• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Dynamic swelling performance of hydrophobic hydrogels

    2022-06-20 06:22:40HuiGuoJunxinChenZingWngHongLeiGuoWeiHongXiolinWng
    Chinese Chemical Letters 2022年4期

    Hui Guo,Junxin Chen,Zing Wng,Hong Lei Guo,Wei Hong,Xiolin Wng

    a School of Chemical Engineering and Technology,Sun Yat-sen University,Zhuhai 519082,China

    b Department of Mechanics and Aerospace Engineering,Southern University of Science and Technology,Shenzhen 518055,China

    c School of Pharmacy and State Key Laboratory of Quality Research in Chinese Medicine,Macau University of Science and Technology,Macao,China

    1 These authors contributed equally to this work.

    ABSTRACT Conventional gels manifest monotonous swelling or shrinking performance upon immersing in solvents until reaching an equilibrium state.Recently,we discovered that the“hydrophobic hydrogels”prepared from hydrophobic polymer networks demonstrated dynamic swelling performance without equilibrium states.Upon water immersion,the gels expanded tremendously at the first stage until reaching a swelling peak;subsequently,the gels shrunk at an extremely slow rate.While this phenomenon endows the material with an unusual feature,more efforts are highly demanding for the full understanding of this performance.Herein,we systematically investigate the hydrophobic hydrogels’swelling kinetics by screening the organic solvent dependence,polymer effect,and temperature impact.It is revealed that the chemical structure of gels greatly influences the swelling kinetics.The higher the networks’hydrophobicity,the slower the swelling kinetics.Meanwhile,organic solvents demonstrate a limited effect on the dynamic swelling performance.Moreover,higher temperature significantly accelerates the whole volume change process.Based on the swelling performance,we further develop hydrogel-based soft devices with timeprogrammable two-dimensional and three-dimensional shape-shifting performances.

    Keywords:Hydrophobic hydrogels Swelling kinetics Shape-shifting device Time-dependence Thermodynamically unstable state

    Gels are defined as three-dimensional crosslinked polymer networks infiltrated with solvents.While the networks maintain gels with elastic performance,the solvent fillers endow the materials with satisfactory biocompatibility,super wetness,and suitable softness[1].During the past few decades,gels have received intensive interest for versatile engineering and biological applications[2–7].All of the functions are highly dependent on the intrinsic features of gels.In particular,one favorable property of gels is their ability to change volume when immersing in a solvent[8].Based on this particularity,these soft materials can serve as potential candidates for soft actuators[9],valves[10]and rapid hemostasis[11].

    Normally,a polymer hydrogel swells in a thermodynamically compatible solvent from the preparation stage.In contrast,the gel tends to shrink(deswell)in a noncompatible solvent driven by osmotic pressure.From a statistical macroscopic theory,the equilibrium state is achieved by a minimum of the Gibbs free energy[12].More precisely,the thermodynamic force of gels’volume change is determined by the change of free energy of mixing,change of elastic energy,and mixing of ions with solvent according to Flory and Rehner[13].Once a gel attains a thermodynamically stable state(swelling equilibrium state),no driving force exists to swell or shrink the gel as the osmotic pressure gap across the gel’s interface disappears.Consequently,the swelling/deswelling of gel manifests a monotonous performance under fixed environmental conditions.Starting from the swelling equilibrium state,a gel may undergo volume change to fulfill versatile functionalities only if the material is imposed with environmental triggers(e.g.,temperature[14–16],pH[17,18],light[19,20],magnetic field[21],salt[22],solvent[23])or undergo chemical change(e.g.,hydrolysis[24],crosslinking[25],isomerization[26]).

    Recently,a kind of“hydrophobic hydrogels”composed of hydrophobic polymer networks while maintaining super high water content has been discovered[27,28].Besides this particular composition,these hydrophobic hydrogels have a unique fruitlike structure,selective water absorption capacity,and more interestingly,dynamic swelling processes.The gels were prepared by immersing hydrophobic organo-gels with omniphilic organic solvents in water.Upon such solvent exchange,instantaneously that the hydrophobic polymer chains phase separate to form condensed surface layers,which serve as a semipermeable membrane to maintain the organic solvent inside gels while staying open to water.Therefore,the organic solvent forms high osmotic pressure to absorb external water inside and swell the materials.Macroscopically,the gels expanded at the first stage and reached a swelling peak,thereafter the gels shrunk at an extremely slow rate(Fig.1).During the whole process,no swelling equilibrium state is observed as that for conventional gels,and the swelling ratio demonstrates obvious time dependence.

    Fig.1.(a)Scheme of swelling kinetics of hydrophobic hydrogels and conventional hydrogels upon solvent exchange.(b)Photos of PMEA gels swelling performances at different stages.

