Pub Date : 2000-01-01DOI: 10.1002/(SICI)1099-0488(20000101)38:1<95::AID-POLB12>3.3.CO;2-X
B. Bauer, A. Ramzi, Da-Wei Liu, R. Scherrenberg, P. Froehling, J. Joosten
{"title":"Blends of fatty-acid-modified dendrimers with polyolefins This article is a US Government work and, as such, is in the public domain in the United States of America.","authors":"B. Bauer, A. Ramzi, Da-Wei Liu, R. Scherrenberg, P. Froehling, J. Joosten","doi":"10.1002/(SICI)1099-0488(20000101)38:1<95::AID-POLB12>3.3.CO;2-X","DOIUrl":"https://doi.org/10.1002/(SICI)1099-0488(20000101)38:1<95::AID-POLB12>3.3.CO;2-X","url":null,"abstract":"","PeriodicalId":16853,"journal":{"name":"Journal of Polymer Science. Part B, Polymer Physics","volume":"125 1","pages":"95"},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76909397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-12-15DOI: 10.1002/(SICI)1099-0488(19991215)37:24<3512::AID-POLB12>3.0.CO;2-#
N. Pogodina, H. Winter, S. Srinivas
Early stages of crystallization of polymers may be viewed as thermoreversible physical gelation in which molecular connectivity is introduced by crystallization. Effects of shear strain on the early stages of crystallization of a commercial isotactic polypropylene are studied by dynamic mechanical experiments. Shear creep with large strains (up to γ = 300) on the undercooled melt for short times (the time did not exceed 100 s) was followed by small amplitude oscillatory shear (SAOS) at a strain amplitude (γ a = 0.01) for gel-point detection. The imposed shear strongly accelerates gelation; gel times decrease in a power law with increasing strain. Strain applied during the crystal growth stage enhances gelation much stronger than strain applied in the earlier nucleation stage. For rapid gelation, frequency sweeps are not possible and new methods for gel-point detection need to be explored; here, we propose to estimate the gel point from the storage modulus growth at a single frequency. A value of 10% of the total growth of G' was found to be a good estimate for the gel point. High strain experiments show the complexity of underlying mechanisms of strain-enhanced crystallization and reveal at least two sequential stages in the structure development under shear: at the first stage, crystalline regions connect molecules into a loose network; at the second, stage-intense crystallinity growth within the network proceeds. Results have industrial importance in predicting/tuning structure development and connectivity growth during nonisothermal processing. Morphological study of the early stages of crystallization under strain is underway to explore molecular mechanisms, which govern the gelation process.
聚合物结晶的早期阶段可以看作是热可逆的物理凝胶，其中分子的连通性是由结晶引入的。通过动态力学实验研究了剪切应变对商品等规聚丙烯结晶早期阶段的影响。过冷熔体在短时间内(时间不超过100 s)发生大应变(γ = 300)的剪切蠕变，然后发生应变幅度(γ a = 0.01)的小振幅振荡剪切(SAOS)。施加的剪切强烈地加速了凝胶的形成;凝胶时间随应变的增加呈幂律递减。在晶体生长阶段施加的应变比在早期成核阶段施加的应变对凝胶化的促进作用强得多。对于快速凝胶，频率扫描是不可能的，需要探索新的凝胶点检测方法;在这里，我们建议从单频下的存储模量增长来估计凝胶点。发现G′总生长的10%的值是对凝胶点的一个很好的估计。高应变实验显示了应变增强结晶机制的复杂性，并揭示了剪切作用下结构发展的至少两个顺序阶段:第一阶段，晶体区域将分子连接成松散的网络;在第二阶段，在网络中进行强烈的结晶性生长。研究结果对于预测和调整非等温加工过程中的结构发展和连通性增长具有重要的工业意义。在应变下结晶早期阶段的形态学研究正在进行中，以探索控制凝胶过程的分子机制。
{"title":"Strain effects on physical gelation of crystallizing isotactic polypropylene","authors":"N. Pogodina, H. Winter, S. Srinivas","doi":"10.1002/(SICI)1099-0488(19991215)37:24<3512::AID-POLB12>3.0.CO;2-#","DOIUrl":"https://doi.org/10.1002/(SICI)1099-0488(19991215)37:24<3512::AID-POLB12>3.0.CO;2-#","url":null,"abstract":"Early stages of crystallization of polymers may be viewed as thermoreversible physical gelation in which molecular connectivity is introduced by crystallization. Effects of shear strain on the early stages of crystallization of a commercial isotactic polypropylene are studied by dynamic mechanical experiments. Shear creep with large strains (up to γ = 300) on the undercooled melt for short times (the time did not exceed 100 s) was followed by small amplitude oscillatory shear (SAOS) at a strain amplitude (γ a = 0.01) for gel-point detection. The imposed shear strongly accelerates gelation; gel times decrease in a power law with increasing strain. Strain applied during the crystal growth stage enhances gelation much stronger than strain applied in the earlier nucleation stage. For rapid gelation, frequency sweeps are not possible and new methods for gel-point detection need to be explored; here, we propose to estimate the gel point from the storage modulus growth at a single frequency. A value of 10% of the total growth of G' was found to be a good estimate for the gel point. High strain experiments show the complexity of underlying mechanisms of strain-enhanced crystallization and reveal at least two sequential stages in the structure development under shear: at the first stage, crystalline regions connect molecules into a loose network; at the second, stage-intense crystallinity growth within the network proceeds. Results have industrial importance in predicting/tuning structure development and connectivity growth during nonisothermal processing. Morphological study of the early stages of crystallization under strain is underway to explore molecular mechanisms, which govern the gelation process.","PeriodicalId":16853,"journal":{"name":"Journal of Polymer Science. Part B, Polymer Physics","volume":"24 1","pages":"3512-3519"},"PeriodicalIF":0.0,"publicationDate":"1999-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75576206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-02-15DOI: 10.1002/(SICI)1099-0488(19990215)37:4<275::AID-POLB2>3.0.CO;2-#
C. A. Harrison, J. S. Tan
Differential size-exclusion chromatography (SEC) is used to characterize complexes formed between gelatin and two synthetic polyelectrolytes, sodium poly(styrenesulfonate) and sodium poly(2-acrylamido-2-methylpropanesulfonate). The analysis is performed under aqueous, low-salt conditions where maximum complexation between gelatin and the polyelectrolytes occurs. The adsorption effects that are commonly encountered in conventional SEC for gelatin and other charged polymers chromatographed under these solution conditions are minimized, because the columns are constantly equilibrated with the analytes in the mobile phase. Analyte solutions of identical composition, but of higher or lower concentration than that contained in the mobile phase, are injected, resulting in positive or negative detector responses, respectively. This method can separate the complexes from individual components, and can be used to determine relative sizes and stoichiometries of the complexes as a function of both the input ratio of gelatin to polyelectrolyte and the molecular weight of the polyelectrolyte.
