Facile synthesis of chromium chloride/poly(methyl methacrylate) core/shell nanocapsules by inverse miniemulsion evaporation method and application as delayed crosslinker in secondary oil recovery

Cr(III)ehydrolyzed polyacrylamide(HPAM)gels have been extensively studied as a promising strategy controlling waste water production for mature oilfields.However,the gelation time of the current technologies is not long enough for in-depth placement.In this study,we report a novel synthesis method to obtain chromium chloride/poly(methyl methacrylate)(PMMA)nanocapsules which can significantly delay the gelation of HPAM through encapsulating the chromium chloride crosslinker.The chromium chloride-loaded nanocapsules(CreNC)are prepared via a facile inverse miniemulsion evaporation method during which the hydrophobic PMMA polymers,pre-dispersed in an organic solvent,were carefully controlled to precipitate onto stable aqueous miniemulsion droplets.The stable aqueous nanodroplets(W)containing Cr(III)are dispersed in a mixture of organic solvent(O1)with PMMA and nonsolvent medium(O2)to prepare an inverse miniemulsion.With the evaporation of the O1,PMMA forms CreNCs around the aqueous droplets.The CreNCs are readily transferred into water from the organic nonsolvent phase.The CreNCs exhibit the tunable size(358-983 nm),Cr loading(7.1%-19.1%),and Cr entrapment efficiency(11.7%-80.2%),with tunable zeta potentials in different PVA solutions.The CreNCs can delay release of Cr(III)and prolong the gelation time of HPAM up to 27 days.

CURING KINETICS AND PROPERTIES OF ACRYLIC RESIN CURED WITH AZIRIDINE CROSSLINKER

A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinking properties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in the emulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transition temperature (T.) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kinetics studied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low (65.1 kJ/mol). These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and can be used at room temperature.

Physical mechanism of the compressive response of F-actin networks:significance of crosslinker unbinding events

A model of crosslinker unbinding is implemented in a highly coarse- grained granular model of F-actin cytoskeleton. We employ this specific granular model to study the mechanisms of the compressive responses of F-actin networks. It is found that the compressive response of F-actin cytoskeleton has dependency on the strain rate. The evolution of deformation energy in the network indicates that crosslinker unbinding events can induce the remodelling of F-actin cytoskele- ton in response to external loadings. The internal stress in F-actin cytoskeleton can efficiently dissipate with the help of crosslinker unbinding, which could lead to the soontaneous relaxation of living cells.

Polyamine-Polymeric Micelle Hybrid Hydrogel: Microscopic Properties of Crosslinkers Affecting Macroscopic Rheological Properties of Hydrogel

We have developed a hybrid hydrogel that is formed from a crosslinkable polymeric micelle and a polyamine. Under optimal conditions, the hydrogel rapidly formed in one second after a crosslinkable polymeric micelle solution was mixed with a polyamine solution. We could change the hydrogel’s gelation properties, such as the storage modulus and gelation time by tuning the molecular weights of block copolymers and by tuning the pH of the dissolving-solvent of the hydrogel’s constituent components. Furthermore, we have clarified here that the structural difference among the micelles acting as crosslinkers can affect the gelation properties of the hydrogel. According to our findings, the hydrogel that was formed from the polymeric micelles possessing a highly packed (i.e., well-entangled or crosslinked) inner core exhibited a higher storage modulus than the hydrogel that was formed from the polymeric micelles possessing a lowly packed structure. Our results demonstrate that a microscopic structural difference among crosslinkers can induce a macroscopic change in the properties of the resulting hydrogels. For medical applications, the hydrogel proposed in the present paper can encapsulate the hydrophobic compounds in crosslinkers (polymeric micelles) so that the hydrogel can be available as the biomaterial for their sustained release.