    Benefitting from this unusual swelling process,it is feasible to program the volume change of hydrogels with time.In this work,we report the systematical investigation of factors that influence the hydrophobic hydrogels’swelling kinetics,including organic solvent dependence,polymer effect,and temperature impact.Both gels’ chemical structure and environmental temperature greatly influence the swelling kinetics and ratio.Based on the swelling performance,we further develop time-programmable soft shape-shifting materials,where the two-dimensional(2D)and three-dimensional(3D)shape-shifting performances can be finely tuned by controlling immersing time.

    Upon the solvent exchange by immersing organo-gels in water,only three components are on the scene:organic solvent,polymer network,and water.Water may enter the gels with osmotic pressure as a driven force,while organic solvents infiltrated the organo-gels may come out to mix with water.The two processes compete with each other and lead to abnormal swelling or normal shrinking of gels.According to our previous study[27],only the organo-gels with omniphilic organic solvents have a higher affinity for water than for polymer network displayed such type of abnormal volume expansion.Taking our previous system of polymer poly(methyl acrylate)(PMA)gels for example,DMSO(dimethyl sulfoxide),DMF(N,Ndimethylformamide),NMP(N-methyl-2-pyrrolidone),DMAc(N,Ndimethylacetamide),and NMF(N-methylformamide)are such kind of solvent(termed as“swelling solvent”)to swell PMA gels,while other solvents such as acetone,THF(tetrahydrofuran)and MeCN(acetonitrile)are account for the normal shrinkage of PMA gels.

    In the first place,we investigated the influence of organic solvent on the gels’swelling performance with PMA gels.The fabrication of PMA organo-gels was simply realized with UV-cure polymerization with monomer and crosslink molecules in(DMSO).Subsequently,the PMA discoid gels were immersed omniphilic organic solvent to reach an equilibrium state,followed by the solvent exchange in a large amount of water.As depicted in Fig.2a,PMA organo-gels pre-equilibrated in the five swelling organic solvents all manifested obvious swelling performance upon immersion in water.Just after a few hours’solvent exchange process,the gels’volume boosted 5-8 times.In contrast,the organo-gels pre-swelled in acetone,THF,and MeCN led to fast shrinkage(Fig.S1 in Supporting information).To characterize the swelling kinetics,we first eliminated the effect induced by gels’size effect.According to Fick’s Laws of diffusion[29],the diffusion time of given species across a fixed layer thickness is proportional to the square of the layer’s thickness.For better comparison,the swelling time is normalized by the square of the initial sample thickness(time/t2).From our previous work,this normalization approach well fits samples with different initial thicknesses.In addition,two parameters are defined to simplify our following discussion:Qmax,i.e.,the maximum swelling ratio;tmax,i.e.,the normalized time to reachQmax.From the time profiles of the swelling ratio depicted in Figs.2b and c,no evident difference occurs among 5 groups of samples concerning theQmax,as all the maximum swelling ratios are around 6-8.Similarly,theTmaxdemonstrates weak dependence on organic solvents,as most of the values are around 20 h/mm2.The only exception is DMF,which may be attributed to the large gap in sampling.Moreover,the diffusion coefficient of water during the solvent exchange was also carried out to assess the organic solvent impact with a typical gravimetric method[30].Similar to the other parameters,all the samples from different organic solvents demonstrate comparable diffusion rates.From all these data,it is clearly demonstrated that organic solvent has a rather limited effect on the kinetics of such abnormal swelling.

    From our previous preliminary work,it has been verified that the organic solvent residues played a critical role in the type of abnormal swelling performance[27].The more organic remained,the higher osmotic pressure was generated,and the larger swelling degree was achieved.Indeed,unlike the conventional hydrogels where miscible solvent escapes from the soft materials rapidly during the solvent exchange,still a large amount of organic solvents was left inside the gel after swelling in water for 16 h(Fig.S2 in Supporting information).Between different swelling solvent groups,a minor difference exists,which brings about a slight deviation in osmotic pressure between different gels.Consequently,no significant difference in swelling performance presents.

