Characterization of viscoelastic properties of polymeric materials through nanoindentation

2005 ◽  
Vol 45 (2) ◽  
pp. 130-136 ◽  
Author(s):  
G. M. Odegard ◽  
T. S. Gates ◽  
H. M. Herring
Keyword(s):  
Viscoelastic Properties ◽  
Polymeric Materials

scholarly journals Influence of Network Topology on the Viscoelastic Properties of Dynamically Crosslinked Hydrogels

2020 ◽  
Author(s):  
Emilia M. Grad ◽  
Isabell Tunn ◽  
Dion Voerman ◽  
Alberto S. de Léon ◽  
Roel Hammink ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Network Topology ◽  
Viscoelastic Properties ◽  
Polymeric Materials ◽  
Direct Result ◽  
Reference Network ◽  
Self Healing ◽  
Combine Stress ◽  
Synthetic Cell

Biological materials combine stress relaxation and self-healing with non-linear stress-strain responses. These characteristic features are a direct result of hierarchical self-assembly, which often results in fiber-like architectures. Even though structural knowledge is rapidly increasing, it has remained a challenge to establish relationships between microscopic and macroscopic structure and function. Here, we focus on understanding how network topology determines the viscoelastic properties, i.e. stress relaxation, of biomimetic hydrogels. We have dynamically crosslinked two different synthetic polymers with one and the same crosslink. The first polymer, a polyisocyanopeptide (PIC), self-assembles into semi-flexible, fiber-like bundles and thus displays stress-stiffening, similar to many biopolymer networks. The second polymer, 4-arm poly(ethylene glycol) (starPEG), serves as a reference network with well-characterized structural and viscoelastic properties. Using one and the same coiled coil crosslink allows us to decouple the effects of crosslink kinetics and network topology on the stress relaxation behavior of the resulting hydrogel networks. We show that the fiber-containing PIC network displays a relaxation time approximately two orders of magnitude slower than the starPEG network. This reveals that crosslink kinetics is not the only determinant for stress relaxation. Instead, we propose that the different network topologies determine the ability of elastically active network chains to relax stress. In the starPEG network, each elastically active chain contains exactly one crosslink. In the absence of entanglements, crosslink dissociation thus relaxes the entire chain. In contrast, each polymer is crosslinked to the fiber bundle in multiple positions in the PIC hydrogel. The dissociation of a single crosslink is thus not sufficient for chain relaxation. This suggests that tuning the number of crosslinks per elastically active chain in combination with crosslink kinetics is a powerful design principle for tuning stress relaxation in polymeric materials. The presence of a higher number of crosslinks per elastically active chain thus yields materials with a slow macroscopic relaxation time but fast dynamics at the microscopic level. Using this principle for the design of synthetic cell culture matrices will yield materials with excellent long-term stability combined with the ability to locally reorganize, thus facilitating cell motility, spreading and growth.

scholarly journals Recent Applications of Advanced Atomic Force Microscopy in Polymer Science: A Review

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1142 ◽  
Author(s):  
Phuong Nguyen-Tri ◽  
Payman Ghassemi ◽  
Pascal Carriere ◽  
Sonil Nanda ◽  
Aymen Amine Assadi ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Chemical Characterization ◽  
Super Resolution ◽  
Polymeric Materials ◽  
Polymer Materials ◽  
Polymer Science ◽  
Force Microscopy ◽  
Atomic Force ◽  
Nanoscale Characterization

Atomic force microscopy (AFM) has been extensively used for the nanoscale characterization of polymeric materials. The coupling of AFM with infrared spectroscope (AFM-IR) provides another advantage to the chemical analyses and thus helps to shed light upon the study of polymers. This paper reviews some recent progress in the application of AFM and AFM-IR in polymer science. We describe the principle of AFM-IR and the recent improvements to enhance its resolution. We also discuss the latest progress in the use of AFM-IR as a super-resolution correlated scanned-probe infrared spectroscopy for the chemical characterization of polymer materials dealing with polymer composites, polymer blends, multilayers, and biopolymers. To highlight the advantages of AFM-IR, we report several results in studying the crystallization of both miscible and immiscible blends as well as polymer aging. Finally, we demonstrate how this novel technique can be used to determine phase separation, spherulitic structure, and crystallization mechanisms at nanoscales, which has never been achieved before. The review also discusses future trends in the use of AFM-IR in polymer materials, especially in polymer thin film investigation.

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