Detecting early changes in choroidal vascularity and thickness using optical coherence tomography in patients with corneal crosslinking for keratoconus

AIM:To investigate changes in choroidal thickness and vascularity in keratoconus patients treated with corneal crosslinking.METHODS:This study evaluated 28 eyes of 22 patients with keratoconus who underwent corneal crosslinking.The choroidal thicknesses were evaluated on enhanced depth imaging optical coherence tomography at the preoperative and postoperative 3d,1,and 3mo.Choroidal thickness in the four cardinal quadrants and the fovea were evaluated.The choroidal vascularity index was also calculated.RESULTS:There was no significant difference in central choroidal thickness between the preoperative and postoperative 3d,1mo(P>0.05).There was a significant increase in the 3mo(P=0.034)and a significant decrease in the horizontal choroidal vascularity index on the postoperative 3d(P=0.014),there was no statistically significant change in vertical axes and other visits in horizontal sections(P>0.05).CONCLUSION:This study sheds light on choroidal changes in postoperative corneal crosslinking for keratoconus.While it suggests the procedure’s relative safety for submacular choroid,more extensive research is necessary to confirm these findings and their clinical significance.

Stromal lenticule addition keratoplasty with corneal crosslinking for corneal ectasia secondary to FS-LASIK:a case series

●AIM:To explore the clinical efficacy and safety of stromal lenticule addition keratoplasty(SLAK)with corneal crosslinking(CXL)on patients with corneal ectasia secondary to femtosecond laser-assisted in situ keratomileusis(FS-LASIK).●METHODS:A series of 5 patients undertaking SLAK with CXL for the treatment of corneal ectasia secondary to FS-LASIK were followed for 4-9mo.The lenticules were collected from patients undertaking small incision lenticule extraction(SMILE)for the correction of myopia.Adding a stromal lenticule was aimed at improving the corneal thickness for the safe application of crosslinking and compensating for the thin cornea to improve its mechanical strength.●RESULTS:All surgeries were conducted successfully with no significant complications.Their best corrected visual acuity(BCVA)ranged from 0.05 to 0.8-2 before surgery.The pre-operational total corneal thickness ranged from 345-404μm and maximum keratometry(Kmax)ranged from 50.8 to 86.3.After the combination surgery,both the corneal keratometry(range 55.9 to 92.8)and total corneal thickness(range 413-482μm)significantly increased.Four out of 5 patients had improvement of corneal biomechanical parameters(reflected by stiffness parameter A1 in Corvis ST).However,3 patients showed decreased BCVA after surgery due to the development of irregular astigmatism and transient haze.Despite the onset of corneal edema right after SLAK,the corneal topography and thickness generally stabilized after 3mo.●CONCLUSION:SLAK with CXL is a potentially beneficial and safe therapy for advanced corneal ectasia.Future work needs to address the poor predictability of corneal refractometry and compare the outcomes of different surgical modes.

修正硫化效应法制定厚制品橡胶硫化时间

测试了混炼胶不同温度下的硫化曲线,研究了硫化温度对不同混炼胶交联程度的影响;以天然橡胶(NR)/顺丁橡胶(BR)硫化胶为研究对象,进一步测试了其不同硫化温度下的硫化曲线,进行硫化程度修正系数P和硫化温度系数K拟合,采用预埋热电偶法测试了厚制品橡胶中心处的升温曲线,采用修正以及传统硫化效应法分别进行二者工程硫化时间计算。结果表明,硫化温度对不同橡胶硫化程度会产生较大影响,采用修正硫化效应法硫化的厚制品与标准试片更加接近,而传统硫化效应法硫化程度偏低。

可逆双交联网络自修复聚氨酯的制备与性能研究

通过物理交联法制备一系列由可逆双硫键聚合物单交联网络和可逆-Fe^(3+)配位键聚合物单交联网络组成的双交联网络聚氨酯弹性体,得到可逆双交联网络互锁自修复聚氨酯材料(FSN)。该材料利用可逆双键网络中的二硫键和Fe^(3+)配位键网中的金属配位键互穿互锁,形成两个单交联网络协同的可逆双交联网络自修复弹性体材料。研究了双交联网络的自修复能力和力学性能,实验结果表明,FSN网络的机械应力达到3.5 MPa;聚合物自修复效率高达80%以上。该结果证明两个单交联网络间存在协同作用,使得FSN比单一可逆聚合物网络在力学性能和自修复能力方面均有显著提升。