    Next,the significance of the polymer effect has been fully screened.Whereas the organic solvent infiltrated inside the network displays a slight influence on the swelling ratio and kinetics,the role played by the polymer network is extremely prominent.As shown in Fig.3a,the swelling kinetics of 9 polymers organogels demonstrated a striking difference.Almost all the samples exhibited a dynamic swelling performance with no swelling equilibrium state,except for poly(phenyl acrylate)(PPA)sample that exhibited an equilibrium-like swelling process with a relatively lower maximum swelling ratio.Compared to other samples with polymer glass transition temperature(Tg)lower than observation temperature(25 °C),the PA polymer has a rather highTg(63 °C).Therefore,the swelling performance for PPA gels can be account for the plasticity of the frozen phase separation structure during swelling,which increases the swelling resistance but diminishes the contractile elasticity.From the supplementary rheological test,the rubbery like PPA-DMSO organo-gel turned into a fragile plastic PPA-hydrogel after just swelling in water for 2 min(Fig.S3 in Supporting information).As a result,the gel maintained a constant volume after long-term immersion even without enough osmotic pressure induced by residue solvents.In contrast,immersed at a temperature higher than Tg,this gel presented again a dynamic volume change without equilibrium state,while the maximum swelling degree was remarkably enhanced compared to that at low temperature(Fig.S4 in Supporting information).At the same time,the other 8 types of organo-gels exhibited different swelling ratios and kinetics in water(Fig.3b).On one hand,the polymer gels which has only poly(ethylene glycol)(PEG)side chains,such as PMEA,PCBA,tended to swell rapidly.This is especially the case for PMEA organo-gels,which took only around 1 h/mm2to reach thetmax.On the other hand,the polymers that have bulk aryl hydrophobic groups,such as PBnA,PPHEA,manifested a very long swelling process prior to the maximum swelling degree.Thetmaxachieved by PBnA gel(73.1 h/mm2)is nearly two decades higher than that of PMEA.Meanwhile,the longer swelling period of PBnA and PPHEA led to the highest swelling ratio.Between the two critical situations,other polymer gels are located with mild swelling kinetics and maximum swelling ratio.The difference induced by polymer is more prominent and comparative by comparing the diffusion coefficient(D).Whereas PBnA gels showed a D value of 5.9 × 10-13m2/s,PMEA demonstrated a more than 100 higher value of 8.0 × 10-11m2/s.

    Fig.2.(a)Time profiles of swelling ratio(Q)of PMA organo-gels from the different organic solvent after being immersed in water at 25 °C.(b)Time/thickness2 profiles of Q of PMA organo-gel from different organic solvent.(c) tmax, Qmax and water diffusion coefficient(D)of the different PMA organo-gels.The initial size of the disc shape samples was 33 mm in diameter and around ~0.67 mm in thickness.The chemical structures of the solvent are illustrated below the figure.

    Fig.3.(a)Time profiles of swelling ratio(Q)of different polymer organo-gels from DMSO after being immersed in water at 25 °C.(b) tmax, Qmax and water diffusion coefficient(D)of different organo-gels.The initial size of the disc shape samples was 33 mm in diameter and around ~2.0 mm in thickness.The chemical structures of the linear polymers are illustrated below the figure.Note that all the linear polymers bear glass transition temperature(Tg)lower than room temperature,except PPA whose Tg is 63 °C[32].

    This distinct performance can be elucidated with the aid of the semi-permeable membrane hypothesis developed in our previous study[27].Upon solvent exchanging from good solvent to poor solvent,the phase separation of polymer network restrains a large amount of organic solvent and generates high osmotic pressure to swell the gel at the first stage.Over time,organic solvent slowly leaking from the phase-separated membrane decreases the osmotic pressure,therefore gives rise to the further deswelling of the materials.The more hydrophobic the membrane,the less susceptible that organic solvent and water diffuse across the system,the higher the osmotic pressure generated.Consequently,the materials achieve the higher maximum swelling ratio.These are typically the stories for PBnA and PPHEA gels,where the hydrophobic benzyl side chains form solvent-proof membranes and the release of organic solvent becomes rather time-consuming.Consequently,slow swelling kinetics are revealed.In contrast,if the polymers are somehow hydrophilic with PEG side chains,the structure of the membrane is not finely fixed,thus facilitates the flux of both organic solvent and water and lead to fast swelling kinetics.

    Fig.4.Shape-shifting behaviors of hydrophobic hydrogels.(a)Scheme of the sandwich-like soft device upon solvent exchange process.(b)Time profiles of bending angle of three soft shape-shift materials(PMEA-PET film,PBnA-PET film,PMEAPET film-PBnA),the inset shows the definition of the bending angle(θ).(c-e)Twodimensional(2D)shape-shifting performances of three types of materials(PMEAPET,PBnA-PET,PMEA-PET-PBnA).(f)Three-dimensional(3D)shape-shifting performance of PMEA-PET-PBnA hydrogel.The initial size of the organo-gel layer was 0.2 mm in thickness.

    Besides intrinsic property,environmental factors such as temperature also significantly influence the swelling kinetic.As shown in Fig.S5(Supporting information),the kinetics is greatly enhanced upon raising the temperature.For PMEA gels,thetmaxat 60 °C is more than 20 times shorter than that at 5 °C.Consequently,the diffusion rate experiences a significant enhancement upon heating.At the same time,the maximum swelling ratioQmaxremains less unaffected at lower temperatures but presents descending trend at higher temperatures.

