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1、附件 毕业论文(设计)外文资料翻译外文出处：附 件：1.外文资料翻译译文2.外文原文题目壳聚糖/聚乙烯醇复合水凝胶的制备与对苯酚吸附研究院 （系）化工与环境工程学院专业高分子材料与工程班级高分子05-1班学号05014010121姓名指导教师2009年 6月10日附件1：外文资料翻译译文壳聚糖-聚乙烯醇复合水凝胶溶胀度及其生物相容性2.2.1壳聚糖溶液和PVA溶液制备 首先，聚乙烯醇水凝胶的制备，是先称5.0g聚乙烯醇粉末使其在100ml纯净水中进一步完全溶解，同时在电磁搅拌下，温度控制752（溶液A），就像我们团队之前的报道所示。7-9。5的聚乙烯醇完全溶解后，让其冷却到室温和用1.0 M盐
2、酸（）把pH值控制在（2.000.05）。壳聚糖水凝胶（壳聚糖）制备采用相似的步骤，称2.5g壳聚糖在250ml 2的醋酸溶液（）中，电磁搅拌48小时（溶液B）。2.2.2壳聚糖和聚乙烯醇复合水凝胶制备用不同量的聚乙烯醇溶液（溶液A）加入到1.0的壳聚糖溶液（溶液B）获得以下几种壳聚糖/聚乙烯醇水凝胶，分别质量比为（0:1），（1:3 ），（1:1），（3:1）和（1:0）和用1.0M氢氧化钠溶液把pH值调节在（4.000.05）。将该混合物继续搅拌5分钟，直到聚乙烯醇和壳聚糖完全形成了清澈溶液。然后，缓慢加入交联剂（戊二醛），并不断搅拌。在溶液凝胶初期，戊二醛的最后浓度为1和5（质量分数）。
3、随着进一步反应，溶液不断塑化，接着在室温下其让干燥72至120 h，最后在40干燥24小时（恒重）。壳聚糖-聚乙烯醇复合水凝胶样品的化学交联反应产生凹痕已确定为（X： Y： Z）三种因素，X为壳聚糖的含量，Y为聚乙烯醇的含量，Z为戊二醛（质量分数%）。例如，样品组成确定为壳聚糖/聚乙烯醇/戊二醛=（1:3:1）,则：25的壳聚糖，75聚乙烯醇和1.0（质量分数）戊二醛。干凝胶储存在干燥器之前，要记录样品每一个特征。2.3.4.1 溶胀度测试流体吸收研究是初步分析生物降解材料至关重要的步骤。测定流体摄取量，所有壳聚糖-聚乙烯醇水凝胶的样品摩尔比为0:1，1:3，1:1，3:1和1:0时，制备如前
4、一节所描述的，都是质量比（W%），然后在37下，浸泡于吸附液体中。经过不同时间长度的浸泡后，用滤纸把表面上的水去掉，小心的将样品放到适当的容器中，然后测定样品的湿重（g），分析与浸泡时间的关系9。计算如下面的公式： 每个样品溶胀度实验重复做三次，取平均值。3.4.1 溶胀度测试 溶胀度的实验主要研究壳聚糖/聚乙烯醇水凝胶合成时，不同混合比例和戊二醛交联剂用量对溶胀度的影响。典型的溶胀行为如图4所示：壳聚糖/聚乙烯醇配比（25：75），交联剂用量为1%和5%。简单地说，从观察表明，最初30分钟出现迅速大规模吸收，其次变为缓和，超过192小时后，基本稳定不变。看上去样品体积有明显的膨胀。结果表明，
5、强交联度越大，膨胀体积也越大，膨胀最大达到壳聚糖-聚乙烯水凝胶交联之前体积的7倍，当交联剂用量分别为1.0和5.0时膨胀度下降到400和200。这现象是由于高分子链在反应时形成交错的网络空间结构，减少了分子活动性和水凝胶内一些不利于膨胀率的亲水基团。因此，这些结果相当于说明水凝胶溶胀的行为原因。在戊二醛加入反应之前，聚乙烯醇分子链结合到壳聚糖分子链段上，形成了水凝胶网络结构。接着，当戊二醛加入，发生化学交联反应，在链段间形成共价键，固定聚合物和降低流动性，引起较少的溶胀率，也许，只有一半不到的混合物发生交联反应。 改变壳聚糖在聚乙烯醇中的配比，分析影响如图5所示。实验表明，壳聚糖的含量对水凝胶
6、溶胀行为的影响尤为明显，固定交联剂在5.0时，水凝胶溶胀度随壳聚糖浓度的增加而减少，壳聚糖/聚乙烯醇= 50:50时，达到最低值。 这些结果能支持理解交联反应如何发生在复合水凝胶内，戊二醛与壳聚糖的胺基反应，比与聚乙烯醇的羟基反应多很多。最小值出现在50：50处（图5）可能是胺基与羟基数目相等有关，从而形成较硬的壳聚糖/聚乙烯醇链，令两者流动性迅速下降。尽管目前的研究不同于其他壳聚糖的研究报道，但聚乙烯醇和壳聚糖的溶胀行为与这些结论相似，聚乙烯醇的溶胀度在500%以上，壳聚糖大约是200%，取决于溶液中的PH值，温度等等。4 结论在目前的研究中，壳聚糖-聚乙烯醇混合物都是由人工用化学交联得到的
7、双功能醛。结果表明，通过改变壳聚糖与聚乙烯醇中的比例，不同的交联剂浓度，水凝胶的整体性能是可以改变的。这次的实验报告已指出溶胀性能与壳聚糖含量的增加，还有交联试剂用量的增大有很大的关系。这现象产生的原因是形成了一个十分紧密的网络结构。此外，细胞相容性实验已经证明，所有实验结果评价是无毒，无排斥性和生物相容性好。总之，这些研究扩大了壳聚糖/聚乙烯醇混合物等一些生物材料在医学领域的应用的潜力，如生物材料，毒品运载工具和皮肤组织工程。附件2：外文原文（复印件）Properties and biocompatibility of chitosan lms modied by blending with
8、 PVA and chemically crosslinked2.2.1 Chitosan and PVA solution preparationBriey, PVA hydrogels were prepared by fully dissolving 5.0g of polymer powder without further purication in 100 ml of Milli-Q water, under magnetic stirring, at temperature of 75 2 (solution A), as previously reported by our g
9、roup 79. PVA 5% solution was let to cool down to room temperature and the pH was corrected to (2.00 0.05) with 1.0 M HCl (Sigma). Chitosan hydrogels (Chi) were produced in a similar procedure by fully dissolving 2.5g in 250.0ml of Milli-Q water with 2% of CH3COOH (Sigma),under magnetic stirring for
