• <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.

    俄罗斯特黄特色一大片| 亚洲欧美精品综合久久99| 久久久久九九精品影院| or卡值多少钱| 在线免费观看的www视频| 精品人妻1区二区| 久久欧美精品欧美久久欧美| 妹子高潮喷水视频| 久久精品亚洲精品国产色婷小说| 亚洲精品国产一区二区精华液| 久久这里只有精品19| 俺也久久电影网| 欧美在线一区亚洲| 久久久久久大精品| 久久亚洲精品不卡| 91字幕亚洲| 亚洲一区中文字幕在线| 一级毛片精品| 级片在线观看| 免费看日本二区| 99热6这里只有精品| 国产成人aa在线观看| 毛片女人毛片| a在线观看视频网站| 在线观看美女被高潮喷水网站 | 香蕉丝袜av| 90打野战视频偷拍视频| 亚洲,欧美精品.| 久久99热这里只有精品18| 国产精品,欧美在线| 午夜免费观看网址| 亚洲自拍偷在线| 久久欧美精品欧美久久欧美| 天天躁夜夜躁狠狠躁躁| 又紧又爽又黄一区二区| 成人国产综合亚洲| 韩国av一区二区三区四区| 国产久久久一区二区三区| 精品欧美一区二区三区在线| 国产69精品久久久久777片 | 久久久国产成人免费| 一级片免费观看大全| 男女之事视频高清在线观看| or卡值多少钱| 亚洲精品粉嫩美女一区| 国产成年人精品一区二区| 婷婷六月久久综合丁香| 一级a爱片免费观看的视频| 黄色 视频免费看| 妹子高潮喷水视频| 久久精品91蜜桃| 国语自产精品视频在线第100页| 欧美高清成人免费视频www| 夜夜躁狠狠躁天天躁| 久久久久国产一级毛片高清牌| 亚洲国产中文字幕在线视频| 亚洲人成伊人成综合网2020| 黄色片一级片一级黄色片| 香蕉国产在线看| 麻豆国产av国片精品| 成年人黄色毛片网站| 亚洲五月天丁香| 久久亚洲真实| 精品久久久久久久末码| 久久亚洲真实| 国产精品美女特级片免费视频播放器 | 男女午夜视频在线观看| 国产在线精品亚洲第一网站| 麻豆国产av国片精品| 人成视频在线观看免费观看| 午夜福利免费观看在线| 变态另类丝袜制服| 国产精品免费一区二区三区在线| 精华霜和精华液先用哪个| 少妇熟女aⅴ在线视频| 日本一本二区三区精品| 亚洲精品国产一区二区精华液| 午夜激情福利司机影院| 欧美成狂野欧美在线观看| 国产亚洲欧美98| 人妻久久中文字幕网| 97超级碰碰碰精品色视频在线观看| 好男人在线观看高清免费视频| 免费搜索国产男女视频| 97人妻精品一区二区三区麻豆| 久久国产精品影院| 91大片在线观看| 亚洲avbb在线观看| 欧美色欧美亚洲另类二区| 非洲黑人性xxxx精品又粗又长| 一本一本综合久久| 99riav亚洲国产免费| 99久久无色码亚洲精品果冻| 国内毛片毛片毛片毛片毛片| 久久香蕉国产精品| 国产精品一及| 色综合亚洲欧美另类图片| 人人妻,人人澡人人爽秒播| 每晚都被弄得嗷嗷叫到高潮| 亚洲精品在线美女| 午夜两性在线视频| 国产精品亚洲一级av第二区| 国产精品免费视频内射| 亚洲最大成人中文| 欧美 亚洲 国产 日韩一| 日韩欧美在线乱码| 看片在线看免费视频| 91老司机精品| 国内久久婷婷六月综合欲色啪| 久久草成人影院| 三级毛片av免费| 黄色片一级片一级黄色片| 国产成人av教育| av福利片在线| 两性夫妻黄色片| av福利片在线| 国产成人一区二区三区免费视频网站| 非洲黑人性xxxx精品又粗又长| 99热6这里只有精品| 黄色片一级片一级黄色片| 久久人妻av系列| 国产熟女xx| 九色国产91popny在线| 