新型羧甲基壳聚糖水凝胶的合成与表征

通过1-乙基-(3-二甲基氨基丙基)碳二亚胺盐酸盐(EDC)/N-羟基琥珀酰亚胺(NHS)催化体系使羧甲基壳聚糖(CMCS)交联,制备了新型羧甲基壳聚糖水凝胶.探讨了EDC用量和EDC/NHS质量比对水凝胶特性的影响.CMCS水凝胶具有pH响应特性,在等电位点溶胀率最小.降解实验结果表明,水凝胶浸泡在磷酸盐缓冲溶液中,10 d失重率在15%~45%之间,主要是未交联部分溶解所致.而浸泡在含有0.2 mg/mL溶菌酶的磷酸盐缓冲溶液中,低交联度水凝胶80 h基本降解,高交联度水凝胶不易降解.初步研究了CMCS水凝胶包埋牛血清白蛋白(BSA)的释放行为.     

羧甲基纤维素基复合水凝胶的研究及应用进展

羧甲基纤维素(CMC)水凝胶是一种具有亲水性的天然三维聚合物材料,具有高吸水性,因此以羧甲基纤维素钠制备的水凝胶安全无毒可生物降解,被广泛应用于医药、食品、农业和环境等领域,作为保鲜材料、抗菌材料、生物传感器、药物输送系统和去除重金属的吸附剂。本文按CMC复合水凝胶材料来源的不同,分类综述了大分子/CMC水凝胶、单体/CMC水凝胶和无机物/CMC水凝胶的研究进展、功能特性以及应用领域,为羧甲基纤维素复合水凝胶的研究提供一定的思路和理论依据。总结此方向研究中不同材料对羧甲基纤维素复合水凝胶性能的提升情况,同时对羧甲基纤维素水凝胶的应用前景进行了展望。     

MMA-BA-AA共聚反应中单粒径产物影响的研究

选择羧甲基纤维素(CMC)作为稳定剂,过硫酸铵为引发剂,采用种子乳液聚合的方法将甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、丙烯酸(AA)进行共聚合成了MMA-BA-AA共聚乳液。研究了羧甲基纤维素用量、引发剂用量、功能单体用量、单体用量和MMA/BA配比对乳液的影响。结果显示,羧甲基纤维素效果显著,既是稳定剂又是接枝底物,CMC用量为0.4%～0.5%,引发剂用量为0.2%～0.35%,丙烯酸AA用量为1%～2%,单体总量应低于45%,MMA/BA配比为1/1～9/7时,制备的乳液较好,且粒径分布呈单峰状态。     

基于MOF (Cu)@biochar气凝胶的制备及其在缓释氮肥上的应用

以羧甲基纤维素(CMC)、明胶和MOF(Cu)@biochar为原料,采用简单有效的冷冻干燥方法制备了(CMC/Gelatin/MOF(Cu)@biochar)杂化气凝胶,并用傅里叶变换红外光谱(FT-IR)、热重分析(TG)、X射线粉末衍射(XRD)、扫描电镜(SEM)和X射线光电子能谱(XPS)技术对其进行了表征;研究了MOF(Cu)@biochar含量、pH和不同的盐水溶液对杂化气凝胶溶胀行为的影响;以该气凝胶负载氯化铵,制备了一种新型缓释肥料(SRF),并研究了含2%(wt)SRF的沙性土壤的保水能力;SRF在土壤中第30天的累积释放率为79.4%;肥料在土壤中释放符合非Fickian扩散和阳离子交换的协同作用机理。     

羧甲基纤维素-壳聚糖水凝胶球的制备及性能

采用物理交联法制备了羧甲基纤维素(CMC)-壳聚糖(CS)共混水凝胶球;研究了共混球的耐酸碱性、溶胀性及对亚甲基蓝的吸附性能.结果表明,水凝胶球在弱酸和弱碱中具有一定的稳定性;随着羧甲基纤维素与壳聚糖质量比的增大,水凝胶的吸水溶胀率增加.在CMC与CS质量比为1∶4时制备的水凝胶呈规则球状.     