10、48 h (solution B).2.2.2 Chitosan, PVA and blends lms preparationDifferent quantities of PVA (solution A) were added into the 1.0% chitosan solution (solution B) to obtain chitosan/PVA mass ratios of (0:1), (1:3), (1:1), (3:1), and (1:0) and pH was corrected to (4.00 0.05) with 1.0 M NaOH solution. T
11、he mixture was kept under stirring for 5 min until the PVA and chitosan completely formed a clear solution. Then, the crosslinker reagent (GA) was slowly added under constant stirring. The nal concentration of GA in the gel solution precursors was 1% and 5% (wt%). Further in thesequence, the solutio
12、n was poured into plastic moulds and let drying for 72120 h at room temperature, and nally dried at 40 for 24 h (constant weight). Chitosan/PVA samples chemically crosslinked were identied by (X:Y:Z) that is, X as chitosan content, Y as PVA content, and Z as GA (wt%). For instance, sample identied a
13、s Chi/PVA/GA (1:3:1) represents the following proportion of reagents: 25% chitosan, 75% PVA and crosslinked with 1.0% GA (wt%). The dried gel was stored in a desiccator before all sub-sequent characterization procedures.2.3.4.1 Swelling test Fluid absorption studies are of paramount importance for p
14、reliminary analysis of biode-gradable materials. For uid-uptake measurements, all the specimens of the chitosan/PVA hydrogels with molarratios of 0:1, 1:3, 1:1, 3:1, and 1:0 were prepared as described in the previous section, were weighed (W0) before being immersed in SBF at 37. After immersion for
15、different time periods, the samples were carefully removed from the medium and, after wiping off water excess on the surface with lter paper, they were weighed for the determination of the wet weight (Wf) as a function of the immersion time 9. SBF absorption (S) is given bythe eq. Each SBF absorptio
16、n experiment was repeated three times and the average value was taken to validate theresults.3.4.1 Swelling test Swelling experiments were conducted with Chi/PVA blends, with different polymer proportions and crosslinkedby GA. A typical swelling behavior is shown in Fig.4 performed for Chi/PVA blend
17、 25:75 before and after chemical crosslinking with 1% and 5% of content. Briey, the observed pattern indicated an initial rapid mass uptake,usually in approximately 30 min, followed by mass stabilization over a 192 h period. Visual inspection of the samples also shows appreciable volume increase. Th
18、e results have revealed a strong inuence of the crosslinkingon the swelling volume, from about 700% in Chi/PVA sample before crosslinking, it dropped to 400% and 200%,with 1.0% and 5% GA, respectively. That fact is attributed to a more rigid network formed by the inter-intra polymer chain reactions