{"title":"Differential size‐exclusion chromatography for the analysis of gelatin–polyelectrolyte complexes","authors":"C. A. Harrison, J. S. Tan","doi":"10.1002/(SICI)1099-0488(19990215)37:4<275::AID-POLB2>3.0.CO;2-#","DOIUrl":"https://doi.org/10.1002/(SICI)1099-0488(19990215)37:4<275::AID-POLB2>3.0.CO;2-#","url":null,"abstract":"Differential size-exclusion chromatography (SEC) is used to characterize complexes formed between gelatin and two synthetic polyelectrolytes, sodium poly(styrenesulfonate) and sodium poly(2-acrylamido-2-methylpropanesulfonate). The analysis is performed under aqueous, low-salt conditions where maximum complexation between gelatin and the polyelectrolytes occurs. The adsorption effects that are commonly encountered in conventional SEC for gelatin and other charged polymers chromatographed under these solution conditions are minimized, because the columns are constantly equilibrated with the analytes in the mobile phase. Analyte solutions of identical composition, but of higher or lower concentration than that contained in the mobile phase, are injected, resulting in positive or negative detector responses, respectively. This method can separate the complexes from individual components, and can be used to determine relative sizes and stoichiometries of the complexes as a function of both the input ratio of gelatin to polyelectrolyte and the molecular weight of the polyelectrolyte.","PeriodicalId":16853,"journal":{"name":"Journal of Polymer Science. Part B, Polymer Physics","volume":"5 1","pages":"275-280"},"PeriodicalIF":0.0,"publicationDate":"1999-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90856316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1998-09-15DOI: 10.1002/(SICI)1099-0488(19980915)36:12<2237::AID-POLB20>3.0.CO;2-#
H. Okuzaki, T. Kuwabara, T. Kunugi
Polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the films obtained has been investigated. It was found that the thickness of the film and ambient relative humidity (RH) were crucial to the motion of film: An increase of the film thickness decreased the displacement of the bending but increased the bending stress. On the other hand, an increase of the ambient RH decreased both functions. The motion of film was caused by the difference of expansion on both sides of the film owing to anisotropic sorption of water vapor, which could be expressed by the diffusion-limited bending model. The diffusion coefficients calculated from the bending and recovery motion at 25°C, RH 50% were 12.2 × 10 -8 cm 2 s -1 and 3.5 × 10 -8 cm 2 s -1 , respectively. The maximum expansion of the film surface calculated from the bending curve was about 0.36%.
采用电化学方法合成了含高氯酸盐的聚吡咯薄膜，并对其弯曲和恢复运动进行了研究。研究发现，薄膜的厚度和环境相对湿度对薄膜的运动至关重要:薄膜厚度的增加使弯曲位移减小，但使弯曲应力增大。另一方面，环境相对湿度的增加降低了这两种功能。膜的运动是由于膜两侧对水蒸气的各向异性吸附造成的膨胀差异引起的，可以用扩散限制弯曲模型来表示。在25℃，相对湿度50%条件下，由弯曲运动和恢复运动计算得到的扩散系数分别为12.2 × 10 -8 cm 2 s -1和3.5 × 10 -8 cm 2 s -1。由弯曲曲线计算得到的膜面最大膨胀率约为0.36%。
{"title":"Theoretical study of sorption‐induced bending of polypyrrole films","authors":"H. Okuzaki, T. Kuwabara, T. Kunugi","doi":"10.1002/(SICI)1099-0488(19980915)36:12<2237::AID-POLB20>3.0.CO;2-#","DOIUrl":"https://doi.org/10.1002/(SICI)1099-0488(19980915)36:12<2237::AID-POLB20>3.0.CO;2-#","url":null,"abstract":"Polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the films obtained has been investigated. It was found that the thickness of the film and ambient relative humidity (RH) were crucial to the motion of film: An increase of the film thickness decreased the displacement of the bending but increased the bending stress. On the other hand, an increase of the ambient RH decreased both functions. The motion of film was caused by the difference of expansion on both sides of the film owing to anisotropic sorption of water vapor, which could be expressed by the diffusion-limited bending model. The diffusion coefficients calculated from the bending and recovery motion at 25°C, RH 50% were 12.2 × 10 -8 cm 2 s -1 and 3.5 × 10 -8 cm 2 s -1 , respectively. The maximum expansion of the film surface calculated from the bending curve was about 0.36%.","PeriodicalId":16853,"journal":{"name":"Journal of Polymer Science. Part B, Polymer Physics","volume":"26 1","pages":"2237-2246"},"PeriodicalIF":0.0,"publicationDate":"1998-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89109506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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