The role of entanglements for polymer crystallization

J.-U. Sommer

Leibniz-Insitut für Polymerforschung Dresden, Institut für Theorie der Polymere, Hohe Straße 6, 01069 Dresden
TU Dresden, Institut für Theoretische Physik, Zellescher Weg 17, 01069 Dresden

We use a coarse-grained polymer model to study the crystallization and melting behavior of long polymer chains in the dense state under various conditions. Our primary goal was to investigate the impact of the entanglement length on the properties of the lamellar crystal, in particular on the thickness selection, using algorithms to calculate the primitive path of the chains. In situ analysis of the local entanglement length prior to crystallization and the stem length and crystallinity at the same location reveals a direct correlation between the entanglement length and crystallization properties in the nucleation-controlled regime [1]. We have investigated various scenarios to change the apparent entanglement length in the system such as rapid cooling and cold-crystallization protocols, dilution of the melt by short chains, and the influence of solid substrates [2-4]. All studies confirm the correlation between entanglement length and thickness selection in the dense state. First results on non-concatenated ring polymer melts display a strong increase of the lamellar thickness and the degree of crystallization as compared to otherwise identical linear counterparts subject to the same thermal history [5].

[1] C.-F. Luo and J.-U. Sommer; Physical Review Letters 112, 195701 (2014). (link)
[2] C.-F. Luo, M. Kröger and J.-U. Sommer; Polymer 109, 71 (2017). (link)
[3] C.-F. Luo, M. Kröger and J.-U. Sommer; Macromolecules 49, 9017 (2016). (link)
[4] C.-F. Luo and J.-U. Sommer; ACS Macro Letters 5, 30 (2016). (link)
[5] H.-Y. Xiao, C.-F. Luo, D. Yan and J.-U. Sommer, manuscript (2017).

Interplay between the Relaxation of the Glass of Random L/D Lactide Copolymers and Homogeneous Crystal Nucleation: Evidence for Segregation of Chain Defects

C. Schick1,2 and R. Androsch3

1Institute of Physics and Competece Center CALOR, University of Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock, Germany
2Kazan Federal University, 18 Kremlyovskaya street, Kazan 420008, Russian Federation
3Center of Engineering Sciences, Martin Luther University Halle-Wittenberg, 06099 Halle/Saale, Germany

Random L isomer rich copolymers of poly(lactic acid) containing up to 4% D isomer co units have been cooled from the molten state to obtain glasses free of crystals and homogeneous crystal nuclei. The kinetics of enthalpy relaxation and the formation of homogeneous crystal nuclei have then been analyzed using fast scanning chip calorimetry [1]. It has been found that the relaxation of the glass toward the structure/enthalpy of the supercooled liquid state is independent of the presence of D isomer co units in the chain. Formation of homogeneous crystal nuclei in the glassy state requires the completion of the relaxation of the glass [1,2]. However, nucleation is increasingly delayed in the random copolymers with increasing D isomer chain defect concentration. The data show that the slower formation of homogeneous crystal nuclei in random L/D lactide copolymers, compared to the homopolymer, is not caused by different chain segment mobility in the glassy state but by the segregation of chain defects in this early stage of the crystallization process [3].

[1] E. Zhuravlev, et al., Polymer 52, 1983 (2011). (link)
[2] R. Androsch, et al., Europ. Polym. J. 53, 100 (2014). (link)
[3] R. Androsch, and C. Schick, J. Phys. Chem. B 120, 4522 (2016) (link)

Nucleation processes in protein aggregation

Tuomas P. J. Knowles

University of Cambridge, Department of Chemistry, UK

Filamentous protein aggregation underlies a number of functional and pathological processes in nature. This talk focuses on the formation of amyloid fibrils, a class of beta-sheet rich protein filament. Such structures were initially discovered in the context of disease states where their uncontrolled formation impedes normal cellular function, but are now known to also possess numerous beneficial roles in organisms ranging from bacteria to humans. The formation of these structures commonly occurs through supra-molecular polymerisation following an initial primary nucleation step. In recent years it has become apparent that in addition to primary nucleation, secondary nucleation events which are catalysed in the presence of existing aggregates can play a significant role in the dynamics of such systems. This talk describes our efforts to understand the nature of the nucleation processes in protein aggregation as well as the dynamics of such systems and how these features connect to the biological roles that these structures can have in both health and disease.