共交联VMQ/POE共混物的热致形状记忆行为研究

将甲基乙烯基硅橡胶(VMQ)与乙烯-辛烯共聚物(POE)进行机械共混和化学交联,制得具有热响应形状记忆特性的共交联VMQ/POE共混物,其形状记忆性能由交联、结晶、熔融所决定,其中交联程度对结晶和熔融有显著的影响。将着重分析交联剂对共混物的硫化特性以及热学、拉伸和弯曲形状记忆性能的影响规律。结果表明:添加交联剂的共混物胶料的硫化曲线呈现出焦烧、热硫化、平坦硫化等典型硫化特征,且胶料的交联速率和凝胶率均随交联剂用量增加而呈现增大的趋势。在相同的拉伸应力载荷下,随着交联剂用量的增加,共混物的最大应变值和固定率逐渐减小,而回复率先增大后减小;共混物的循环拉伸形状记忆稳定性较好,最大应变和固定率变化较小,而回复率有明显的增大。在相同的弯曲应力作用下,共混物的固定角度、回复角度、回复速度均随交联剂用量增加而呈现出增大的趋势。对比发现,当交联剂添加份数为0.5~1.0内,共混物具有较为理想的拉伸和弯曲形状记忆性能。

基于醛-胺席夫碱反应制备的葡聚糖水凝胶的结构和性能

采用高碘酸钠对葡聚糖进行氧化,制备了氧化葡聚糖(Dex-CHO),Dex-CHO与胱胺二盐酸盐(CYS)发生醛-胺席夫碱交联反应制备了一系列葡聚糖水凝胶。采用1HNMR和FTIR对其进行了结构确认,通过SEM和荧光光谱考察了Dex-CHO中的醛基和CYS中的氨基的物质的量之比(简称醛氨比,下同)、葡聚糖重均相对分子质量(M_(w))、Dex-CHO质量浓度对葡聚糖水凝胶凝胶化时间、微观结构、溶胀性能及流变性能的影响。结果表明,葡聚糖水凝胶具有经典三维多孔结构和良好荧光性质,当葡聚糖Mw为40000、Dex-CHO质量浓度为0.0750 g/mL、醛氨比为1.49∶1时,制备的葡聚糖水凝胶具有更优良的三维网状结构(凝胶化时间2.5 min)、黏弹性能(弹性模量为165 kPa,黏性模量为12 kPa)及溶胀性能(30 min的溶胀率为5.9 g/g)。此外,酸敏感席夫碱键及还原敏感裂解二硫键使葡聚糖水凝胶的降解行为具有明显的pH和还原双敏感性。

载氨基吸附材料制备及其分离锌离子的研究

以亚氨基二乙酸螯合树脂(CH90)为基体,利用聚多巴胺(PDA)作为交联剂,将聚乙烯亚胺(PEI)接枝到基体表面上,制备了一种对锌离子同时具有高吸附和易再生特点的新型改性树脂(CH90-PDA-PEI),并对其进行了一系列的表征和测试。结果表明,与传统的阴离子交换树脂(717)相比,在278 K时,CH90-PDA-PEI对Zn(Ⅱ)的最大吸附量为160.4 mg/g,选择性分离因子为159.31。在使用实际钢厂废水进行动态吸附测试时,CH90-PDA-PEI的吸附性能相比717树脂提升了26.9%,而再生时用水量减少了6.7%,且在循环测试时可以保持稳定的性能。

超高速冲击下石墨烯增强环氧树脂的分子动力学模拟

为了研究超高速冲击作用下防护材料的动态损伤与破坏机理,首先构建了以刚性球形金刚石为弹丸、上层为单层石墨烯、下层为环氧树脂的分子模型(防护模型),其中环氧树脂分子模型由双酚A型环氧树脂和胺类固化剂4,4-二氨基二苯砜通过Perl脚本在MaterialsStudio软件中构建完成。然后采用分子动力学模拟方法从微观角度研究了刚性球形金刚石弹丸以不同的超高速(10,20,30,40,50km/s和60km/s)冲击防护模型的过程,分析了冲击过程中防护模型结构、能量、动态损伤与破坏行为的变化情况。研究结果表明,弹丸侵入防护模型后,受到防护模型的阻碍,速度急速下降,初始速度越大,受到的阻力越大,速度下降的越快;在弹丸的高速冲击作用下,防护模型会形成空洞,侵入速度越大,空洞面积越大,势能变化量越大,同时石墨烯和环氧树脂中的部分化学键会发生断裂。当弹丸速度较小时,弹丸滞留在防护模型中,动能损耗接近100%,当弹丸速度为40,50,60km/s时,动能损耗率分别为98.32%,92.51%和61.65%。