环糊精-壳聚糖/羧甲基纤维素水凝胶的制备及其缓释性能研究

首先通过壳聚糖(CS)、柠檬酸(CA)和环糊精(β-CD)制备了环糊精接枝壳聚糖载体(CS-CA-β-CD);然后将CS-CA-β-CD与羧甲基纤维素(CMC)共混制备了环糊精-壳聚糖/羧甲基纤维素水凝胶(CS-CA-β-CD/CMC),利用红外光谱(FTIR)、Zeta电位和透射电镜(TEM)对其结构进行表征;最后将其负载扑热息痛(Pa)进行释放性能研究,研究结果表明:这种药物载体对扑热息痛的载药量为76%、包封率为38%;对比环糊精接枝壳聚糖载体负载扑热息痛(CS-CA-β-CD/Pa),CS-CA-β-CD/CMC负载扑热息痛后的药物(CS-CA-β-CD/CMC/Pa)具有更好的缓慢释放性能。因此,CS-CA-β-CD/CMC/Pa药物在风湿性关节炎疼痛缓解治疗中具有一定的应用前景。     

水溶性两性纤维素衍生物──Ⅰ.羧甲基纤维素的季铵化

以羧甲基纤维素(CMC)为原料、3-氯-2-羟两基三甲基氯化铵(CHPAC)为季铵化剂,合成了一系列水溶性两性纤维素衍生物.研究了CMC季镇化反应的主要影响因素,发现不同的原料羧甲基取代度、反应用碱量、CHPAC用量及反应介质组成对CMC季铵取代度和CMC季铵化反应效率均有不同的影响,同时对原料CMC及其产物的IR、X光衍射和DSC谱图与溶液粘性行为进行了研究.     

NREL法测定木质纤维素原料组分的含量

对美国国家可再生能源实验室(NREL)方法定量木质纤维素原料中纤维素、半纤维素及木质素的实验条件进行了研究。72%浓硫酸水解1h、4%稀硫酸水解45min可将玉米秸秆中的纤维素、半纤维素降解为可用HPLC定量的单糖,适宜的样品添加量为0.5g。同时,将NREL法与国标法进行了比对,两种方法的测定结果基本一致。NREL法测定玉米秸秆中纤维素、半纤维素及木质素的含量分别为33.90%、23.89%和15.84%。     

纤维素基智能凝胶的制备、结构及性能研究

纤维素是自然界中最丰富的生物质资源,因其具有可再生性、生物相容性、无毒、可降解等诸多特性,纤维素及其衍生物不仅广泛应用于传统的工业领域,而且在药物控释、组织工程、可穿戴设备材料等领域也有着广阔的应用前景。受到工程技术应用需求的驱动,以纤维素及其衍生物为基材的智能凝胶材料已成为目前的研究热点。作者系统研究了纤维素基智能凝胶材料的制备、结构及性能。主要内容如下： 1.制备了纤维素基气凝胶并对其进行疏水改性,研究了疏水改性后的纤维素气凝胶材料在水下吸附气体的能力,并设计了纤维素基智能捕集器,用于连续不断地吸附从海底释放的甲烷气体。 2.制备了TEMPO氧化的纳米纤维素纤维,并将其用于增强聚丙烯酰胺/明胶形状记忆水凝胶的力学性能;制备的复合水凝胶展示了较好的形状记忆行为,并且该水凝胶的形状记忆性能具有较好的可重复性。 3.利用羧甲基纤维素制备了对多种金属阳离子响应的形状记忆水凝胶;能够通过改变羧甲基纤维素与金属离子之间的交联密度,调节该水凝胶的力学性能。 4.将羧甲基纤维素钠与聚丙烯酸（PAA）复合制备出具有较优异机械性能和自修复性能的聚丙烯酸/羧甲基纤维素钠水凝胶。通过简单的浸泡法,将该复合水凝胶浸泡在氯化钠（NaCl）溶液中,可以促进CMC和PAA之间的链缠结,进一步提升其机械性能。此外,由于水凝胶的导离子性,制备的水凝胶具有良好的传导性能,有望实现在电子皮肤或可穿戴设备中的应用。     

