Crystallization Behavior of Polymer Langmuir Monolayers Observed by High-Resolution Atomic Force Microscopy

Kenta Iwashima, Kenji Watanabe, and Jiro Kumaki

Department of Organic Materials Science, Yamagata University, Japan

Polymer monolayers spread on a water surface transform from an isolated chain to amorphous, then to a crystalline state upon compression, which can be transferred at each stage onto a substrate for observation by atomic force microcopy (AFM) [1]. Previously, we successfully observed a folded chain crystal (FCC) of an isotactic poly(methyl methacrylate) (it-PMMA) [2], its melting behavior in situ at high temperature [3], and crystallization of single isolated chains [4] at a molecular level by AFM. Continue reading Crystallization Behavior of Polymer Langmuir Monolayers Observed by High-Resolution Atomic Force Microscopy

Kinetics of crystallization in a model poly(thiophene)

Alberto Salleo

Materials Science and Engineering Department
Stanford University, Stanford CA 94305

Semicrystalline conjugated polymers have attracted much interest as disruptive materials for flexible, low-cost and printed electronics. Indeed, these polymers can be used as semiconductors in thin-film transistors, light-emitting diodes, solar cells and sensors. Furthermore, they have recently been made in stretchable forms. From the materials perspective, it has been known for decades that their electronic performance, as measured by carrier mobility, is very strongly dependent on the film microstructure. One of the goals of this field is to learn how to manipulate the microstructure through processing. In spite of this recognized fundamental need, very little is known about the crystallization processes in these polymers, which are crucial in microstructure formation. We used a model poly(thiophene), poly(3-hexyl-ethyl-thiophene)-(P3EHT)- to perform an in-depth, multi-technique study of crystallization kinetics and its effect on charge transport. Continue reading Kinetics of crystallization in a model poly(thiophene)

Polymorphs Selection in Random Copolymers

Y.F. Men, Y.T. Wang, and J.Y. Zhao

State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Renmin Street 5625, 130022 Changchun, P.R. China

Many polymers exhibit different polymorphous structure depending on crystallization condition. In random copolymers, the melt state is often structured having segregations of crystallizable chain segments originating from the melting of previous crystals when the system has not been treated at temperature high enough (much higher than the equilibrium melting temperature of the corresponding crystals). Clearly, when being annealed at different melt temperatures, the size of such segregations can be varied so that the followed crystallization can be affected under different confinements. We report in this work a peculiar observation of polymorph selection during crystallization of a butane-1/ethylene random copolymer of 10 mol% ethylene co-units. Continue reading Polymorphs Selection in Random Copolymers

Full characterization of multi-phase, multi-morphological kinetics in flow-induced crystallization of isotactic Polypropylene at elevated pressure

Gerrit W.M. Peters, Enrico Troisi, Giovanna Grosso

Eindhoven University of Technology, Department of Mechanical Engineering, Polymer Technology Group, PO Box 513, 5600 MB Eindhoven, The Netherlands

Understanding the complex crystallization behavior of isotactic polypropylene (iPP) in conditions comparable to, e.g. injection molding, where the polymer melt experiences a combination of high shear rates and elevated pressures, is key for modeling and, therefore, predicting the final structure and properties of iPP products. Coupling a unique experimental setup, capable to apply wall shear rates similar to the ones experienced during processing and carefully control the pressure before and after flow is imposed, with in-situ X-ray scattering and diffraction techniques (SAXS and WAXD) at fast acquisition rates (up to 30 Hz), a well-defined series of short-term flow experiments are carried on using 16 different combinations of wall shear rates (110 to 440 1/s) and pressures (100-400 bar) [1]. A complete overview on the kinetics of structure development during and after flow is presented. Continue reading Full characterization of multi-phase, multi-morphological kinetics in flow-induced crystallization of isotactic Polypropylene at elevated pressure

Effect of Solvent Affinity on Crystallization-driven Fibril Growth Kinetics in Diblock Copolymer Solutions

Junfan Chen and Wenbing Hu

State Key Lab of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China

Crystallization-driven fibril growth of one block under nano-confinement of another non-crystalline block in diblock copolymer solutions has raised the interests in two important fields. One is the self-assembly of nano-particles for hierarchical construction [1, 2]. Another is the neuro-fibrillary tangles in Alzheimer’s disease [3]. The selective affinity of solvent in two blocks may influence the kinetics of the fibril growth, on processing the nano-particle assembly or hindering the disease development. We have recently performed dynamic Monte Carlo simulations of diblock copolymers in athermal solutions, with fibril crystallization of one block induced by a crystalline template but under the confinement of another amorphous block [4]. Continue reading Effect of Solvent Affinity on Crystallization-driven Fibril Growth Kinetics in Diblock Copolymer Solutions