    Benefitting from this dynamic swelling process of such hydrophobic hydrogels,it is feasible to program the volume change of materials.For this purpose,sandwich-like materials were fabricated by two hydrophobic hydrogels with divergent swelling kinetics combining with non-swellable backing.As a representative illustration,PMEA and PBnA were prepared with polyethylene terephthalate(PET)film in the middle as a dimensional stable bonding medium(Fig.4a).In the first few minutes after soaking the sandwich-like PMEA-PET-PBnA sample in water,the violet PMEA layer swelled much more promptly and greatly than the opposite yellow layer of PBnA hydrogel,driving the bilayer hydrogel strip to bend in the direction of the yellow side(Figs.4b-e).Later,after the swelling equilibrium state of PMEA and with the continuous expansion of PBnA part,the swelling volume difference between the two layers decreases,resulting in the full recovery of binding performance.Then the bilayer hydrogel strip started to shift the bending direction to the violet side since the swelling volume of PBnA hydrogel is more important than that of the PMEA hydrogel.Besides the sandwich-like samples,hydrogel-PET singlelayer materials also demonstrate similar dynamic shape-shifting performance.Both of the single-layer hydrogel strips could finally bend to full or nearly complete circles.Moreover,heating can significantly accelerate the shape-shifting performance and shorten the response time.

    In addition to the 2D variation,3D self-actuation like a flower has been designed as well.As shown in Fig.4f,a piece of PMEAPET-PBnA organo-gel was cut into the shape of a long-sawtooth and then was rolled one or two circles along the long side to form the shape of a flower bud.When it was immersed in water,the blossom opened to the maximum at the first few minutes and then began to close up like an Epiphyllum.Accordingly,by rationally adjusting the composition of the two layers,as well as the temperature of the permeant solvent,the asymmetricity in the hydrophobicity of the hydrogel can be changed and the amplitude along with the speed or the duration of self-actuation behavior can be regulated.Furthermore,by designing the shape of the bilayer gel or the patterned distributions[31]of the different gels,the hydrogel could deform into 2D or 3D complex structures spontaneously,indicating considerable potential as time-programmable soft shape-shifting materials.

    In this work,we systematically investigate the hydrophobic hydrogels’dynamic swelling process upon solvent exchange.The organic solvent dependence,polymer effect,and temperature impact are systematically studied by extracting three parameters,namely:the maximum swelling ratio(Qmax),time to reach maximum swelling ratio(tmax),and the diffusion coefficient of water(D).It is verified that the chemical structure of gels greatly influences the swelling kinetics.The higher the polymer networks’hydrophobicity,the larger thetmaxand the lower the D.Meanwhile,organic solvents that can swell the gels during the solvent exchange process demonstrates a limited effect on the dynamic swelling performance.Moreover,higher environmental temperature significantly accelerates the whole volume change process.Based on the swelling performance,we further develop timeprogrammable soft shape-shifting materials with distinct polymer gels,which demonstrate rapid 2D and 3D shape-shifting materials upon solvent exchange.

    With this study,we hope to inspire readers to take a new look at gels’swelling process.Other dynamic swelling processes are also likely by finely tuning the swelling driven force.In addition,we anticipate that the dynamic swelling performance of the hydrophobic hydrogels may endow them with other promising applications in the future.

    Declaration of competing interest

    The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

    Acknowledgment

    The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(NSFC,Nos.51903253,51903257),Natural Science Foundation of Guangdong Province of China(Nos.2019A1515011150,2019A1515011258),Macau University of Science and Technology Foundation(No.FRG-19-003-SP),and the Science and Technology Development Fund of Macao(Nos.FDCT 0009/2019/A,0083/2019/A2,0007/2019/AKP,0009/2020/AMJ).

    Supplementary materials

    Supplementary material associated with this article can be found,in the online version,at doi:10.1016/j.cclet.2021.09.015.

