Temperature‐, pH‐, and ion‐stimulus‐responsive swelling behaviors of poly(dimethylaminoethyl methacrylate) gel containing cholic acid

Poly(dimethylaminoethyl methacrylate) hydrogels containing cholic acid (PDMAEMA–CA) were synthesized by radiation crosslinking. The introduction of 10 and 20 mol% cholic acid (CA) into the poly(dimethylaminoethyl methacrylate) (PDMAEMA) hydrogel decreased the maximum swelling ratio (SR) of the gel from 40 to 6 and 5, respectively. The incorporation of CA with dimethylaminoethyl methacrylate led to a decrease in the lower critical swelling temperature of the gel from 44 to 42°C but did not exert big influence on the ion‐stimulus‐responsive properties of the gel. However, the pH sensitivity of the PDMAEMA–CA gel was quite different from that of PDMAEMA gel. The SR of PDMAEMA gel decreased at pH 2.5, whereas the SRs of the PDMAEMA–CA gels showed a convex‐upward function of pH; that is, SR of the PDMAEMA–10% CA gel first increased (pH 1.2–3.2) and then decreased (pH 3.2–11.9) with increasing pH. The pH‐stimulus‐responsive swelling behavior of the PDMAEMA–20% CA gel was similar to that of the PDMAEMA–10% CA gel except for the unique swelling behavior exhibited in the lower pH region. The unique decrease in SR in strong acidic solutions was attributed to aggregations driven by the hydrophobic interactions between CA molecules. Phase separation of the gel in strongly acidic solutions was observed; that is, the margin of the swollen gel was transparent and elastic (cellular structure), whereas the core of it was opaque (aggregated structure) as recorded by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39998.     

Rapid pH‐dependent phase transition and elasticity of stimuli‐responsive cationic poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with a dimethacrylate crosslinker

Stimuli‐responsive hydrogels prepared from poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) and its copolymers have attracted much interest to serve in biomedical and pharmaceutical applications. To investigate pH‐dependent swelling and elasticity, a series of cationic hydrogels based on N,N‐dimethylaminoethyl methacrylate were prepared by free radical crosslinking copolymerization at 60 °C in the presence of tetraethylene glycol dimethacrylate as the crosslinker. The equilibrium swelling and the mechanical properties of the PDMAEMA hydrogels were investigated as a function of the gel preparation concentration. To explain the effect of pH on the equilibrium swelling of the hydrogels, pH‐dependent swelling studies were carried out in solutions of pH ranging from 2.1 to 10.7. It was found that the PDMAEMA hydrogels exhibit a rapid pH‐dependent phase transition in aqueous solutions; that is, the gels first remain in the swollen state at acidic pH then collapse in a very narrow range of pH. The results showed that the volume of PDMAEMA hydrogels in acidic conditions is about 10‐ to 40‐fold larger than that in the basic pH region. By using the Flory–Rehner theory, the characteristic network parameters of the PDMAEMA hydrogels were calculated and good agreement obtained between the swelling equilibria of hydrogels and their mechanical properties over the whole range of gel preparation concentration. © 2012 Society of Chemical Industry     

Swelling behavior of amphiphilic gels based on hydrophobically modified dimethylaminoethyl methacrylate

The amphiphilic gels based on hydrophobically modified dimethylaminoethyl methacrylate with different 1-bromoalkanes (1-C_nH_2n+1Br, n = 2, 4, 6, 8, 12) were synthesized by radiation-induced polymerization and crosslinking. The length of alkyl side chains had significant influence on the swelling behavior of the resulting gels. The swelling degree of the gels decreased with the increase of side chain length, and the gel hardly swelled when n = 12. The effect of temperature and ionic strength on the swelling behavior of the resulting gels revealed that (1) the gels with longer side chains (n ≥ 8) had upper critical solution temperature, while other gels were not thermo-sensitive. (2) Antipolyelectrolyte effect was observed when immersing the gels (n ≥ 8) in NaCl solutions in certain concentration range. The dramatic difference in swelling behavior was attributed to the different gel structures. The gels with short side chains (n ≤ 6) had cellular structure of normal polyelectrolyte gels. The gels (n ≥ 8) had an aggregation gel structure caused by the hydrophobic interaction among alkyl groups and the formation of ion-cluster between tetra-alkyl ammonium cation and Br⁻, which had been analyzed with the aid of SEM, Br⁻-selective electrode and fluorescence molecular probe.     

