Thermoplastic elastomers (TPEs) combine high elasticity with melt processability due to their structural features being based on physical associations rather than chemical crosslinking. Their mechanical properties are governed by the interplay of the different dynamics present in the system (i.e., hard block associations and soft block mobility) combined with their morphology. Irrespective of their exact chemical structure or type of association (crystals, hydrogen bonds, or glassy domains), many soft TPEs show a reduction in toughness at elevated temperatures. In this study, we investigate the high‐temperature mechanical properties of a model series of industrially relevant TPEs via systematically varying composition and molecular weight. The results show an increase in temperature resistance and in large‐strain stress response as chain length increases. We underline the key parameters that influence the mechanical behavior and explain the observed effect of molecular weight on both the temperature‐ and rate‐dependent large‐strain response. A physical network‐based model is presented that can explain the experimental findings assuming an improved network connectivity and extended lifetime of the entangled segments with increasing molecular weight.

An intestine‐on‐chip has been developed to study intestinal physiology and pathophysiology as well as intestinal transport absorption and toxicity studies in a controlled and human similar environment. Here, we report that dynamic culture of an intestine‐on‐chip enhances extracellular matrix (ECM) remodeling of the stroma, basement membrane production and speeds up epithelial differentiation. We developed a three‐dimensional human intestinal stromal equivalent composed of human intestinal subepithelial myofibroblasts embedded in their own ECM. Then, we cultured human colon carcinoma‐derived cells in both static and dynamic conditions in the opportunely designed microfluidic system until the formation of a well‐oriented epithelium. This low cost and handy microfluidic device allows to qualitatively and quantitatively detect epithelial polarization and mucus production as well as monitor barrier function and ECM remodeling after nutraceutical treatment.

The mechanical properties of multiblock copolymer thermoplastic elastomers (TPEs) are governed by the interplay of different reversible dynamics [e.g., hard block (HB) association and chain entanglements]. Understanding how these physical processes influence the high-temperature deformation behavior is relevant as many TPEs lose toughness with increasing temperature. Increasing molecular weight (Mw) improves their temperature resistance that is attributed to an increase in network connectivity. Indeed, longer chains are characterized by more HBs per chain and by a longer lifetime of the entanglements in the amorphous phase. Both the associating HB and disentanglement dynamics are temperature and rate dependent. To further understand the interconnected role of Mw, temperature and rate dependencies on the mechanical properties, we perform Temperature Scanning Stress Relaxation (TSSR) tests. The method consists of measuring the stress relaxation of the materials as the temperature monotonically increases, allowing us to probe the stress response as the HBs progressively disassociate due to the increase in temperature. The results show that increasing Mw improves the high-temperature relaxation behavior, allowing the material to retain more stress than its low Mw counterpart as the temperature increases. This distinction does not show itself when performing standard small strain dynamic mechanical thermal analyses. Depending on the deformation experienced before the TSSR is performed, different relaxation behaviors are observed illustrating the importance of the current microstructure in determining the mechanical properties. The TSSR approach is well-suited to benchmark the high-temperature stress-bearing properties of network-based polymers whose morphology and, hence, properties are strongly deformation dependent.

We discuss the connection between high-temperature mechanics, block structure, and composition of a model series of industrially relevant, soft, thermoplastic elastomers (TPEs) containing polydisperse hard blocks (HBs). The high-strain deformation behavior of these materials results from the combination of multiple dynamics in the system, i.e., the HB associations and the mobile and entangled amorphous phase. Many soft-TPEs show a reduction in toughness with increasing temperature. Molecular weight (Mw) has been shown to improve the temperature-dependent mechanics by increasing network connectivity. In this work, we investigate the possibility to increase the network connectivity by tuning block length at constant Mw and composition. The average number of HBs per chain can be used to quantify network connectivity; however, by using block statistics, we show how increasing this value is not enough to increase the high-temperature mechanics, especially in the case of polydisperse HBs. Since temperature affects the HB ability to associate with each other, only the number of associated HBs per chain determines network connectivity. The experimental results are consistent with modeling predictions, revealing how decreasing the average block length influences the crystal stability, which ultimately controls network connectivity, and how this relationship is affected by temperature.

Failure of industrially relevant soft-TPEs at different temperatures, rates, and molecular weights, and linked to morphological and molecular structure changes.