Acrylic acid polymerization kinetics

The kinetics of the isothermal polymerization of acrylic acid were determined utilizing ¹H-NMR spectroscopy. The polymerization rate was observed to depend approximately on the $ \frac{3}{2} $ power of monomer and the $ \frac{1}{2} $ power of sodium persulfate concentration. This is consistent with a model in which the rate of initiation is itself dependent on the monomer concentration. The polymerization rate was also observed to have a strong dependence on percent neutralization, decreasing with increasing level of neutralization up to 75 to 100% neutralization, and then increasing again. The activation energy for the rate of polymerization was between 9 and 13 kcal/mol except for 100% neutralized acrylic acid, which had an activation energy of 18 kcal/mol. These data suggest that a transition in mechanism occurred at 100% neutralization. Increasing the ionic strength by the addition of sodium chloride also increased the rate. The dependence of the molecular weight on the above variables was also quantified for use in the model. It decreased with increasing conversion, decreasing ionic strength and increasing initiator. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2029–2047, 1997     

The State of NaOH in NaOH/Poly(Sodium Acrylate) Composite

NaOH/poly(sodium acrylate) composites were prepared by in situ polymerization of acrylic acid with an overneutralization level by adding excess NaOH. The composites were studied by XRD, IR and ²³Na MAS NMR spectroscopy. The results showed that the high neutralization degree (>100%) may lead to a complete polymerization. Both XRD and ²³Na MAS NMR spectra did not show any peaks of phase-separated NaOH or Na₂CO₃ until the neutralization degree was up to 217.5%. It can be presumed that the aggregates of Na⁺ ions can contain approximately two Na⁺ units for every carboxyl group before the phase separation.     

辉光放电电解等离子体引发合成聚丙烯酸钠/腐植酸复合高吸水性树脂

以丙烯酸和腐植酸为原料,N,N-亚甲基双丙烯酰胺为交联剂,在水溶液中采用辉光放电电解等离子体引发聚合反应制备聚丙烯酸钠/腐植酸复合高吸水性树脂。 考察了放电电压、交联剂、丙烯酸中和度、后聚合温度、腐植酸钠和丙烯酸的含量对树脂吸水率的影响,讨论了树脂在0.9%氯化钠溶液中的溶胀速率和不同pH值溶液中的溶胀行为。 用红外光谱和热重分析分别对产物进行了结构表征和稳定性测试,结果表明,最佳的合成条件为：放电电压470 V、交联剂质量分数为0.6%、腐植酸钠质量分数为4%、丙烯酸质量分数为10%、中和度60%、后聚合温度70 ℃。 所得复合树脂对蒸馏水的吸水率为1152 g/g,对0.9%NaCl溶液的吸水率为89 g/g,800 ℃后复合树脂残留率为44.3%。     

Emulsion polymerization of styrene using an alkali-soluble random copolymer as polymeric emulsifier

An alkali-soluble random copolymer (ASR), poly(styrene/α-methylstyrene/acrylic acid), was used as a polymeric emulsifier in the emulsion polymerization of styrene. The calorimetric technique was applied to study the kinetics of emulsion polymerization of styrene using ASR and a conventional ionic emulsifier, sodium dodecyl benzenesulfonate (SDBS). ASR could form aggregates like micelles, and the solubilization ability of the aggregates was dependent on the neutralization degree of ASR. The rate of polymerization in the ASR system was lower than that in the SDBS system. This result can be explained by the creation of a hairy ASR layer around the particle surface, which decreases the diffusion rate of free radicals through this region. Although a decrease in particle size was observed, the rate of polymerization decreased with increasing ASR concentration. The higher the concentration of ASR is, the thicker and denser ASR layer may be, and the more difficult it would therefore be for radicals to reach the particle through this layer of ASR. The rate of polymerization decreased with increasing the neutralization degree of ASR. The aggregates with high neutralization of ASR are less efficient in solubilizing the monomer and capturing initiator radicals than that of the lower neutralization degree, which leads to decrease in rate of polymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2865–2872, 1998     