丰满人妻熟妇乱又伦精品不卡| aaaaa片日本免费| 亚洲欧美激情综合另类| 精品一区二区三区四区五区乱码| 一级作爱视频免费观看| 久99久视频精品免费| 狂野欧美白嫩少妇大欣赏| 亚洲人成伊人成综合网2020| 欧美丝袜亚洲另类 | 婷婷精品国产亚洲av| 777久久人妻少妇嫩草av网站| 亚洲专区国产一区二区| 动漫黄色视频在线观看| 国产一区二区三区视频了| 我的老师免费观看完整版| 亚洲电影在线观看av| 国产精品久久久久久久电影 | av超薄肉色丝袜交足视频| 又大又爽又粗| 久久精品成人免费网站| 99riav亚洲国产免费| 好男人在线观看高清免费视频| 青草久久国产| 欧美成狂野欧美在线观看| 国产精品美女特级片免费视频播放器 | 在线观看一区二区三区| 99re在线观看精品视频| 久久亚洲精品不卡| 美女黄网站色视频| 国产一区二区在线av高清观看| 国产一区二区三区在线臀色熟女| 亚洲一区二区三区不卡视频| 观看免费一级毛片| 国产激情偷乱视频一区二区| 久久精品亚洲精品国产色婷小说| 无限看片的www在线观看| 婷婷精品国产亚洲av| 精品国产亚洲在线| 老汉色∧v一级毛片| 亚洲精品中文字幕在线视频| 999久久久国产精品视频| 久久欧美精品欧美久久欧美| 国产在线观看jvid| 免费电影在线观看免费观看| 亚洲国产欧美人成| 免费观看人在逋| 母亲3免费完整高清在线观看| 俺也久久电影网| x7x7x7水蜜桃| 中出人妻视频一区二区| 欧美另类亚洲清纯唯美| 最新美女视频免费是黄的| 99精品在免费线老司机午夜| 一级毛片高清免费大全| 女人爽到高潮嗷嗷叫在线视频| 亚洲av五月六月丁香网| 国产亚洲精品久久久久久毛片| 麻豆久久精品国产亚洲av| 国产精品影院久久| 在线视频色国产色| 久久这里只有精品中国| 99热只有精品国产| 亚洲av电影在线进入| 亚洲av熟女| 中亚洲国语对白在线视频| 操出白浆在线播放| 成人三级做爰电影| 久久午夜综合久久蜜桃| 韩国av一区二区三区四区| av免费在线观看网站| 97碰自拍视频| 亚洲国产精品sss在线观看| 在线免费观看的www视频| av有码第一页| 久久亚洲真实| 亚洲人与动物交配视频| 成人三级做爰电影| 看免费av毛片| 成人高潮视频无遮挡免费网站| 不卡一级毛片| 国产在线观看jvid| 国产高清视频在线观看网站| 中文字幕熟女人妻在线| 国产亚洲av嫩草精品影院| 国产69精品久久久久777片 | 久久伊人香网站| 久久 成人 亚洲| 午夜两性在线视频| 少妇人妻一区二区三区视频| 男女床上黄色一级片免费看| 国产黄色小视频在线观看| 精品欧美国产一区二区三| 可以免费在线观看a视频的电影网站| 两个人看的免费小视频| 久久精品国产综合久久久| 熟女电影av网| 日韩欧美精品v在线| 九九热线精品视视频播放| 久久久国产成人免费| 欧美日韩亚洲国产一区二区在线观看| 成人一区二区视频在线观看| 老司机在亚洲福利影院| 999久久久国产精品视频| 久久这里只有精品中国| 听说在线观看完整版免费高清| cao死你这个sao货| 热99re8久久精品国产| 国产久久久一区二区三区| 午夜日韩欧美国产| 国产亚洲精品久久久久久毛片| 久久久国产欧美日韩av| 亚洲熟妇熟女久久| 国模一区二区三区四区视频 | 国产97色在线日韩免费| 看黄色毛片网站| 国产精品一区二区精品视频观看| 波多野结衣高清无吗| 国产私拍福利视频在线观看| 舔av片在线| 日本一二三区视频观看| 老司机福利观看| 精品国内亚洲2022精品成人| 国产精品一区二区三区四区免费观看 | www国产在线视频色| 观看免费一级毛片| 