羧甲基壳聚糖/海藻酸钠半互穿网络水凝胶的制备及性能研究

以羧甲基壳聚糖(CMC)和海藻酸钠(SA)为原料,京尼平(GP)为交联剂,制备具有pH敏感性的CMC/SA半互穿网络(semi-IPN)水凝胶.利用特性黏数、红外光谱对CMC/SA水凝胶的半互穿网络结构及形成机理进行了分析与表征;对水凝胶的力学性能进行了测试;探讨了pH值及交联剂含量对水凝胶溶胀性能的影响.结果表明,京尼平交联的CMC/SA水凝胶具有半互穿网络结构.当w(CMC)∶w(SA)=5∶5时,CMC/SA水凝胶的断裂强度达到最大值(59 MPa),分别比纯的CMC(40 MPa)和SA(36 MPa)提高了47.5%和63.9%;当SA含量为60%时,CMC/SA水凝胶的断裂伸长率达到最大值(13.0%).当pH3.0时,溶胀率随pH值的增大而减小,pH=3.0时,溶胀率最小(186%);当pH3.0时,溶胀率随pH值的增大而增大,pH=9.0时,溶胀率最大(886%).京尼平交联的CMC/SA半互穿网络水凝胶具有明显的pH敏感性、溶胀可逆性及对pH的快速响应性.     

Radiation preparation and swelling behavior of sodium carboxymethyl cellulose hydrogels

Sodium carboxymethyl cellulose (CMC) is a kind of degraded polymer under γ-irradiation. However, in this work, it has been found that CMC crosslinks partially to form hydrogel by radiation technique at more than 20% CMC aqueous solution. The gel fraction increases with the dose. The crosslinking reaction of CMC is promoted in the presence of N₂ or N₂O due to the increase of free radicals on CMC backbone, but gel fraction of CMC hydrogel is not high (<40%). Some important values related to this kind of new CMC hydrogel synthesized under different conditions, such as radiation yield of crosslinking G(x), gelation dose R_g, number average molecular weight of network M_c were calculated according to the Charlesby–Pinner equation. The results indicated that although crosslinked CMC hydrogel could be prepared by radiation method, the rate of radiation degradation of CMC was faster than that of radiation crosslinking due to the character of CMC itself. Swelling dynamics of CMC hydrogel and its swelling behavior at different conditions, such as acidic, basic, inorganic salt as well as temperature were also investigated. Strong acidity, strong basicity, small amount of inorganic salts and lower temperature can reduce swelling ratio.     

辐射交联制备改性CMC水凝胶的溶胀行为研究

利用丙烯酰胺 (AAm)接枝改性纤维素 ,然后进行羧甲基化反应得到高取代度的丙烯酰胺 羧甲基纤维素钠 (AAm CMC Na) .对该材料进行γ射线辐照制备出新型改性CMC水凝胶 .研究了这种水凝胶的溶胀动力学、交联动力学以及温度、pH值和无机盐浓度对水凝胶溶胀行为的影响 ,并与CMC Na水凝胶进行了比较 .结果表明 ,该水凝胶和CMC Na水凝胶相比 ,优点在于辐照交联所用的剂量下降 ,而且所需的CMC浓度减少 .AAm CMC Na水凝胶的溶胀度随温度升高而增大 ,在pH为 6～ 8范围内达到最大值 ,并随无机盐浓度与吸收剂量增加而下降 ,表现出较好的温度敏感性和pH敏感性 ,可望作为吸水材料和水保持剂     