    在线观看人妻少妇| 午夜福利视频在线观看免费| 啦啦啦 在线观看视频| 久久久久久久久久久久大奶| 在线观看三级黄色| 欧美 亚洲 国产 日韩一| 丝瓜视频免费看黄片| 亚洲国产精品999| 精品国产乱码久久久久久男人| 69精品国产乱码久久久| 啦啦啦在线免费观看视频4| 午夜激情av网站| 国产精品麻豆人妻色哟哟久久| 国产免费现黄频在线看| 菩萨蛮人人尽说江南好唐韦庄| 日本爱情动作片www.在线观看| 下体分泌物呈黄色| 另类亚洲欧美激情| 日韩一本色道免费dvd| 久久久久国产一级毛片高清牌| 男男h啪啪无遮挡| 亚洲av综合色区一区| 免费看不卡的av| 伊人亚洲综合成人网| 国产一区亚洲一区在线观看| 久久久久网色| 国产色婷婷99| 国产精品久久久久久人妻精品电影 | 18在线观看网站| 亚洲综合色网址| 夜夜骑夜夜射夜夜干| av线在线观看网站| 国产熟女欧美一区二区| 精品久久蜜臀av无| 久久久久精品性色| 久久毛片免费看一区二区三区| 久久99一区二区三区| 中国三级夫妇交换| 久久久久精品性色| 在线观看免费视频网站a站| 国产成人精品无人区| 18禁裸乳无遮挡动漫免费视频| 精品国产国语对白av| 成年av动漫网址| 久久鲁丝午夜福利片| 两性夫妻黄色片| 久久午夜综合久久蜜桃| 欧美日韩av久久| av在线app专区| 伦理电影大哥的女人| 最黄视频免费看| 一级毛片电影观看| 一级黄片播放器| 女人高潮潮喷娇喘18禁视频| 中文字幕人妻丝袜制服| 两性夫妻黄色片| 美女扒开内裤让男人捅视频| 欧美乱码精品一区二区三区| 国产一级毛片在线| 国产av精品麻豆| 性少妇av在线| 啦啦啦中文免费视频观看日本| 国产精品国产三级国产专区5o| 国产av一区二区精品久久| 麻豆av在线久日| 久久久精品94久久精品| 青春草国产在线视频| 宅男免费午夜| 国产精品无大码| 亚洲情色 制服丝袜| 国产成人精品无人区| 青草久久国产| 少妇猛男粗大的猛烈进出视频| 女人被躁到高潮嗷嗷叫费观| 伦理电影大哥的女人| 日韩制服骚丝袜av| 欧美乱码精品一区二区三区| 在线观看一区二区三区激情| 国产女主播在线喷水免费视频网站| 自拍欧美九色日韩亚洲蝌蚪91| 超碰成人久久| 精品人妻在线不人妻| 久久精品亚洲熟妇少妇任你| 赤兔流量卡办理| 十八禁人妻一区二区| 国产日韩一区二区三区精品不卡| 蜜桃国产av成人99| 波野结衣二区三区在线| 亚洲国产中文字幕在线视频| 久热爱精品视频在线9| 国产成人午夜福利电影在线观看| 汤姆久久久久久久影院中文字幕| 精品一区二区三区av网在线观看 | 大话2 男鬼变身卡| 久久久精品94久久精品| 18禁观看日本| 亚洲七黄色美女视频| av片东京热男人的天堂| 久久久久国产精品人妻一区二区| 亚洲精品美女久久久久99蜜臀 | 国产免费视频播放在线视频| 波多野结衣av一区二区av| 欧美xxⅹ黑人| 国产精品免费大片| 老汉色∧v一级毛片| 在线天堂中文资源库| 免费在线观看黄色视频的| 午夜福利视频精品| 男人添女人高潮全过程视频| 亚洲激情五月婷婷啪啪| 丁香六月欧美| 在线观看一区二区三区激情| 亚洲美女黄色视频免费看| 观看美女的网站| 亚洲国产成人一精品久久久| 国产av精品麻豆| 国产男人的电影天堂91| 激情视频va一区二区三区| 欧美人与善性xxx| 亚洲熟女精品中文字幕| av电影中文网址| 久久狼人影院| 大香蕉久久成人网| 丰满少妇做爰视频| 人妻 亚洲 视频| 一级片免费观看大全| 国产人伦9x9x在线观看| 亚洲av在线观看美女高潮| 国产熟女欧美一区二区| 国产一区二区 视频在线| 国产成人欧美| 狠狠婷婷综合久久久久久88av| 精品午夜福利在线看| 久久久久精品性色| 国产一区二区激情短视频 | 99精品久久久久人妻精品| 卡戴珊不雅视频在线播放| 亚洲国产精品国产精品| 天天躁夜夜躁狠狠久久av| 国产视频首页在线观看| 伊人久久国产一区二区| 国产精品 国内视频| 精品第一国产精品| 新久久久久国产一级毛片| 久久人妻熟女aⅴ| 亚洲国产中文字幕在线视频| 午夜精品国产一区二区电影| 51午夜福利影视在线观看| 国产男女内射视频| 国产成人欧美| 欧美在线一区亚洲| 啦啦啦中文免费视频观看日本| 国产乱人偷精品视频| 国产成人精品久久久久久| www.