粉煤灰复合聚丙烯酸钠凝胶的制备及其溶胀性能

粉煤灰(CFA)存在的情况下,采用自由基溶液聚合法,以过硫酸钾(KPS)为引发剂,N,N'-亚甲基双丙烯酰胺(NNMBA)为交联剂,制备了粉煤灰复合聚丙烯酸钠凝胶(CFAPAANa)。 以丙烯酸单体质量为基准,当交联剂用量为0.08%,引发剂用量为0.4%,粉煤灰用量为3%,丙烯酸中和度为70%,聚合温度为70 ℃时,所合成的粉煤灰复合聚丙烯酸钠凝胶在蒸馏水和生理盐水中平衡溶胀比最高,分别为1556(g/g)和168(g/g)。 考察了复合凝胶在不同介质溶液中的溶胀动力学,保水性能以及在土壤中的降解行为。 溶胀动力学研究表明,蒸馏水中溶胀初期复合凝胶聚合物链段的扩散运动能够调控凝胶溶胀的快慢及程度,而生理盐水中水分子的平移和对流运动在凝胶的溶胀过程中起着关键性作用。 保水和降解实验结果表明,25 ℃时,50 h凝胶保水率为64%,土壤中50 d时降解率达60%。 相比于聚丙烯酸钠凝胶,粉煤灰复合凝胶保水率提高了8%。     

Preparation and properties of diatomite composite superabsorbent

A novel diatomite composite superabsorbent was synthesized by solution polymerization of partially neutralized acrylic acid and diatomite, using N,N′-methylenebisacrylamide as a crosslinking agent and hydrogen peroxide and L -ascorbic acid as a redox initial system. The influences of some reaction conditions, such as diatomite content, neutralization degree of acrylic acid, amount of initiator, amount of crosslinking agent, monomer concentration, and the reaction temperature on swelling characteristic were investigated. The water absorbency of the sample prepared at optimum conditions was 99 g/g in 0.9 wt% NaCl solution. The results of swelling rate measurement showed that diatomite composite superabsorbent had better swelling rate than that of poly(sodium acrylate) prepared in the same conditions. Other properties, i.e. water retention, reswelling ability and resistance to salt, were also examined. Copyright © 2007 John Wiley & Sons, Ltd.     

Research on various factors influencing the moisture absorption property of sodium polyacrylate

Sodium polyacrylate was synthesized with acrylic acid as the monomer, and sodium bisulfate and ammonium persulfate as the initiator, by means of aqueous solution polymerization. The factors influencing the properties of moisture absorption, such as monomer concentration, dosage of initiator, and reaction temperature were systematically investigated. The experimental results indicate that the moisture-absorbing property of this polymer was better than other traditional material, such as silica gel, and molecular sieve. The best reaction condition and formula are based on the orthogonal experiment design. The optimum moisture absorbency of sodium polyacrylate reaches 1.01 g/g. The mathematical correlation of this polymer with various factors and moisture absorbency is obtained based on the multiple regression analysis. The moisture content intuitive analysis table shows that neutralization degree has the most significant influence on moisture absorbency, followed by monomer concentration and reaction temperature, while other factors have less influence. Supported by the 863 Project (Grant No. 2005AA001650)     

Synthesis of Acrylic Acid／Kaoline Powder Superabsorbent Composite by Inverse-suspending Polymerization

An acrylic acid/kaoline powder superabsorbent composite with a water absorbency of the superabsorbentcomposite about 1/800 was synthesized by inverse-suspending polymerization reaction between acrylic acidmonomer and kaoline ultrafine powder. The influence of the dispersant agent on the configuration of theproducts in the inverse suspension polymerization is investigated. The influences of the kaoline powder.cross-linker, initiator, neutralization degree and the volume ratio of oil to water phase on the water absorben-cy of the superabsorbent composites are discussed in the paper.     

丙烯酸与海藻酸钠共聚制备耐盐性高吸水树脂

丙烯酸与海藻酸钠共聚制备耐盐性高吸水树脂     

Synthesis,characterization and water absorbency properties of poly(acrylic acid)/sodium humate superabsorbent composite

A novel poly(acrylic acid)/sodium humate superabsorbent composite was synthesized by aqueous solution polymerization of acrylic acid using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of sodium humate. The effects on water absorbency such as initial monomer concentration, degree of neutralization of acrylic acid, amount of crosslinker, initiator and sodium humate, etc. were investigated. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with a sodium humate content of 20% exhibited an absorption of 1268 g H₂O/g sample and 93 g H₂O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. Swelling rate and water retention tests were also carried out. The results show that sodium humate, as a kind of functional filler, can enhance comprehensive properties of superabsorbent composite and reduce the product cost significantly. Copyright © 2005 John Wiley & Sons, Ltd.     