Highly oriented and crystalline semi-conducting and conducting polymer films prepared by high-temperature rubbing

Martin Brinkmann (1), Amer Hamidi-Sakr (1), Laure Biniek (1), Patrick Lévêque (2), Jean-Louis Bantignies (3),  David Maurin (3), Nicolas Leclerc (4)

(1) Université de Strasbourg, CNRS, ICS UPR22, F67000 Strasbourg, France
(2) Université de Strasbourg, CNRS, ENGEES, INSA, ICube UMR 7357, F-67000 Strasbourg, France
(3) Université de Montpellier, Laboratoire Charles Coulomb, F34095 Montpellier, France
(4) Université de Strasbourg, CNRS, ICPEES, UMR 7515, F67000 Strasbourg, France

This contribution focuses on recent advances in growth control and oriented crystallization of semi-conducting and conducting polymers. Particular emphasis will be given to the progress made in high-temperature rubbing of such polymers. This effective large scale alignment method can orient a large palette of polymer semiconductors (PSCs) with n- or p-type character without the use of an alignment substrate. The concurrent roles of the polymer molecular weight distribution and the rubbing temperature (TR) on the in-plane orientation have been rationalized for P3HT and PBTTT. Continue reading Highly oriented and crystalline semi-conducting and conducting polymer films prepared by high-temperature rubbing

Rheology of self-nucleated poly(ε-caprolactone) melts

D. Cavallo1, F. Barbieri1, L. Sangroniz2, A. Santamaria2, R.G. Alamo3 and A.J. Müller2

1Department of Chemistry and Industrial Chemistry, Genova (Italy)
2POLYMAT/Polymer Science and Technology Dept., San Sebastián, (Spain)
3Department of Chemical and Biomedical Engineering, Tallahassee, (USA)

Contrary to low molar mass molecules, semicrystalline polymers exhibit a strong influence of the melt-annealing conditions on the re-crystallization. An enhanced concentration of nuclei is found after a mild melting treatment, in comparison to annealing at high temperatures and long times. [1,2] The intimate nature of these “self-nuclei” is still under debate, since they are elusive to the most commonly adopted characterization techniques. [2,3]

In this work, the self-nucleation process is studied by probing the effect of self- nuclei on the rheological properties of the non-equilibrium melt. Three poly(ε- caprolactone)s with different molar mass were investigated by shear rheometry. The viscoelastic functions of the melt were determined at the same temperatures, reached either from the solid state or from the melt, i.e., with or without the presence of self-nuclei.
Continue reading Rheology of self-nucleated poly(ε-caprolactone) melts

Chain Folding of Semicrystalline Polymers

Toshikazu Miyoshi

Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA

There is a long-standing controversy about chain-folding structure and mechanism of long polymer chains during crystallization. This information is a key factor to understand the crystallization mechanisms at the molecular levels. Recently, solid-state (SS) NMR combined with selectively 13C isotopic labelling has been successfully utilized to determine local chain trajectory of folded polymer chains in single and bulk crystals.1-6 In this talk, we will discuss various physical effects on chain folding and crystallization mechanisms of several polymers such as Poly(L-Lactic, Acid),1, 2 Isotactic-poly(1-butene),1, 3, 4 and Isotactic-Polypropylene.1, 5, 6 Continue reading Chain Folding of Semicrystalline Polymers

Model Experiments for the Crystallization of Conjugated Polymers

G. Reiter1, F.M. Keheze1, D. Raithel2, R. Hildner2, D.Schiefer3, M. Sommer3

1Physikalisches Institut, Universität Freiburg, Freiburg, Germany
2Experimentalphysik IV, University of Bayreuth, Bayreuth, Germany.
3Institut für Makromolekulare Chemie, Universität Freiburg, Freiburg, Germany

Much insight into crystallization of long chain polymers can be gained by studying mono-lamellar single crystals. Because of the kinetically determined lamellar thickness and the corresponding variations in melting temperature, polymer crystals allow for self-seeding, i.e., crystals can be re-grown from a melt, which contains a few thermodynamically stable remnants of pre-existing crystals acting as seeds. Employing such a self-seeding approach, we demonstrated that large single crystals can be grown even from long poly(3-hexylthiophene) (P3HT) chains, with a control over the number density, size, and internal structure of these crystals exhibiting monoclinic form II with interdigitated hexyl side groups [1]. Continue reading Model Experiments for the Crystallization of Conjugated Polymers

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