3D打印中空管道双交联水凝胶组织工程支架

背景:在培养对结构、氧需求度较高的细胞时,需要构建一个具有中空管道结构的立体生物支架来保证细胞得到足够的营养与氧气。近年来,具有中空管道结构的水凝胶组织工程支架受到广泛关注。目的:以海藻酸钠为基础的生物支架材料结合同轴打印技术制备具有中空管道结构的组织工程支架,通过灌注方式接种细胞验证其生物相容性。方法:制备海藻酸钠-丙烯酰胺混合打印溶液,控制同轴打印过程中的内外层打印速度、海藻酸钠浓度、接收皿中氯化钙浓度等参数实现打印具有中空管道组织工程支架——海藻酸钠-聚丙烯酰胺双交联水凝胶,表征支架的微观形貌与弹性模量;将小鼠成纤维细胞灌注至组织工程支架中空管道内,利用活死细胞染色观察支架的细胞相容性。结果与结论:①通过探究打印过程中的打印参数,当内层打印速度不变时,中空管道的外径随着外层打印溶液的流速提升而提升,内径有略微提升;当外层打印溶液流速不变、内层溶液流速提升时,中空管道支架的外径基本不变,内径有明显提升;②实验结果显示海藻酸钠的最佳浓度为2.5%,过高的浓度不利于多层结构层与层之间的融合,过低的浓度制备出的水凝胶机械性能不足;③海藻酸钠-聚丙烯酰胺双交联水凝胶的弹性模量较高,普遍高于200 kPa,并且随着氯化钙浓度的提升而增大,在内层氯化钙浓度为2%、接收皿氯化钙浓度为0.3%时双交联水凝胶的弹性模量达到最大值(375 kPa);④组织工程支架灌注细胞体外培养后的活死细胞染色显示,细胞沿着中空管道轴向分布且具有较高的存活率,但细胞浓度小于灌注时的细胞浓度;⑤结果表明,海藻酸钠-聚丙烯酰胺双交联水凝胶具有较强的机械性能与良好的生物相容性,可应用在构建具有中空管道的组织工程支架中,并且“先制备支架、后接种细胞”的方式也避免了传统“细胞与打印溶液混合再进行制备”方式对支架材料及加工方式的限制。

基于压缩应力表征透明质酸钠交联反应进程方法

背景:目前,凝胶交联反应进程可通过核磁检测等方法测定交联度来表征,也可以采用流变仪监测交联固化过程中黏弹性行为的变化来表征,但这些方法操作复杂且会破坏样品,急需建立一种操作简单、测定时不用特殊制样、不会破坏样品的交联反应进程监控方法。目的:建立一种表征透明质酸钠交联反应进程的方法。方法:采用1,4-丁二醇二缩水甘油醚作为交联剂,选择不同交联度(1%,2%,3%和4%)、不同透明质酸钠分子质量(400,700,1500和3000 kD)、不同氢氧化钠溶液浓度(1%,2%和3%)和不同反应温度(4,25,37和50℃)这4个因素来制备透明质酸钠凝胶。利用电子万能拉力试验机测定交联凝胶被下压形变1 mm时的压缩应力,根据压缩应力变化情况来监控交联进程,进而判断交联反应充分性及交联工艺对交联进程的影响。结果与结论:①交联时间延长,凝胶硬度增强,压缩应力增加,达到一定值后,透明质酸钠交联结构在强碱作用下发生降解,凝胶硬度减小,压缩应力下降,因此可以根据压缩应力的大小表征凝胶的软硬程度,通过压缩应力与交联时间绘制曲线来表征交联反应进程。根据压缩应力变化情况可知,交联反应温度对交联反应时间及凝胶的硬度有着明显影响,其他反应因素(交联度、交联时碱浓度、透明质酸钠分子质量)对反应时间无明显影响,但是对凝胶硬度有着较大的影响。②根据CORREL函数处理结果表明,随着交联时间的变化,压缩应力与弹性模量和动力黏度的变化趋势一致,均可以用来表征透明质酸钠凝胶的交联进程。③基于交联凝胶压缩应力不仅能表征交联反应进程,还能初步判定凝胶软硬程度,该方法能够进行实时、原位检测,具有操作简单、不会破坏样品等优点,为透明质酸钠及其他物质交联反应进程监控提供了一种解决办法和新的思路。