日韩国内少妇激情av| 一进一出抽搐gif免费好疼| 色噜噜av男人的天堂激情| 国产一区二区三区在线臀色熟女| 男人的好看免费观看在线视频 | 国产av在哪里看| 亚洲熟妇中文字幕五十中出| 一个人免费在线观看电影 | 最近在线观看免费完整版| 精品久久蜜臀av无| 成人欧美大片| 免费在线观看影片大全网站| 亚洲专区中文字幕在线| 亚洲熟妇中文字幕五十中出| 欧美zozozo另类| e午夜精品久久久久久久| 91大片在线观看| 欧美不卡视频在线免费观看 | 在线观看日韩欧美| 中文字幕最新亚洲高清| 老熟妇乱子伦视频在线观看| av中文乱码字幕在线| 亚洲18禁久久av| 午夜免费激情av| 老司机福利观看| 国产亚洲精品综合一区在线观看 | 我要搜黄色片| 午夜免费激情av| 欧美日韩亚洲国产一区二区在线观看| 99热这里只有是精品50| 亚洲av五月六月丁香网| 亚洲九九香蕉| 亚洲人成网站高清观看| 性欧美人与动物交配| 男人的好看免费观看在线视频 | 搡老岳熟女国产| 久热爱精品视频在线9| 国产精品野战在线观看| 精品久久久久久成人av| 久久久国产成人免费| 51午夜福利影视在线观看| 叶爱在线成人免费视频播放| 在线观看美女被高潮喷水网站 | 18禁裸乳无遮挡免费网站照片| 午夜亚洲福利在线播放| 中亚洲国语对白在线视频| 亚洲九九香蕉| 日本 欧美在线| 亚洲一码二码三码区别大吗| 亚洲七黄色美女视频| 亚洲九九香蕉| 国产精品精品国产色婷婷| 国产精品日韩av在线免费观看| 十八禁网站免费在线| 久久精品国产亚洲av香蕉五月| 99re在线观看精品视频| 色综合亚洲欧美另类图片| 两个人免费观看高清视频| 亚洲国产看品久久| 久久精品aⅴ一区二区三区四区| 久久99热这里只有精品18| 久久精品国产亚洲av香蕉五月| 黄色女人牲交| 免费电影在线观看免费观看| 精品乱码久久久久久99久播| 日本精品一区二区三区蜜桃| 九色成人免费人妻av| 中文字幕人妻丝袜一区二区| 国产欧美日韩精品亚洲av| 亚洲成人国产一区在线观看| 丰满人妻一区二区三区视频av | 美女午夜性视频免费| 伊人久久大香线蕉亚洲五| 日韩欧美国产一区二区入口| 婷婷精品国产亚洲av在线| 亚洲专区中文字幕在线| 欧美av亚洲av综合av国产av| 人人妻,人人澡人人爽秒播| 18禁观看日本| 伊人久久大香线蕉亚洲五| 啦啦啦免费观看视频1| 午夜福利欧美成人| 日韩免费av在线播放| 午夜视频精品福利| 人人妻人人澡欧美一区二区| 12—13女人毛片做爰片一| 少妇粗大呻吟视频| 国产男靠女视频免费网站| 国产成人系列免费观看| 国产蜜桃级精品一区二区三区| 国产又色又爽无遮挡免费看| 精品国产美女av久久久久小说| 老熟妇仑乱视频hdxx| 777久久人妻少妇嫩草av网站| 欧美日韩精品网址| 国产精品亚洲美女久久久| 真人做人爱边吃奶动态| 欧美国产日韩亚洲一区| 国产激情久久老熟女| 欧美日韩亚洲国产一区二区在线观看| 精品日产1卡2卡| 久久热在线av| 一级毛片精品| 欧美乱码精品一区二区三区| 成人高潮视频无遮挡免费网站| 久久久久国产精品人妻aⅴ院| 日本黄色视频三级网站网址| 久久婷婷成人综合色麻豆| 18禁观看日本| 日韩精品免费视频一区二区三区| 国产午夜精品久久久久久| 久久天躁狠狠躁夜夜2o2o| 夜夜夜夜夜久久久久| 99久久99久久久精品蜜桃| 黄色 视频免费看| 在线永久观看黄色视频| 亚洲aⅴ乱码一区二区在线播放 | 国产精品久久久久久久电影 | 成人av在线播放网站| 天堂影院成人在线观看| 国语自产精品视频在线第100页| 