pH-responsive swelling behavior,elasticity and molecular characteristics of poly(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylaminoethyl methacrylate) gels at various initial monomer concentrations

The equilibrium swelling degree and the modulus of elasticity of pH-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) gels prepared at various initial monomer concentrations were investigated both in buffer solutions and in aqueous salt solutions. As pH of the solution is increased, PDMAEMA gels first remain in the swollen state up to pH 7.7, then exhibit pH-sensitive phase transitions at 8.0 in which PDMAEMA gels attain a collapsed state. The swelling kinetic measurements of PDMAEMA gels showed that pH sensitivity of PDMAEMA is quite stable and the swelling process is reproducible in accordance with pH changing. The swelling behavior of PDMAEMA gels was analyzed by Flory-Rehner theory and the results were combined by the results of compression measurements to calculate the molecular characteristics of gels. The resulting pH-responsive PDMAEMA gels were elastic and displayed good swelling behavior both in buffer solutions and in aqueous salt solutions, therefore, they can be used as a kind of carrying material in drug delivery systems.     

pH‐sensitive dimethylaminoethyl methacrylate (DMAEMA)/acrylamide (AAm) hydrogels: Synthesis and adsorption from uranyl acetate solutions

A random copolymer of dimethylaminoethyl methacrylate (DMAEMA) and acrylamide(AAm) [poly(DMAEMA/AAm)], with a pH‐sensitive character, was prepared by a redox polymerization method. Increasing the DMAEMA content of the gel, the pH, and the ionic strength of the solution decreased the swelling ratios of the hydrogels. The adsorption of poly(DMAEMA/AAm) hydrogels from uranyl acetate (UA) solutions was studied at different pHs. The adsorption capacity of hydrogels increased from 200 to 1200 mg of UA per gram of dry hydrogel with increasing pH of the adsorption solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2028–2031, 2003     

Preparation of stimuli‐responsive nanogels of poly [2‐(dimethylamino) ethyl methacrylate] by heterophase and microemulsion polymerization using gamma radiation

Poly [2‐(dimethylamino) ethyl methacrylate], PDMAEMA, was synthesized by heterophase polymerization at 70°C using sodium dodecylsulfate (SDS) as stabilizer and potassium persulfate (KPS) as the initiator. Conversions were 60%, polymer content 18%, and intensity average particle diameter, D_p, 32 nm. γ‐rays irradiation of PDMAEMA nanolatexes and DMAEMA/H₂O/SDS microemulsions using ethyleneglycol dimethacrylate produced nanogels responding to temperature and pH. Nanogels shrinked as temperature increased, swelled excessively in acidic solutions (maximum D_p: 498 nm) and deswelled (minimum D_p: 257 nm) in basic solutions for the case of the nanogels obtained from PDMAEMA nanolatexes. pH response to swelling is due to protonation of amine groups in the backbone of PDMAEMA in acidic conditions leading to electrostatic interactions in the nanogel. POLYM. ENG. SCI., 54:1625–1631, 2014. © 2013 Society of Plastics Engineers     

Cationic brush‐like terpolymer with pH responsive thickening behavior in a surfactant system