粉煤灰复合聚丙烯酸钠凝胶的制备及其溶胀性能

粉煤灰(CFA)存在的情况下,采用自由基溶液聚合法,以过硫酸钾(KPS)为引发剂,N,N'-亚甲基双丙烯酰胺(NNMBA)为交联剂,制备了粉煤灰复合聚丙烯酸钠凝胶(CFAPAANa)。 以丙烯酸单体质量为基准,当交联剂用量为0.08%,引发剂用量为0.4%,粉煤灰用量为3%,丙烯酸中和度为70%,聚合温度为70 ℃时,所合成的粉煤灰复合聚丙烯酸钠凝胶在蒸馏水和生理盐水中平衡溶胀比最高,分别为1556(g/g)和168(g/g)。 考察了复合凝胶在不同介质溶液中的溶胀动力学,保水性能以及在土壤中的降解行为。 溶胀动力学研究表明,蒸馏水中溶胀初期复合凝胶聚合物链段的扩散运动能够调控凝胶溶胀的快慢及程度,而生理盐水中水分子的平移和对流运动在凝胶的溶胀过程中起着关键性作用。 保水和降解实验结果表明,25 ℃时,50 h凝胶保水率为64%,土壤中50 d时降解率达60%。 相比于聚丙烯酸钠凝胶,粉煤灰复合凝胶保水率提高了8%。     

Synthesis of Carboxymethyl Cellulose Based Drug Carrier Hydrogel Using Ionizing Radiation for Possible Use as Site Specific Delivery System

A unique natural polymer based colon specific drug carrier was prepared from carboxymethyl cellulose (CMC) and acrylic acid (AAc) in aqueous solution employing γ‐radiation induced copolymerization and crosslinking. The effect of preparation conditions such as the natural polymer content and irradiation dose on gelation process was investigated. The swelling behavior of the prepared hydrogels was characterized by investigating the time and pH dependent swelling of the (CMC/AAc) hydrogels of different CMC content. The effects of the hydrogel composition and pH of the swelling medium on the swelling indices were estimated. The results show that the increment in the CMC content in the feed solution enhances the gelation process. The results also show the dependence of the swelling indices on both hydrogel composition and pH value of the swelling medium. To evaluate the ability of the prepared hydrogel to be used as a colon‐specific drug carrier, the release profile of theophylline was studied as a function of time at pH 1 and pH 7.     

Superabsorbent hydrogels based on cellulose for smart swelling and controllable delivery

Novel superabsorbent hydrogels were prepared successfully from carboxymethylcellulose sodium (CMC) and cellulose in the NaOH/urea aqueous system by using epichlorohydrin (ECH) as cross-linker. The structure and morphology of the hydrogels were characterized by FT-IR spectroscope, thermogravimetric analysis and scanning electron microscope. The results revealed that the CMC contributed to the enhanced size of pore, whereas cellulose as a strong backbone in the hydrogel to support it for keeping its appearance. Their equilibrium swelling ratio in distilled water and different physiological fluids were evaluated, indicating the maximum swelling ratio in water reached an exciting level of 1000 as the hydrogels still keeping a steady appearance. Moreover, the hydrogels exhibited smart swelling and shrinking in NaCl or CaCl₂ aqueous solution, as well as the release behavior of bovine serum albumin (BSA) that could be controlled by changing CMC content. The cellulose-based hydrogels are promising for the applications in the biomaterials area.     