精华液| 国产精品一二三区在线看| 在线天堂中文资源库| 女人精品久久久久毛片| 国产亚洲av高清不卡| 亚洲在久久综合| 亚洲国产av影院在线观看| 超碰成人久久| 国产探花极品一区二区| 大片电影免费在线观看免费| 美女视频免费永久观看网站| 亚洲七黄色美女视频| 国产精品一区二区在线不卡| 国产在线一区二区三区精| 欧美精品一区二区大全| 日日摸夜夜添夜夜爱| 精品亚洲成国产av| 91国产中文字幕| 精品亚洲乱码少妇综合久久| 欧美激情极品国产一区二区三区| 爱豆传媒免费全集在线观看| 亚洲av综合色区一区| 成人亚洲欧美一区二区av| 大片电影免费在线观看免费| 久久人人97超碰香蕉20202| 免费观看av网站的网址| 久久久久久久精品精品| 久久国产精品男人的天堂亚洲| 一级,二级,三级黄色视频| 丁香六月欧美| 久久狼人影院| 午夜福利网站1000一区二区三区| 18禁裸乳无遮挡动漫免费视频| 亚洲精品,欧美精品| 日本欧美视频一区| 国产精品久久久人人做人人爽| 免费高清在线观看日韩| 日韩av不卡免费在线播放| 又大又爽又粗| 超色免费av| 性少妇av在线| 成人漫画全彩无遮挡| 国精品久久久久久国模美| 一本大道久久a久久精品| 丰满少妇做爰视频| 999精品在线视频| av线在线观看网站| 人妻 亚洲 视频| 男女国产视频网站| 久久久久网色| 久久鲁丝午夜福利片| 中国三级夫妇交换| 国产成人欧美| 久久久亚洲精品成人影院| 免费观看性生交大片5| 午夜福利视频在线观看免费| 少妇被粗大猛烈的视频| 免费黄色在线免费观看| 你懂的网址亚洲精品在线观看| 男女高潮啪啪啪动态图| 国产日韩欧美亚洲二区| av免费观看日本| 一本久久精品| 欧美黄色片欧美黄色片| www.精华液| 国产精品久久久久久精品古装| 久久精品人人爽人人爽视色| 久久影院123| 97在线人人人人妻| av福利片在线| 国产亚洲av高清不卡| 亚洲av电影在线进入| 欧美国产精品一级二级三级| 亚洲国产精品国产精品| 制服诱惑二区| 9热在线视频观看99| 国产精品.久久久| svipshipincom国产片| 成年av动漫网址| 1024视频免费在线观看| 亚洲精品日本国产第一区| 亚洲精品美女久久久久99蜜臀 | 黄色怎么调成土黄色| 国产亚洲av片在线观看秒播厂| 18在线观看网站| 国产在视频线精品| 亚洲精品美女久久久久99蜜臀 | 国产精品免费视频内射| 欧美日韩一区二区视频在线观看视频在线| 啦啦啦中文免费视频观看日本| 国产精品香港三级国产av潘金莲 | 在线观看免费高清a一片| 两个人免费观看高清视频| 成人国产麻豆网| 欧美成人午夜精品| 高清黄色对白视频在线免费看| 中文字幕av电影在线播放| 日韩精品免费视频一区二区三区| e午夜精品久久久久久久| 一区二区三区激情视频| 1024视频免费在线观看| 一边摸一边抽搐一进一出视频| 黄色一级大片看看| 国产人伦9x9x在线观看| 午夜免费观看性视频| 亚洲欧洲国产日韩| 秋霞在线观看毛片| 亚洲国产欧美一区二区综合| 五月天丁香电影| 国产免费现黄频在线看| 国精品久久久久久国模美| 国产精品久久久人人做人人爽| 十分钟在线观看高清视频www| 激情视频va一区二区三区| 永久免费av网站大全| 91精品国产国语对白视频| 另类亚洲欧美激情| 国产精品欧美亚洲77777| 亚洲国产精品国产精品| 精品国产一区二区久久| 女的被弄到高潮叫床怎么办| 国产精品一国产av| 秋霞在线观看毛片| 亚洲精品日韩在线中文字幕| 在现免费观看毛片| 精品免费久久久久久久清纯 | 免费看av在线观看网站| 亚洲激情五月婷婷啪啪| 老司机在亚洲福利影院| 国产有黄有色有爽视频| 好男人视频免费观看在线| 在线精品无人区一区二区三| 久久午夜综合久久蜜桃| 亚洲精华国产精华液的使用体验| 中文精品一卡2卡3卡4更新| 国产精品久久久久久久久免| 欧美日韩视频精品一区| 97人妻天天添夜夜摸| 美女脱内裤让男人舔精品视频| 久久97久久精品| 午夜免费观看性视频| 各种免费的搞黄视频| 18禁观看日本| 日本一区二区免费在线视频| 国产一级毛片在线| 亚洲天堂av无毛| 少妇人妻精品综合一区二区| 久久久久久久久久久久大奶| 一边摸一边抽搐一进一出视频| 叶爱在线成人免费视频播放| 亚洲成人手机| 久久精品国产亚洲av涩爱| 搡老乐熟女国产| 日韩电影二区| 精品午夜福利在线看| 极品少妇高潮喷水抽搐| 一级毛片 在线播放| 亚洲精品国产av蜜桃| 亚洲av国产av综合av卡| 最近2019中文字幕mv第一页| 精品福利永久在线观看| 丝袜脚勾引网站| 香蕉丝袜av| 在线观看免费高清a一片| 精品少妇黑人巨大在线播放| 久久99热这里只频精品6学生| 国产av一区二区精品久久| 午夜激情久久久久久久| 国产又爽黄色视频| 午夜激情久久久久久久| 国产又爽黄色视频| 熟女少妇亚洲综合色aaa.