A new kind of cationic brush‐like terpolymer was synthesized by copper(I)‐mediated atom transfer radical polymerization (ATRP) of methyl ether poly(ethylene glycol) methacrylate (mPEGMA), poly(propylene glycol) methacrylate (PPGMA) and dimethylaminoethyl methacrylate (DMAEMA) in the presence of ethyl α‐bromoisobutyrate as ATRP initiator. The poly(PEG/PPG/DMAEMA) terpolymer was featured with a cationic backbone containing PDMAEMA segments and amphiphilic side chains composed of hydrophilic PEG and hydrophobic PPG short branches. The copolymer was characterized by ¹H NMR, Fourier transform IR and gel permeation chromatography. The thickening behavior of this copolymer in a surfactant system (sodium dodecyl sulfate, SDS) was extensively investigated by a rheological study. It was found that the copolymer can effectively thicken the SDS surfactant system at low concentrations of both copolymer and surfactant. More interestingly, the thickened SDS system by this copolymer showed dramatic pH responsive rheological behavior in the pH range 4–10. Thus the rheological behavior of the thickened SDS system was tunable by pH value. Based on our findings, a novel thickening mechanism is proposed for this kind of cationic brush‐like terpolymer. This kind of cationic brush‐like copolymer would be a new type of rheology modifier for advanced hair/skin care systems. © 2014 Society of Chemical Industry     

Sorption of lysozyme by HEMA copolymer hydrogels

Sorption of lysozyme by 2-hydroxyethyl methacrylate (HEMA) copolymer hydrogels was studied as a function of pH and gel composition. Three types of HEMA gels were synthesized: neutral (HEMA), acidic (HEMA + acrylic acid), and basic (HEMA + dimethylaminoethyl methacrylate). Each gel was synthesized at four initial volume fractions to obtain different equilibrium swelling ratios and microstructures. Sorption as a function of time was measured for each gel at pH 7, 7.5, and 8. The rate of uptake by the acidic gels was more rapid than that by the neutral gels: To sorb 90% of the protein required only 1 h for the acidic gels but 15 days for neutral gels. Lysozyme did not adsorb or partition into the basic gels. The fractional approach to equilibrium was most rapid for the more swollen gels, and the effect of pH was small. The results reported here may be useful for rational design of new biomaterials where it is desirable to know the relative magnitude of the effects of composition, synthesis, and pH on protein sorption. © 1996 John Wiley & Sons, Inc.     

Swelling behaviour of a new kind of polyampholyte hydrogel composed of dimethylaminoethyl methacrylate and acrylic acid

Poly[(dimethylaminoethyl methacrylate)‐co‐(acrylic acid)] [poly(DMAEMA‐co‐AAc)] hydrogels have been synthesized by UV‐induced copolymerization of dimethylaminoethyl methacrylate (DMAEMA) and acrylic acid monomer. The effects of pH and ionic strength on the swelling behaviour of poly(DMAEMA‐co‐AAc) hydrogels were investigated in detail. It was found that there is minimal equilibrium swelling ratio (ESR) for the hydrogels with the change of pH, and the pH at minimal ESR of the hydrogels was defined by the isoelectric points (IEP), similar to the situation with protein molecules. The IEP of the hydrogels shifted to higher values with increase in the DMAEMA content in the hydrogels. Antipolyelectrolyte behaviour of the hydrogels at a pH near the IEP was observed as well, and the ESR increased with increasing ionic strength. The study of swelling kinetics of the hydrogels showed that the swelling process was Fickian at the IEP and non‐Fickian when the pH deviated from the IEP. Copyright © 2003 Society of Chemical Industry     

Preparation and application in drug controlled delivery of pH‐sensitive P(CE‐co‐DMAEMA‐co‐MEG) hydrogel

A pH‐sensitive hydrogel [P(CE‐co‐DMAEMA‐co‐MEG)] was synthesized by the free‐radical crosslinking polymerization of N,N‐dimethylaminoethyl methacrylate (DMAEMA), poly(ethylene glycol) methyl ether methacrylate(MPEG‐Mac) and methoxyl poly(ethylene glycol)‐poly(caprolactone)‐methacryloyl methchloride (PCE‐Mac). The effects of pH and monomer content on swelling property, swelling and deswelling kinetics of the hydrogels were examined and hydrogel microstructures were investigated by SEM. Sodium salicylate was chosen as a model drug and the controlled‐release properties of hydrogels were pilot studied. The results indicated that the swelling ratios of the gels in stimulated gastric fluids (SGF, pH = 1.4) were higher than those in stimulated intestinal fluids (SIF, pH = 7.4), and followed a non‐Fickian and a Fickian diffusion mechanism, respectively. In vitro release studies showed that its release rate depends on different swelling of the network as a function of the environmental pH and DMAEMA content. SEM micrographs showed homogenous pore structure of the hydrogel with open pores at pH 1.4. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40737.     