天天躁狠狠躁夜夜躁狠狠躁| 中文字幕最新亚洲高清| 99精品在免费线老司机午夜| 国产午夜福利久久久久久| 国内揄拍国产精品人妻在线| 男女之事视频高清在线观看| 午夜老司机福利片| 50天的宝宝边吃奶边哭怎么回事| 亚洲欧美精品综合一区二区三区| 午夜影院日韩av| 亚洲精品粉嫩美女一区| 后天国语完整版免费观看| 欧洲精品卡2卡3卡4卡5卡区| 国产伦一二天堂av在线观看| 搡老岳熟女国产| 久久久久久久精品吃奶| 最新在线观看一区二区三区| 午夜精品一区二区三区免费看| 国语自产精品视频在线第100页| 丁香欧美五月| 淫秽高清视频在线观看| 国产成人aa在线观看| 欧洲精品卡2卡3卡4卡5卡区| 超碰成人久久| 搡老岳熟女国产| 搡老妇女老女人老熟妇| 国产日本99.免费观看| 日韩大尺度精品在线看网址| 精品一区二区三区视频在线观看免费| 精品国产美女av久久久久小说| 国产精品 国内视频| www.精华液| 亚洲精品一卡2卡三卡4卡5卡| 日韩 欧美 亚洲 中文字幕| 搡老妇女老女人老熟妇| 中出人妻视频一区二区| 搞女人的毛片| 巨乳人妻的诱惑在线观看| 日本a在线网址| 在线观看日韩欧美| 中文字幕av在线有码专区| 亚洲 国产 在线| 一个人免费在线观看的高清视频| 一进一出抽搐动态| 午夜精品一区二区三区免费看| 动漫黄色视频在线观看| 男女床上黄色一级片免费看| 日本一二三区视频观看| 日韩大尺度精品在线看网址| 国产精品综合久久久久久久免费| 久久香蕉国产精品| 成人国语在线视频| 国内精品一区二区在线观看| 国内揄拍国产精品人妻在线| 这个男人来自地球电影免费观看| 午夜精品一区二区三区免费看| 亚洲精品在线美女| 久久久水蜜桃国产精品网| 中文字幕精品亚洲无线码一区| 成年版毛片免费区| 国产亚洲欧美在线一区二区| 两性夫妻黄色片| 亚洲av成人精品一区久久| 欧美精品亚洲一区二区| 美女高潮喷水抽搐中文字幕| 男人的好看免费观看在线视频 | 久久99热这里只有精品18| 一边摸一边抽搐一进一小说| 亚洲人成网站高清观看| 亚洲av成人一区二区三| 身体一侧抽搐| 亚洲精品粉嫩美女一区| 又爽又黄无遮挡网站| 手机成人av网站| 99精品欧美一区二区三区四区| 亚洲欧美日韩高清专用| 搞女人的毛片| 免费av毛片视频| 日韩有码中文字幕| 国产伦一二天堂av在线观看| 国内揄拍国产精品人妻在线| 成年人黄色毛片网站| 看黄色毛片网站| 巨乳人妻的诱惑在线观看| 18美女黄网站色大片免费观看| 亚洲天堂国产精品一区在线| 动漫黄色视频在线观看| 舔av片在线| 色综合欧美亚洲国产小说| 亚洲专区国产一区二区| 日本精品一区二区三区蜜桃| 中文字幕精品亚洲无线码一区| 成人永久免费在线观看视频| 成人三级黄色视频| 母亲3免费完整高清在线观看| 久久国产精品人妻蜜桃| 999精品在线视频| 亚洲av电影在线进入| 亚洲人成伊人成综合网2020| 久久久久国产精品人妻aⅴ院| 亚洲成人国产一区在线观看| 欧美日韩福利视频一区二区| 一本综合久久免费| 在线永久观看黄色视频| 欧美人与性动交α欧美精品济南到| 搡老熟女国产l中国老女人| 久久精品国产亚洲av香蕉五月| 亚洲一卡2卡3卡4卡5卡精品中文| 看黄色毛片网站| 久久亚洲精品不卡| 1024手机看黄色片| 国产亚洲精品一区二区www| 国产又色又爽无遮挡免费看| 精品欧美国产一区二区三| 99热这里只有精品一区 | 国产麻豆成人av免费视频| 免费一级毛片在线播放高清视频| 亚洲成人中文字幕在线播放| 亚洲免费av在线视频| 人人妻人人澡欧美一区二区| 亚洲欧美激情综合另类| 