Thermal Behavior of Silk Protein

P. Cebe1, D. Thomas1, J. Merfeld1, B. P. Parlow2, D. L. Kaplan2, R. Alamo3, A. Wurm4, E. Zhuravlev4, and C. Schick4

1Physics and Astronomy Dept., Tufts University, Medford, MA 02155 USA
2Biomedical Engineering Dept., Tufts University, Medford, MA 02155 USA
3Chemical and Biomedical Engineering Dept., Florida State University-FAMU, Tallahassee, FL 32310 USA
4 Institute for Physics and Competence Center Calorimetry of Interdisciplinary Faculty, University of Rostock, Rostock, Germany

Silk is a naturally occurring biopolymer which has been used in textiles for over 5000 years. Silk stands as an exemplar of the class of fibrous proteins. The properties of silk protein are related to its semicrystalline nature, imparted by the secondary structures, such as the non-crystalline helices and random coils, and the crystalline beta pleated sheets. Using techniques of condensed matter polymer physics, we investigate the structure and thermal behavior of silk fibroin [1-3]. Continue reading Thermal Behavior of Silk Protein

Oriented Recrystallization of Carbon-Coated Pre-oriented Ultrathin Polymer Films

Shouke Yan, and Le Ma

State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China

The recrystallization behavior of carbon-coated preoriented polymer thin films was studied by means of transmission electron microscopy combined with electron diffraction and spectroscopy. It was found that vacuum evaporated carbon layer can keep the molecular chain orientation of pre-oriented polymer thin films. This demonstrates the existence of strong fixing effect of vacuum evaporated carbon layers on the surface layer of the polymer films, which prevents the relaxation of surface extended macromolecular stems in the crystals or at least from a complete relaxing during high-temperature melting. Continue reading Oriented Recrystallization of Carbon-Coated Pre-oriented Ultrathin Polymer Films

Amyloids from the origin to the end of life

Roland Riek1, Marielle Wälti1, Cedric Eichmann, and Jason Greenwald1

1Vladimir Prelog Weg 2, ETH, ETH Hönggerberg, CH-8093 Zurich

Protein aggregation is observed in many diseases including Alzheimer’s disease. These protein aggregates are termed amyloids. Amyloids are composed of pairs of tightly interacting, many-stranded, repetitive, inter-molecular beta-sheets termed the cross-beta-sheet structure. Because of this structure, amyloids can grow by recruitment of the same protein while their repeat can transform a weak activity into a potent one through cooperativity and avidity. Continue reading Amyloids from the origin to the end of life

Avoidance of Density Anomalies as a Structural Principle for Semicrystalline Polymers

Klaus Schmidt-Rohr

Chemistry Department, Brandeis University, Waltham, Massachusetts, USA

For a detailed analysis of the crystallization process, a realistic view of the chain trajectories in the lamellar semicrystalline morphology is of interest. We have come to the conclusion that the textbook models of melt-crystallized semicrystalline polymers unintentionally but inevitably contain layers with a higher density than in the crystallites.[1] Such density anomalies can be avoided by chain ends at the crystal surface and/or chain tilt in the crystallites. NMR shows that most CH3 end groups of polyethylenes (PEs) are indeed in all-trans chains near the crystal surface. As a consequence, many chain folds cannot be tight, also in agreement with NMR data. Continue reading Avoidance of Density Anomalies as a Structural Principle for Semicrystalline Polymers

Isothermal Crystallization of Triple Crystalline Biodegradable PEO-b-PCL-b-PLLA Triblock Terpolymers

J. K. Palacios1, A. Tercjaks2, J. Zhao3, N. Hadjichristidis3, A. J. Müller*1,4

1POLYMAT and Polymer Science and Technology Department, Faculty of Chemistry, University of the Basque Country UPV/EHU, Donostia-San Sebastián, Spain
2Chemical and Environmental Engineering Department, Polytechnic School, University of the Basque Country UPV/EHU, Donostia-San Sebastián, Spain
3King Abdullah University of Science and Technology (KAUST), Physical Sciences and Engineering Division, KAUST Catalysis Center, Thuwal, Saudi Arabia
4IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

 PEO-b-PCL-b-PLLA triblock terpolymers are fascinating materials, as they can develop three different crystalline phases1. Adjusting the block composition and crystallization conditions, each block is able to crystallize sequentially and separately from a homogeneous melt. Thus, crystallization drives superstructure formation into mixed spherulites that include lamellae of PLLA, PCL and PEO. The PLLA block crystallizes first at higher temperatures upon cooling from the melt (and templates the morphology), then the PCL block, and finally the PEO block2. In this work, a three-stage crystallization protocol was applied to study the isothermal crystallization kinetics of each block. The crystallization was studied by WAXS, SAXS, DSC and AFM. At the PLLA crystallization temperatures, both PCL and PEO molten chains caused a strong diluent effect on PLLA crystallization. Continue reading Isothermal Crystallization of Triple Crystalline Biodegradable PEO-b-PCL-b-PLLA Triblock Terpolymers