| 国产一区有黄有色的免费视频| 欧美日韩一级在线毛片| 亚洲av综合色区一区| 超色免费av| 亚洲精品第二区| 纵有疾风起免费观看全集完整版| 色婷婷久久久亚洲欧美| 人成视频在线观看免费观看| av女优亚洲男人天堂| 在线天堂最新版资源| 中文字幕高清在线视频| videosex国产| 亚洲欧美一区二区三区久久| 欧美最新免费一区二区三区| 好男人视频免费观看在线| 91精品三级在线观看| 免费不卡黄色视频| 国产成人免费无遮挡视频| 97在线人人人人妻| 色94色欧美一区二区| av片东京热男人的天堂| 亚洲国产最新在线播放| 亚洲伊人色综图| 亚洲中文av在线| 最新的欧美精品一区二区| 人人澡人人妻人| 丰满饥渴人妻一区二区三| av视频免费观看在线观看| 亚洲精品视频女| 精品少妇久久久久久888优播| 美女视频免费永久观看网站| 高清视频免费观看一区二区| 国产国语露脸激情在线看| 男人爽女人下面视频在线观看| 丝袜美腿诱惑在线| 婷婷色综合www| 国产av精品麻豆| 天天躁日日躁夜夜躁夜夜| 成年人免费黄色播放视频| 天堂8中文在线网| 亚洲,欧美精品.| 成人18禁高潮啪啪吃奶动态图| 考比视频在线观看| 丰满迷人的少妇在线观看| 久久亚洲国产成人精品v| 制服人妻中文乱码| 精品人妻熟女毛片av久久网站| 黄片播放在线免费| 岛国毛片在线播放| 99九九在线精品视频| 天天添夜夜摸| 日本欧美国产在线视频| 一级片免费观看大全| 一二三四在线观看免费中文在| 久久天躁狠狠躁夜夜2o2o | 久久天堂一区二区三区四区| 人人澡人人妻人| 亚洲在久久综合| 啦啦啦中文免费视频观看日本| 看免费成人av毛片| 国产成人a∨麻豆精品| av有码第一页| 精品国产国语对白av| 美女脱内裤让男人舔精品视频| 最近手机中文字幕大全| 最近最新中文字幕大全免费视频 | 在线观看免费视频网站a站| 美女扒开内裤让男人捅视频| 午夜免费男女啪啪视频观看| 国产视频首页在线观看| 不卡视频在线观看欧美| 久久韩国三级中文字幕| 99国产综合亚洲精品| 亚洲自偷自拍图片 自拍| 亚洲七黄色美女视频| 丝袜脚勾引网站| 午夜日本视频在线| 久久久久久免费高清国产稀缺| 国产精品一国产av| 自线自在国产av| 精品一区二区三区四区五区乱码 | 国产一卡二卡三卡精品 | av视频免费观看在线观看| 国产精品一区二区在线不卡| 成年人免费黄色播放视频| 毛片一级片免费看久久久久| 国产伦人伦偷精品视频| 曰老女人黄片| 国产极品天堂在线| 18禁动态无遮挡网站| 日韩制服骚丝袜av| 精品国产一区二区三区四区第35| 欧美精品av麻豆av| 啦啦啦 在线观看视频| 嫩草影院入口| 最近最新中文字幕大全免费视频 | 18禁国产床啪视频网站| 日本av手机在线免费观看| 精品酒店卫生间| 丝袜美足系列| 精品国产露脸久久av麻豆| 我要看黄色一级片免费的| 亚洲七黄色美女视频| 国产精品免费视频内射| 哪个播放器可以免费观看大片| 免费黄网站久久成人精品| 亚洲一级一片aⅴ在线观看| 天天影视国产精品| 久久久精品94久久精品| 老汉色av国产亚洲站长工具| 大片免费播放器 马上看| 男女之事视频高清在线观看 | 男人舔女人的私密视频| 一本色道久久久久久精品综合| 国产精品香港三级国产av潘金莲 | 免费看av在线观看网站| 亚洲国产av新网站| 久久国产精品男人的天堂亚洲| 欧美另类一区| 亚洲精品美女久久久久99蜜臀 | 国产亚洲av片在线观看秒播厂| 久久久国产一区二区| 赤兔流量卡办理| 日本av手机在线免费观看| 午夜福利免费观看在线| 亚洲四区av| 视频在线观看一区二区三区| 欧美亚洲日本最大视频资源| 国产成人免费观看mmmm| 国产精品香港三级国产av潘金莲 | 国产一级毛片在线| 十分钟在线观看高清视频www| 成年动漫av网址| av天堂久久9| 国产探花极品一区二区| 亚洲精品国产av成人精品| 中文字幕人妻丝袜一区二区 | 国产成人精品福利久久| 