19、that have occurred, reducing the exibility and number of hydrophilic groups of hydrogel which is unfavorable to the swelling rate. So, these results are cor-responding to the hydrogel mechanism. Before GA reaction, the PVA chains are physically entangled with the chitosan chains, forming a hydrogel
20、network. In the sequence, when the GA content was increased the chemical crosslinking has occurred, forming covalent bonds among chains, xing and reducing polymer mobility, which resulted in the lower swelling rate, in case, less than half of that blend without chemical crosslinking.。The effect of c
21、hitosan to PVA ratio was also analyzed and the results are presented in Fig. 5. It was veried that the swelling behavior is especially inuenced by the chitosan content in the blend, crosslinked at 5.0%GA,where the swollen mass reduced by increasing the chitosan concentration and reaching a minimum v
22、alue at Chi/PVA =50:50. The swelling degree reduced from 200%(pure PVA) to 100% (50:50 Chi/PVA), then raised to about140% at Chi/PVA ratios of 75:25 and 100% chitosan.These results are supported by understanding the cross-linking reaction which has occurred in the blended hydrogels, where the amine
23、groups of chitosan are more reactive to GA than hydroxyls of PVA. The minimum value observed at 50:50 (Fig.5) is probably related to the overall balance between amine and hydroxyl crosslinking which is caused by the formation of a rigid structure amongst the Chi/PVA chains, reducing drastically thei
24、r possibility of solution uptake. Despite of the present research being different from other reported chitosan studies, similar trends regarding to the swelling behavior of PVA and chitosan supported these ndings, where PVA has a swelling degree above 500% and chitosan of about200%, depending of cou
25、rse of the solution medium, pH,temperature and so forth.4 ConclusionIn the present research, chitosan/PVA blends were synthesized and chemically crosslinked with bi-functional aldehyde. The results have shown that by altering the proportion of chitosan to PVA, associated with different crosslinker c
26、oncentration, the overall properties from hydrogels can be modied. The systems investigated have indicated a signicant reduction on the swelling behavior as the chitosan content was increased and also as the amount of crosslinking reagent was raised. This fact was attributed to the formation of a mo
27、re rigid network. Moreover, cell biocompatibility assays have proven that all systems evaluated are non-toxic, biotolerant, and biocompatible. In summary, these developed blends based on chitosan/PVA have broadened the number of choices of biomaterials to be potentially used in biomedical applications such as biomaterial, drug delivery vehicles and skin tissue engineering.