Photopolymerization kinetics of tributylmethylammonium‐based (meth)acrylate ionic liquids and the effect of water

Polymerizable ionic liquids were synthesized from the neutralization reaction between tributylmethylammonium hydroxide and methacrylic or acrylic acid, and their photopolymerization kinetics have been determined. The acrylate monomer polymerization rate exhibited a profound dependence on the water content as follows: the monomer viscosity was a strong function of the water content, increasing substantially as the water content increased from less than 5 to 30%. For the tributylmethylammonium acrylate with less than 5% water, the viscosity was 2000 times greater than that of butyl acrylate. The high viscosity is proposed to reduce both the propagation and termination steps. Both monomers exhibited an increase in rate with temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3766–3773, 2008     

壳聚糖-聚丙烯酸复合水凝胶的药物控制释放行为

以壳聚糖(Cs)和丙烯酸(AA)为原料,利用自由基聚合法制备了具有孔洞结构的复合水凝胶Cs-PAA,并研究了AA的量、交联剂的量、聚合温度和AA的中和度对水凝胶溶胀度的影响以及复合水凝胶对烟酸的控制释放。 结果表明,Cs-PAA复合水凝胶具有良好的pH值、离子强度敏感性,且溶胀度最高达1228 g/g,其在pH=686的缓冲溶液中的烟酸累积释放率明显大于其在pH=1.80的缓冲溶液,因此Cs-PAA水凝胶可作为肠口服药物的载体。     

Synthesis of Poly(methyl acrylate) Grafted onto Silica Particles by Z-supported RAFT Polymerization

RAFT polymerization of methyl acrylate (MA) mediated by silica-supported 3-(methoxycarbonyl-phenyl-methylsulfanylthiocarbonylsulfanyl) propionic acid (Si- MPPA) and 3-(benzylsulfanylthiocarbonylsulfanyl) propionic acid (Si-BSPA) was investigated. The molecular weight and polydispersity of grafted polymeric chains and the grafted chain transfer agent (CTA) efficiency (G_e) were strongly dependent on the types and loading of Si-CTAs and free CTA used in solution. Under similar reaction conditions, the graft polymerization mediated by Si-MPPA was better controlled than that using Si-BSPA. The introduction of a free CTA in solution during Si-MPPA mediated polymerization could significantly decrease the polydispersity of free and grafted polymeric chains and enhance the grafted CTA efficiency, and longer polymeric chains could be grafted onto silica support when Si-MPPA with a higher CTA loading was used to mediate the polymerization. In all cases, the RAFT polymerization using 2-(2-cyanopropyl) dithiobenzoate (CPDB) as a free CTA could afford well-defined grafted PMA and significantly increased G_e value, while the polymerization rate was also decreased.     

Low‐Temperature,Rapid Copolymerization of Acrylic Acid and Sodium Acrylate in Water

Regulating the aqueous polymerization of acrylic acid (AA) is a major opportunity for future materials design, requiring the development of scalable, industry‐oriented procedures that afford modest molar mass and dispersity control without long reaction times and environmentally demanding conditions. To address these challenges, this report presents the rapid copolymerization of aqueous mixtures of AA and sodium acrylate using an inexpensive and scalable protocol based on alkyl iodides/sodium iodide as mediators in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1414–1419     

Unexpected end‐groups of poly(acrylic acid) prepared by RAFT polymerization

Low‐molecular‐weight poly(acrylic acid) (PAA) was synthesized by reversible addition fragmentation chain transfer polymerization with a trithiocarbonate as chain‐transfer agent (CTA). With a combination of NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, the PAA end‐groups of the polymer were analyzed before and after neutralization by sodium hydroxide. The polymer prior to neutralization is made up of the expected trithiocarbonate chain‐ends and of the H‐terminated chains issued from a reaction of transfer to solvent. After neutralization, the trithiocarbonates are transformed into thiols, disulfides, thiolactones, and additional H‐terminated chains. By quantifying the different end‐groups, it was possible to demonstrate that fragmentation is the rate limiting step in the transfer reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5439–5462, 2004     

Semi-Continuous Heterophase Polymerization to Synthesize Nanocomposites of Poly(acrylic acid)-Functionalized Carbon Nanotubes