国语自产精品视频在线第100页| 亚洲成人国产一区在线观看| 非洲黑人性xxxx精品又粗又长| 婷婷亚洲欧美| 久久久国产精品麻豆| 在线播放国产精品三级| 悠悠久久av| 搡老妇女老女人老熟妇| 人妻丰满熟妇av一区二区三区| 国产在线观看jvid| 久久九九热精品免费| 又黄又粗又硬又大视频| 国内揄拍国产精品人妻在线| 欧美人与性动交α欧美精品济南到| 欧美绝顶高潮抽搐喷水| 亚洲精品色激情综合| 国产97色在线日韩免费| 欧美成人午夜精品| 免费观看人在逋| 高潮久久久久久久久久久不卡| 日韩欧美精品v在线| 午夜福利视频1000在线观看| 国产亚洲精品综合一区在线观看 | 欧美丝袜亚洲另类 | 亚洲性夜色夜夜综合| 最新美女视频免费是黄的| 神马国产精品三级电影在线观看 | 又黄又粗又硬又大视频| 中文字幕人妻丝袜一区二区| 成熟少妇高潮喷水视频| 伊人久久大香线蕉亚洲五| 久久性视频一级片| 久久 成人 亚洲| 天天躁狠狠躁夜夜躁狠狠躁| 免费人成视频x8x8入口观看| 成人av在线播放网站| 日本撒尿小便嘘嘘汇集6| 亚洲精品久久国产高清桃花| 国产麻豆成人av免费视频| 精品欧美一区二区三区在线| 老司机午夜十八禁免费视频| 久久久精品国产亚洲av高清涩受| 国产精品 国内视频| 成人18禁高潮啪啪吃奶动态图| 每晚都被弄得嗷嗷叫到高潮| 国产伦人伦偷精品视频| 国产成人av激情在线播放| 97碰自拍视频| tocl精华| 久久国产精品影院| 少妇裸体淫交视频免费看高清 | 手机成人av网站| 视频区欧美日本亚洲| 日韩欧美国产在线观看| 亚洲成人中文字幕在线播放| 国产成人欧美在线观看| 一级a爱片免费观看的视频| 久久午夜亚洲精品久久| 老司机深夜福利视频在线观看| 国产一区二区在线av高清观看| 日韩欧美国产在线观看| 亚洲成人中文字幕在线播放| 三级毛片av免费| 日本黄大片高清| 午夜免费激情av| 白带黄色成豆腐渣| 男女之事视频高清在线观看| 中文字幕高清在线视频| 在线免费观看的www视频| 国产激情久久老熟女| 天天躁狠狠躁夜夜躁狠狠躁| 三级毛片av免费| 成人av一区二区三区在线看| 中国美女看黄片| 久久久久国产精品人妻aⅴ院| 露出奶头的视频| 黄色毛片三级朝国网站| 美女高潮喷水抽搐中文字幕| www.精华液| 亚洲国产看品久久| 少妇的丰满在线观看| 亚洲乱码一区二区免费版| 久久久精品国产亚洲av高清涩受| 老司机靠b影院| 制服诱惑二区| 午夜两性在线视频| 18美女黄网站色大片免费观看| 国产精品一区二区三区四区免费观看 | 色av中文字幕| 波多野结衣高清无吗| 一级作爱视频免费观看| 亚洲精品在线美女| 青草久久国产| 在线观看www视频免费| 国产亚洲av嫩草精品影院| 国产视频一区二区在线看| 男女视频在线观看网站免费 | 亚洲精品美女久久久久99蜜臀| 久久人妻av系列| 亚洲美女视频黄频| 久久伊人香网站| 丰满的人妻完整版| 级片在线观看| 99热只有精品国产| 国内精品久久久久精免费| www.999成人在线观看| 亚洲欧美日韩高清在线视频| 亚洲精品美女久久av网站| 成人一区二区视频在线观看| 亚洲,欧美精品.| 黄色a级毛片大全视频| 天堂动漫精品| 怎么达到女性高潮| 国产黄a三级三级三级人| 亚洲av中文字字幕乱码综合| 久久久久久大精品| 好看av亚洲va欧美ⅴa在| 久久人妻福利社区极品人妻图片| 搞女人的毛片| 大型av网站在线播放| 变态另类成人亚洲欧美熟女| 久久精品91无色码中文字幕| 久久香蕉精品热| 18禁裸乳无遮挡免费网站照片| 久久久久久免费高清国产稀缺|