Topochemical Engineering of Cellulose—Carboxymethyl Cellulose Beads: A Low-Field NMR Relaxometry Study

The demand for more ecological, highly engineered hydrogel beads is driven by a multitude of applications such as enzyme immobilization, tissue engineering and superabsorbent materials. Despite great interest in hydrogel fabrication and utilization, the interaction of hydrogels with water is not fully understood. In this work, NMR relaxometry experiments were performed to study bead–water interactions, by probing the changes in bead morphology and surface energy resulting from the incorporation of carboxymethyl cellulose (CMC) into a cellulose matrix. The results show that CMC improves the swelling capacity of the beads, from 1.99 to 17.49, for pure cellulose beads and beads prepared with 30% CMC, respectively. Changes in water mobility and interaction energy were evaluated by NMR relaxometry. Our findings indicate a 2-fold effect arising from the CMC incorporation: bead/water interactions were enhanced by the addition of CMC, with minor additions having a greater effect on the surface energy parameter. At the same time, bead swelling was recorded, leading to a reduction in surface-bound water, enhancing water mobility inside the hydrogels. These findings suggest that topochemical engineering by adjusting the carboxymethyl cellulose content allows the tuning of water mobility and porosity in hybrid beads and potentially opens up new areas of application for this biomaterial.     

Influence of cellulose nanowhiskers on the hydrolytic degradation behavior of poly(d,l-lactide)

This paper reports the preparation of bionanocomposites based on poly(d,l-lactide) and cellulose nanowhiskers (PDLLA/CNWs) and studies the influence of the CNWs on the hydrolytic degradation behavior of the polylactide. The hydrolytic degradation process was studied in a phosphate buffer medium through the sample weight loss and also by FTIR, DSC and TGA measurements. The presence of CNWs induced a strong delay in the hydrolytic degradation of the PDLLA, even when the concentration of the nanofillers was only 1%. This effect was related to the physical barrier created by the highly crystalline CNWs that inhibited water absorption and hence retarded the hydrolytic degradation of the bionanocomposites. In addition, the incorporation of cellulose nanocrystals in the PDLLA also made the biopolymer more thermally stable, increasing the initial temperature of mass loss even after the degradation in phosphate medium. The results presented here show the possibility of controlling the biodegradability and prolonging the service life of a polylactide through the incorporation of a small quantity of nanofillers obtained from renewable materials.     

Application of Polyvinyl Alcohol (PVA)/Carboxymethyl Cellulose (CMC) Hydrogel Produced by Conventional Crosslinking or by Freezing and Thawing

Hydrogels for this study were prepared from a mixture of PVA and CMC using three different techniques, i.e., freezing and thawing, electron‐beam irradiation or combined freezing and thawing and electron beam irradiation. A comparative study between the three techniques was carried out in terms of gel fraction (%) and swelling (%). It was found that the physical properties of the hydrogel were improved when the combination of freezing and thawing and irradiation were used rather than just freezing and thawing, or irradiation only. The effects of temperature and soil fertilizers on swelling (%) were examined to evaluate the usefulness of the hydrogel as a super absorbent in the soil. It was found that the swelling ratio increased as the composition of CMC increased in the blend. Hence, the blend having the composition 80/20 (CMC/PVA) was used as a super absorbent in the soil for agriculture. Moreover, the water retention increased in the soil containing this hydrogel. Thus, this type of hydrogel can be used to increase water retention in desert regions.     

Tuning the release rate of acidic degradation products through macromolecular design of caprolactone-based copolymers

Macromolecular engineering is presented as a tool to control the degradation rate and release rate of acidic degradation products from biomedical polyester ethers. Three different caprolactone/1,5-dioxepan-2-one (CL/DXO) copolymers were synthesized: DXO/CL/DXO triblock, CL/DXO multiblock, and random cross-linked CL/DXO copolymer. The relation of CL and DXO units in all three copolymers was 60/40 mol %. The polymer discs were immersed in phosphate buffer solution at pH 7.4 and 37 degrees C for up to 364 days. After different time periods degradation products were extracted from the buffer solution and analyzed. In addition mass loss, water absorption, molecular weight changes, and changes in thermal properties were determined. The results show that the release rate of acidic degradation products, a possible cause of acidic microclimates and inflammatory responses, is controllable through macromolecular design, i.e., different distribution of the weak linkages in the copolymers.