Two materials, pure poly(acrylic acid) (PAA) and nanocomposites with a matrix of PAA and carbon nanotubes (CNTs) as reinforcing agent were synthesized by semi-continuous heterophase polymerization (SHP). CNTs were prepared by a chemical vapor deposition technique and purified by steam. CNTs were characterized by a high resolution scanning electron microscopy (HRSEM) and Raman and Fourier transform infrared spectroscopies. Nanocomposites were prepared with: (i) purified CNTs (CNTs_p) or (ii) purified and functionalized CNTs possessing an acyl chloride moiety (CNTs_OCl). In both cases, the nanocomposites synthesis was carried out by in situ polymerization of acrylic acid (AA) by SHP. When CNTs_OCl were used previously to the polymerization of AA, a series of specific amounts of CNTs_OCl and AA were mixed to induce a chemical reaction between the carboxyl group of AA and the acyl chloride group of the CNTs_OCl. The product, acrylic acid grafted to CNTs_OCl (CNTs_OCl-AA), was used to prepare the PAA-CNTs_OCl nanocomposites. The PAA-CNTs_OCl nanocomposites were characterized by HRSEM, Raman, FTIR and CPMAS ¹³C-NMR spectroscopies and also by thermogravimetric analysis (TGA). The results reveal that PAA-CNTs_OCl nanocomposites were formed by PAA macromolecules grafted to CNTs_OCl. The kinetic behavior observed for the synthesis of pure PAA or PAA-CNTs_OCl nanocomposites by SHP was similar. Latexes of PAA-CNTs_OCl nanocomposites were stable without formation of a precipitate of CNTs_OCl for over 1.5 years, while latex prepared with CNTs_p and PAA, was unstable and formation of a precipitate of CNTs_p was observed immediately after its preparation. PAA-CNTs_p nanocomposites were characterized only by TGA. Moreover, latex of the PAA-CNTs_p nanocomposite that did not precipitate immediately after its preparation, turned into a gel; this gelation never occurred with the PAA-CNTs_OCl nanocomposite latex.     

Ring-Opening Polymerization of L-Lactide in Supercritical Chlorodifluoromethane

The ring-opening polymerization of L -lactide initiated by 1-dodecanol/stannous 2-ethylhexanoate (DoOH/Sn(Oct)₂) was carried out in supercritical chlorodifluoromethane at various reaction times, pressures, and temperatures. The monomer conversion increased to ca 70 % on increasing the reaction time to 25 h. The molecular weight of the product also increased to ca 75,000 g/mol over the same period. Increasing the pressure resulted in an accelerated polymerization rate. The pressure-induced increase in the rate of L -LA polymerization can be explained by the formation of chemical bonds in the transition state, which implies the production of a transition state with a lower partial molar volume than the reactants.     

Synthesis of polyimide and poly(imide-benzoxazole) in polyphosphoric acid

A polyimide made from 4,4′-diaminodiphenyl ether (ODA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was synthesized in polyphosphoric acid. Although the polymerization proceeded heterogeneously, a polyimide with an inherent viscosity of 0.90 was obtained, and a tough and flexible film was made from this polyimide. This polymerization was a one-step reaction including polycondensation and imidization; this was also confirmed by a model reaction between aniline and phthalic anhydride. Utilizing this polymerization method, 3,3′-dihydroxy-4,4′-diaminobiphenyl and 2 mol of 4-aminobenzoic acid were reacted in PPA, then BPDA was reacted to obtain an alternate copolymer containing imide and oxazole rings. This reaction gave a homogeneous solution of the poly(imide-benzoxazole). © 1993 John Wiley & Sons, Inc.     

丙烯酸与丙烯酰胺共聚制备高吸水性树脂

采用溶液聚合法,以N,N’-亚甲基双丙烯酰胺（NMBA）为交联剂,过硫酸钾（KPS）为引发剂合成了高吸水性树脂聚（丙烯酸-丙烯酰胺）（P（AA—AM））,研究了单体配比、丙烯酸中和度、引发剂及交联剂用量、反应温度对树脂在去离子水和0．9％盐水中吸水率的影响．最佳条件下制备的树脂在去离子水中吸水率为750g·g^-1,在0．9％盐水中吸水率为85g·g^-1．     

表面交联的三元共聚高吸水树脂的合成及其性能研究

以丙烯酸、丙烯酰胺及丙烯磺酸钠为单体,采用水溶液聚合法制得三元共聚高吸水树脂(SAP1),用乙二醇二环氧甘油醚与氯化铝作交联剂,对SAP1进行表面交联处理得高吸水树脂SAP2。SAP2在加压下吸盐水率高,凝胶颗粒表面干爽且易分散。考察了引发温度、丙烯酸中和度、交联剂、引发剂、丙烯酰胺及丙烯磺酸钠的用量对常压下吸盐水率的影响。同时还考察了乙二醇二环氧甘油醚与无机盐用量对常压及加压下吸盐水率的影响。