pH‐reversible hydrogels. IV. Swelling behavior of the 2‐hydroxyethyl methacrylate‐co‐acrylic acid‐co‐sodium acrylate copolymeric hydrogels

A series of 2‐hydroxyethyl methacrylate (HEMA) and sodium acrylate (SA50) copolymeric gels were prepared from HEMA and the anionic monomer SA50 with various molar ratios. The influence of SA50 on the copolymeric gels on their swelling behavior in deionized water at different temperatures and various pH buffer solutions was investigated. Results indicated that the poly(2‐hydroxyethyl methacrylate) (PHEMA) hydrogels exhibited an overshooting phenomenon in their dynamic swelling behavior. The maximum overshooting value decreased with increasing of the temperature. The same results were also found in the HEMA/SA50 copolymeric gels with a lower SA50 content. On the contrary, the overshooting phenomenon for HEMA/SA50 copolymeric gels with a higher content of SA50 was exhibited only under higher temperature (over 35°C). These copolymer gels were used to assess drug release and drug delivery in this article. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1360–1371, 2001     

Poly(2-hydroxyethyl methacrylate-co-sulfobetaine) hydrogels. II. Synthesis and swelling behaviors of the [2-hydroxyethyl methacrylate-co-3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate] hydrogels

A series of the 2-hydroxyethyl methacrylate/3-dimethyl-(methacryloyloxyethyl)ammonium propane sulfonate (HEMA/DMAPS) copolymeric gels was prepared from various molar ratios of HEMA and the zwitterionic monomer DMAPS. The influence of the amount of the zwitterionic monomer in the copolymeric gels on the swelling behaviors in water, various saline solutions, and temperature was investigated. The results indicate that the PHEMA hydrogel (D0) and lower DMAPS content of the HEMA/DMAPS copolymeric gel (D1) exhibit overshooting phenomena in the dynamic swelling behavior. The maximum overshooting value decreases with increase in temperature. In the equilibrium swelling ratio, the PHEMA hydrogel exhibits a minimum swelling ratio at 55°C. Then, the minimum swelling ratio diminishes gradually with increasing of the DMAPS content in the HEMA/DMAPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/DMAPS copolymeric gels increase rapidly with increasing of concentration of the salt with a smaller ratio of the charge/radius. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2021–2034, 1998     

温度和pH双重敏感性P(DEA-co-DMAEMA)/Na2WO4水凝胶的合成与表征

以N,N-二乙基丙烯酰胺(DEA)和甲基丙烯酸二甲氨基乙酯(DMAEMA)为单体,N,N-亚甲基双丙烯酰胺(BIS)为交联剂,采用一锅法制备了温度和p H双重响应性P(DEA-co-DMAEMA)/Na_2WO_4水凝胶。考察了Na_2WO_4的引入对水凝胶的结构、温度和p H响应性能的影响。结果表明:复合水凝胶中除了化学交联外,还存在Na_2WO_4与聚合物间由于氢键和配位作用产生的物理交联;复合水凝胶的低临界相转变温度(LCST)随着Na_2WO_4质量分数的增加呈线性降低,当Na_2WO_4质量分数从0增至3%时,LCST由41.6℃降至34.4℃;复合水凝胶表现出双重p H响应性,即在酸性条件下溶胀,中性条件下溶胀率减小,碱性条件下溶胀率又升高。     

Synthesis of porous poly[oligo(ethylene glycol) methyl ether methacrylate] gels that exhibit thermosensitivity in highly concentrated aqueous NaCl solution