交联透明质酸钠凝胶对近距离放射治疗中危及器官的隔离防护作用

背景:交联透明质酸钠凝胶具备良好的力学性能、生物相容性与降解性,可作为肿瘤放射治疗中的隔离防护材料,用于保护危及器官免受多余辐照剂量的损伤。目的:探究交联透明质酸钠凝胶在近距离放射治疗中减少危及器官受照剂量等方面的安全性及有效性。方法:取周龄相同、体质量相近的无特定病原体级昆明小鼠作为实验对象,共16只,采用随机数字表法分为实验组与对照组,每组8只。在实验组小鼠背部皮下植入125Ⅰ放射性粒子,随后环绕放射性粒子周边注射交联透明质酸钠凝胶,在对照组小鼠背部皮下仅植入125Ⅰ放射性粒子。注射完成后,采用螺旋CT扫描测量放射性粒子与表皮的距离,采用辐射剂量仪检测体表辐射剂量;注射后10周内,观察小鼠生长状态及存活率、皮肤放射损伤情况及凝胶存留量。结果与结论:①螺旋CT扫描显示植入的凝胶相对集中,并且使放射性粒子与表皮之间产生有效的间隔距离。实验组小鼠体表辐射剂量明显低于对照组(P<0.01)。②在实验观察期内,两组小鼠均存活,对照组小鼠在实验观察后期出现明显烦躁等不稳定表现,部分实验组小鼠出现类似行为;两组小鼠日摄食量无明显变化,体质量呈现相同的增长趋势。植入放射性粒子后两组小鼠均出现不同程度的放射性皮肤损伤,自注射后第23天开始至实验结束,实验组小鼠皮肤放射损伤评分均低于对照组(P<0.01)。植入后第10周,实验组6只小鼠皮下无明显凝胶残留,2只小鼠皮下存在极少量散在的凝胶状样品。③结果表明,注射交联透明质酸钠凝胶可通过物理占位作用增加125Ⅰ放射性粒子放射靶区和靶外危及器官的间隔空间,有效降低危及器官的受照剂量,对危及器官起到隔离防护作用。

Metal cation crosslinking of Ti O_2-alginate hybrid gels

In order to improve the substrate diffusion properties and stability of an immobilized enzyme alginate microgels modified with TiO2 nanoparticles were employed as the enzyme immobilizing support.Ionotropic gelation was applied for the preparation of hybrid gels while Ca2＋ Ce3＋ Ni2＋Cu2＋and Fe3＋were employed as the crosslinkers.Papain was selected as the model enzyme. UV-Vis spectroscopy was employed to investigate the activity of papain to evaluate kinetics and stability.Analysis results show that the highest affinity the lowest Michaelis-Menten constant Km =11.0 mg/mL and the highest stability are obtained when using Cu2＋as the crosslinker.The effect of the mass ratio of TiO2 to papain on the stability and leakage of papain is also investigated and the results show that 10∶1 TiO2∶papain is optimal because the proper use of TiO2 can reduce enzyme leakage and ensure enzyme stability.Preparing Cu/alginate/TiO2 hybrid gels via ionotropic gelation can provide a satisfactory diffusion capability and enzyme stability.