亚洲综合精品二区| 天天躁夜夜躁狠狠久久av| 国产无遮挡羞羞视频在线观看| 精品国产乱码久久久久久小说| 日本91视频免费播放| 亚洲精品国产一区二区精华液| 国产不卡av网站在线观看| 日本av手机在线免费观看| 欧美日韩综合久久久久久| 久久精品亚洲熟妇少妇任你| 大香蕉久久成人网| 日日啪夜夜爽| 日本猛色少妇xxxxx猛交久久| 亚洲,欧美,日韩| netflix在线观看网站| 久久人妻熟女aⅴ| 韩国av在线不卡| 久久精品久久久久久噜噜老黄| 午夜影院在线不卡| 黄片播放在线免费| 国产熟女欧美一区二区| 国产日韩欧美视频二区| bbb黄色大片| 欧美97在线视频| 精品一区二区三区av网在线观看 | 91精品伊人久久大香线蕉| 亚洲七黄色美女视频| 一区二区三区激情视频| 99热网站在线观看| 一区福利在线观看| 亚洲精品久久午夜乱码| 天堂中文最新版在线下载| 麻豆精品久久久久久蜜桃| 国产麻豆69| 久久精品aⅴ一区二区三区四区| 亚洲精品国产色婷婷电影| 女性生殖器流出的白浆| 亚洲国产精品成人久久小说| 69精品国产乱码久久久| 久久国产精品男人的天堂亚洲| 黄片播放在线免费| 中文字幕人妻丝袜制服| 在线观看www视频免费| 操美女的视频在线观看| 亚洲人成网站在线观看播放| 热re99久久国产66热| 一级片免费观看大全| 丝袜在线中文字幕| 成人三级做爰电影| 黄色视频不卡| 在现免费观看毛片| 一区在线观看完整版| 午夜影院在线不卡| 精品少妇久久久久久888优播| 肉色欧美久久久久久久蜜桃| 国产乱来视频区| 精品国产一区二区久久| 久久毛片免费看一区二区三区| 男男h啪啪无遮挡| 亚洲国产欧美一区二区综合| 久热爱精品视频在线9| 欧美亚洲 丝袜 人妻 在线| 日韩一区二区三区影片| 国产极品天堂在线| 久久精品久久久久久久性| 欧美日本中文国产一区发布| 国产熟女午夜一区二区三区| 天天躁日日躁夜夜躁夜夜| 久久久久久久久久久免费av| 午夜久久久在线观看| 少妇被粗大的猛进出69影院| 国产男女内射视频| 久久久精品免费免费高清| 国产男女内射视频| 80岁老熟妇乱子伦牲交| 久久久久精品国产欧美久久久 | 十分钟在线观看高清视频www| 国产日韩欧美在线精品| 多毛熟女@视频| 考比视频在线观看| 欧美另类一区| 国产成人午夜福利电影在线观看| 国产精品三级大全| 考比视频在线观看| 久久久久精品国产欧美久久久 | svipshipincom国产片| 久久综合国产亚洲精品| 亚洲,欧美,日韩| 亚洲欧美清纯卡通| 亚洲熟女精品中文字幕| 日本欧美视频一区| 啦啦啦视频在线资源免费观看| 母亲3免费完整高清在线观看| 伊人久久大香线蕉亚洲五| av一本久久久久| 精品国产一区二区三区久久久樱花| 亚洲三区欧美一区| av又黄又爽大尺度在线免费看| 不卡视频在线观看欧美| 久久精品亚洲熟妇少妇任你| 欧美精品一区二区免费开放| 男人添女人高潮全过程视频| 中文字幕av电影在线播放| 日韩av不卡免费在线播放| 国产乱人偷精品视频| 在线观看国产h片| 叶爱在线成人免费视频播放| 亚洲精品国产区一区二| xxx大片免费视频| 国产一区二区三区综合在线观看| www日本在线高清视频| 哪个播放器可以免费观看大片| avwww免费| 91精品伊人久久大香线蕉| 日韩大码丰满熟妇| 国产野战对白在线观看| 人人澡人人妻人| 国产成人精品无人区| 嫩草影视91久久| 亚洲欧洲精品一区二区精品久久久 | 国产黄频视频在线观看| 国产精品麻豆人妻色哟哟久久| 久久精品久久精品一区二区三区| 一级片免费观看大全| 涩涩av久久男人的天堂| 久久综合国产亚洲精品| 亚洲精品aⅴ在线观看| 久久久久久人妻| 亚洲国产精品一区三区| 最近最新中文字幕大全免费视频 | 国产高清不卡午夜福利| 国产无遮挡羞羞视频在线观看| 欧美日韩亚洲国产一区二区在线观看 | 男人添女人高潮全过程视频| 中文字幕高清在线视频| 久久精品亚洲av国产电影网| 男人添女人高潮全过程视频| 好男人视频免费观看在线| 国产一区二区三区av在线| 男女无遮挡免费网站观看| 国产免费一区二区三区四区乱码| 欧美日韩成人在线一区二区| 亚洲国产毛片av蜜桃av| av在线播放精品| 亚洲精品久久久久久婷婷小说| 无遮挡黄片免费观看| 久久 成人 亚洲| 一级片免费观看大全| 老司机靠b影院| 日韩中文字幕视频在线看片| 午夜免费男女啪啪视频观看|