The polymerization of 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) in 20 wt% aqueous ethanol solution and oligo(ethylene glycol) methyl ether methacrylate (OEGMA₃₀₀, M_n = 300 g mol^?1) in water was carried out in the presence of a crosslinker. Polymerization at temperatures above the lower critical solution temperature (LCST) yielded the corresponding porous poly[oligo(ethylene glycol) methyl ether methacrylate] gels by polymerization-induced phase separation. The resulting porous gels showed rapid swelling-deswelling in water. The temperature dependency of the equilibrium swelling ratio of the gels was investigated in several concentrated aqueous NaCl solutions. At 20 °C, the equilibrium swelling ratios of the POEGMA₃₀₀ gel obtained from OEGMA₃₀₀ were largely unaffected by NaCl concentration; however, above 30 °C, they decreased with increasing NaCl concentration. Therefore, the POEGMA₃₀₀ gel showed sharp and high thermosensitivity in highly concentrated aqueous NaCl solutions. Similar swelling behaviors were observed for PMEO₂MA gel, which was prepared from MEO₂MA.     

Poly(N,N-dimethylaminoethyl methacrylate)/graphene oxide hybrid hydrogels: pH and temperature sensitivities and Cr(VI) adsorption

Different amounts of graphene oxide (GO) were incorporated to N,N-dimethylaminoethyl methacrylate (DMAEMA), fabricating a series of pH and temperature dual sensitive PDMAEMA/GO hybrid hydrogels by in situ polymerization. Their microscopic network structures as well as swelling properties and Cr(VI) adsorption were characterized. The equilibrium swelling ratios (ESR) of hydrogels increased significantly with 0.5 wt% GO feeding of DMAEMA amount, and then decreased with further GO loading increasing. All hydrogels showed obvious deswelling when pH value of swelling mediums increased from 5 to 10 gradually. At pH 7, hydrogels revealed slight ESR increment with temperature up to 50 °C, above which obvious deswelling occurred. In pH 8 buffer, 0.5 wt% of GO loading triggered lower critical solution temperature (LCST) to decrease by 3 °C, and 2–7 °C increment was observed when 1–6 wt% of GO was loaded, as compared with that of GO-free PDMAEMA hydrogel. Cr(VI) adsorption of hydrogels was also improved by the introduction of GO to some extent, and the maximum Cr(VI) adsorption of 180 mg/g was realized, indicating that the obtained PDMAEMA/GO hybrid hydrogels possess excellent adsorption performance.     

Synthesis and characterization of amphiphilic conetworks based on multiblock copolymers

Model amphiphilic conetworks based on cross-linked block copolymers of the hydrophilic ionizable 2-(dimethylamino)ethyl methacrylate (DMAEMA, 25 nominal units per block) and the hydrophobic n-butyl methacrylate (BuMA, 5 nominal units per block) bearing three, five, seven and nine blocks were synthesized using group transfer polymerization. 1,4-Bis(methoxytrimethylsiloxymethylene)cyclohexane and ethylene glycol dimethacrylate were used as the bifunctional initiator and the cross-linker, respectively. Network synthesis was performed by sequential monomer/cross-linker additions to the reaction flask, which was pre-loaded with tetrabutylammonium bibenzoate (polymerization catalyst), tetrahydrofuran (THF, solvent), and initiator. All linear conetwork precursors were characterized using gel permeation chromatography and proton nuclear magnetic resonance spectroscopy and found to have molecular weights (MWs) and compositions reasonably close to the theoretically expected values. All polymer conetworks were characterized in terms of their degree of swelling (DS) in THF, in neutral water, and in aqueous media as a function of the solution pH. It was found that the DSs were highest in acidic pH due to the repulsive forces and the osmotic pressure developed by the ionization of the DMAEMA units. Intermediate values of the DSs were observed in THF, whereas the lowest DSs were measured in neutral water. In THF, the DSs increased with the MWs of the (final) linear (co)polymer precursors, while in acidic water the DSs increased with the DMAEMA content in the (co)networks.     

