表明,纳米二氧化硅成功接枝到聚合物上并形成海绵状结构。     

Photopolymerization of powder suspensions for shaping ceramics

The photopolymerization of suspensions of ceramic powders in monomer solutions is the fundamental step for forming techniques where a liquid suspension is solidified with UV light. The photopolymerization behavior is determined by the properties of the monomer and photoinitiator and by the transport of photons in the suspension. Photon transport in suspensions involves scattering from the particle and absorption by photoinitiators and inert dyes. The photopolymerization behavior is related to the formulation of the suspensions. Proper formulations are discussed for several applications. Techniques for characterization include cure depth measurements, photocalorimetry, and photorheology.