A Double Network Hydrogel with High Mechanical Strength and Shape Memory Properties

Double network(DN)hydrogels as one kind of tough gels have attracted extensive at-tention for their potential applications in biomedical and load-bearing fields.Herein,we import more functions like shape memory into the conventional tough DN hydro-gel system.We synthesize the PEG-PDAC/P(AAm-co-AAc)DN hydrogels,of which the first network is a well-defined PEG(polyethylene glycol)network loaded with PDAC(poly(acryloyloxyethyltrimethyl ammonium chloride))strands,while the second network is formed by copolymerizing AAm(acrylamide)with AAc(acrylic acid)and cross-linker MBAA(N;N′-methylenebisacrylamide).The PEG-PDAC/P(AAm-co-AAc)DN gels exhibits high mechanical strength.The fracture stress and toughness of the DN gels reach up to 0.9 MPa and 3.8 MJ/m^3,respectively.Compared with the conventional double network hydrogels with neutral polymers as the soft and ductile second network,the PEG-PDAC/P(AAm-co-AAc)DN hydrogels use P(AAm-co-AAc),a weak polyelectrolyte,as the second network.The AAc units serve as the coordination points with Fe^3+ions and physically crosslink the second network,which realizes the shape memory property activated by the reducing ability of ascorbic acid.Our results indicate that the high mechanical strength and shape memory properties,probably the two most important characters related to the potential application of the hydrogels,can be introduced simultaneously into the DN hydrogels if the functional monomer has been integrated into the network of DN hydrogels smartly.

Effect of β-Cyclodextrin Upon the Sol-gel Transition of Methylcellulose Solutions in the Presence of Sodium Dodecyl Sulfate

methylcellulose ( MC )的大音阶的第五音胶化转变温度答案面对象 SDS 和 -cyclodextrin 的混合物一样的钠 dodecyl 硫酸盐( SDS )(-CD)被测量，并且二个竞争相互作用的效果，在 SDS 和 MC 之间的恐水病的相互作用和在在 MC 答案的大音阶的第五音胶化转变之上的 SDS 和-CD,之间的包括相互作用被学习。在 SDS 和 CD 之间的包括相互作用比在 SDS 和 MC 之间的恐水病的相互作用大得多，这被发现了。作为结果，在 SDS 和 -CD, 的共存， MC 答案的大音阶的第五音胶化转变温度把一样的值放在，独立于在解决方案的 SDS 的集中在 SDS 的集中是不到 CD 条件下。我们的试验性的结果不仅建议在 MC 答案的大音阶的第五音胶化转变之上的 SDS 的效果能被 CD 完全屏蔽而且显示到 CD 的 SDS 的包括比率能是由使用 rheological 测量的坚定的份量上。到 CD 的 SDS 的包括比率是 1:1 ，它 poly 在对到 CD 的 SDS 的包括比率的好同意面对( vincyl pyrrolidone )由粘性测量决定了但是面对由使用 rheological 测量的相对地控告的聚合电解质与到 CD 的 SDS 的包括比率极其不同，主要由于在 SDS 和 MC 之间的相互作用的机制与在 SDS

Monte Carlo Study on Spontaneous Recoil of Confined DNA Chain

长 DNA 链的部分被一个电场驾驶进限制环境，当剩余的留在高熵的区域时。在这个领域的移动之上，链自发地撤退到高熵的区域。这个动态过程被蒙特卡罗模拟调查。模拟复制 DNA 链的 recoil 是开始慢的并且逐渐地由于 confinement-entropic 力量的存在处于速度增加的试验性地观察的现象。结果与增加尺寸或减少显示出那 DNA 链的 recoil 速度将增加的 nanopillars 的间距。进一步的分析建议典型的熵与在监禁的免费部分的区域部分每在监禁的单体成正比。

INTERMOLECULAR AND INTRAMOLECULAR INTERACTIONS OF POLYMER GUAR GUM IN SOLUTIONS

The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases due to the formation of crosslinks. As a result, the polymer chains of guar gum in solution shrink in size and the reduced viscosity of polymer solution decreases accordingly. On the other hand, if the concentration of guar gum is greater than 0.045 g/dL, the intermolecular interaction becomes apparent due to the same reason. The polymer chains, therefore, associate together and the reduced viscosity of polymer solution increases considerably. According to this technique, the critical concentration c^＊, presented by de-Gennes, is determined successfully.

Rhodamine Mechanophore Functionalized Mechanochromic Double Network Hydrogels with High Sensitivity to Stress

Mechanochromic hydrogels, a new class of stimuli-responsive soft materials, have potential applications in a number of fields such as damage reporting and stress/strain sensing. We prepared a novel mechanochromic hydrogel using a strategy that has been developed to prepare dual-network(DN) hydrogels. A hydrophobic rhodamine derivative(Rh mechanophore) was covalently incorporated into a first network as a cross-linker. This first network embedded with Rh mechanophore within the DN hydrogel was pre-stretched. This guaranteed that the stress could be transferred extensively to the Rh-crosslinked first network once the hydrogel was under an applied force. Interestingly, we found that the threshold stress required to activate the mechanochromism of the hydrogel was less than 200 kPa, and much less than those in previous reports. Moreover, because of the excellent sensitivity of the hydrogel to stress, the DN hydrogel exhibited reversible freezing-induced mechanochromism. Benefiting from the sensitivity of Rh mechanophore to both p H and force, the DN hydrogel showed p H-regulated mechanochromic behavior. Our experimental results indicate that the preparation strategy we used introduces sensitive mechanochromism into the hydrogel and preserves the advantageous mechanical properties of the DN hydrogel. These results will be beneficial to the design and preparation of mechanochromic hydrogels with high stress sensitivity, and foster their practical applications in a number of fields such as damage reporting and stress/strain sensing.