Temperature and pH‐Sensitive Swelling Behavior of Binary DMAEMA/4VP Grafts on Poly(propylene) Films

Poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) is a polymer or hydrogel that is both thermosensitive and pH sensitive, with a low critical solution temperature (LCST) around 38 °C and a pH critical point of 2.5. Poly(4‐vinylpyridine) (P4VP) shows pH sensitivity with a critical point of 5.1. Grafting of stimuli‐sensitive polymers onto mechanically durable poly(propylene) (PP) substrates was used in this study. We have focused on the influence of temperature and pH on the response of binary graft films produced by gamma irradiation in one and two steps. An LCST‐type hydration transition in the grafts was observed by measuring swelling of the films and water contact angle at different temperatures and pH. An upper critical solution temperature (UCST)‐type behavior was also observed by swelling PP‐g‐DMAEMA and DMAEMA/4VP binary grafting onto PP films at pH 2.2.

     

Molecular weight effect on swelling of polymer gels in homopolymer solutions: a fluorescence study

A novel technique based on in situ steady state fluorescence measurements is introduced for studying swelling processes of gels formed by free radical crosslinking copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDM) in homopolymer solutions. Gels were prepared at 55±2 °C for various EGDM contents. After drying these gels, swelling experiments were performed in chloroform solution of anthracene labeled poly(methyl methacrylate) (An-PMMA) in various molecular weights at room temperature by real time monitoring of anthracene fluorescence intensity. Anthracene labeled PMMA chains having various molecular weights were prepared by atom transfer radical polymerization at 90 °C. During the swelling experiments, it was observed that anthracene emission intensities increased due to trapping of An-PMMA chains into the gel as the swelling time is increased. The trapping of An-PMMA chains in swollen gel, increase by obeying parabolic law in time. Penetration time constant, τ of PMMA chains were measured and found to be increased as the crosslinker density of gel is increased. It is observed that τ values are much higher for high molecular weight An-PMMA chains than low molecular weight chains in all gel samples.     

Poly[2-(hydroxyethyl methacrylate)-co-(sulfobetaine)]s hydrogels: 1. Synthesis and swelling behaviors of the 2-(hydroxyethyl methacrylate)-co-2-(vinyl-1-pyridinium propane sulfonate) hydrogels

A series of the 2-hydroxyethyl methacrylate/2-vinyl-l-pyridinium propane sulfonate (HEMA/VPPS) copolymeric gels have been prepared from HEMA and zwitterionic monomer VPPS of various molar ratios. The influence of the amount of VPPS in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures was investigated. Results indicate that the PHEMA hydrogels exhibit an overshooting phenomenon in their dynamic swelling behavior. The maximum overshooting value decreases with increasing temperature. The same results are also shown for the lower VPPS content HEMA/VPPS copolymeric gels. In the equilibrium swelling ratio, the PHEMA hydrogel exhibits a minimum swelling ratio at 55 °C. Then, the minimum swelling ratio disappears gradually with increasing VPPS content in HEMA/VPPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/VPPS copolymeric gels increase rapidly with increasing salt concentration, for salts with a smaller ratio of charge/radius.     

Alkali‐responsive membrane prepared by grafting dimethylaminoethyl methacrylate onto ethylene vinyl alcohol copolymer membrane

An alkali‐responsive membrane was prepared by grafting dimethylaminoethyl methacrylate (DMAEMA) onto ethylene vinyl alcohol copolymer (EVAL) membrane using ultraviolet (UV) irradiation graft polymerization. A subtranslucent state of EVAL membrane swelling in the DMAEMA solution was observed, and such a state enabled the passage of UV light through all the pores, inducing graft polymerization inside the pores and on the back. Attenuated total reflectance Fourier‐transform infrared spectrometer (ATR‐FTIR), X‐ray photoelectron spectroscopy (XPS), field‐emission scanning electron microscopy (FESEM), and energy‐dispersive X‐ray spectroscope (EDX) confirmed that the poly(DMAEMA)‐grafted chains existed not only on the top surface, but also inside the pores and on the back. Atomic force microscopy (AFM) and nitrogen adsorption analysis confirmed that the grafted chains collapsed in air, and decreased the surface roughness, surface area, and pore size of the grafted membranes. Alkali‐responsive properties of the poly(DMAEMA)‐grafted EVAL membrane (i.e., contact angle, permeability, and selectivity) were observed in the pH range of 9–10. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41775.