微交联对热塑性聚氨酯弹性体耐磨性的影响

采用己二酸丁二醇酯多元醇(PBA)、4,4'–二苯基甲烷二异氰酸酯(MDI)、1,4–丁二醇(BDO)为原料合成热塑性聚氨酯弹性体(TPUE)。采用不同方式对TPUE进行微交联改性,研究了不同交联方式对TPUE耐磨性的影响。结果表明,当聚酯多元醇官能度为2.003、三羟甲基丙烷与总扩链剂质量比为5%时,TPUE耐磨性最佳,添加液化MDI对TPUE耐磨性无明显提升。

Study on Tribological Properties of Irradiated Crosslinking UHMWPE Nano-Composite

Ultra High Molecular Weight Polyethylene(UHMWPE)has been widely used as a bearing material for artificial joint replacement over forty years.It is usually crosslinked by gamma rays irradiation before its implantation into human body.In this study,UHMWPE and UHMWPE/nano-hydroxyapatite(n-HA)composite were prepared by vacuum hot-pressing method.The prepared materials were irradiated by gamma rays in vacuum and molten heat treated in vacuum just after irradiation.The effect of filling n-HA with gamma irradiation on tribological properties of UHMWPE was investigated by using friction and wear experimental machine(model MM-200)under deionized water lubrication.Micro-morphology of worn surface was observed by metallographic microscope.Contact angle and hardness of the materials were also measured.The results show that contact angle and hardness are changed by filling n-HA and gamma irradiation.Friction coefficient and wear rate under deionized water lubrication are reduced by filling n-HA.While friction coefficient is increased and wear rate is reduced significantly by gamma irradiation.The worn surface of unfilled material is mainly characterized as adhesive wear and abrasive wear,and that of n-HA filled material is mainly characterized as abrasive wear.After gamma irradiation,the degrees of adhesive and abrasive wear for unfilled material and abrasive wear of n-HA filled material are significantly reduced.Unfilled and filled materials after irradiation are mainly shown as slight fatigue wear.The results indicate that UHMWPE and UHMWPE/n-HA irradiated at the dose of 150 kGy can be used as bearing materials in artificial joints for its excellent wear resistance compared to original UHMWPE.

Procyanidins Inhibit Tumor Angiogenesis by Crosslinking Extracellular Matrix

Objective： Procyanidins （PC） are widely available natural polyphenols. The present study is designed to investigate if PC can inhibit angiogenesis in lung adenocarcinoma xenografts through crosslinking vascular extracellular matrix （ECM） and preventing proteolysis by matrix metalloproteinases （MMPs）. Methods： Using the in vitro MMP-2 proteolysis and in vivo subcutaneous implantation models, we investigated if PC crosslinking inhibits MMP-mediated proteolysis. Using a cultured cell detachment assay, an in vitro angiogenesis assay, and a cell proliferation assay, we investigated if PC inhibits MMP-2-mediated endothelial cell detachment, angiogenesis, and cell proliferation, respectively. Using tumor xenografts, we evaluated if PC can inhibit growth of lung adenocarcinoma. Results： PC crosslink vascular ECM proteins, protecting them against proteolysis by MMPs in vitro and in vivo, protecting cultured human umbilical vein endothelial cells from detachment by MMP-2, and inhibiting in vitro angiogenesis. However, PC （0.75-100 μg/mL） did not inhibit vascular and tumor cells proliferation. PC injections （30 mg PC/kg bodyweight） in situ had anticancer effects on xenografts of lung adenocarcinoma, most likely by inhibiting angiogenesis during ECM proteolysis by MMPs. Conclusion： The results suggest that PC may be important MMP inhibitors that can be used as therapeutic anticancer agents.

Crosslinked P84 copolyimide/MXene mixed matrix membrane with excellent solvent resistance and permselectivity

MXene is a novel 2D lamellar material with excellent hydrophilicity and permselectivity. MXene was introduced in the P84 polymer matrix and the matrix was crosslinked with triethylenetetramine(TETA) to improve the permselectivity and solvent resistance of the polyimide membrane. The membrane was characterized with SEM, AFM and ATR-FTIR, and effects of MXene content on the membrane morphology and separation performance are investigated. The membrane prepared with 18% P84 and 1% MXene shows high rejection(100%) to gentian violet(408) and high flux(268 L·m^-2·h^-1) at 0.1 MPa and ambient temperature. MXene endows the membrane with much water channel and denser functional layer which improves the membrane performance obviously. The membrane shows excellent solvent resistance to dimethylformamide(DMF), acetone and methanol after crosslinking with TETA during the 18 days of immersion.