Overcoming the Tradeoff Between Processability and Mechanical Performance of Elastomeric Vitrimers

Abstract

Vitrimers are polymer networks with dynamic covalent bonds that allow the network to reconfigure its connectivity while maintaining a constant number of chemical bonds at all temperatures. The melt viscosity of vitrimers thus gradually decreases with temperature. This behavior makes vitrimers more difficult to process than typical thermoplastics using conventional processing techniques, such as extrusion. Although many strategies have been reported to address this issue, it remains challenging to overcome a key tradeoff between improving the processability or the mechanical performance. Herein, this work presents a new strategy for overcoming this tradeoff in the context of elastomeric vitrimers. The approach entails the cross‐linking of a functionalized low‐glass transition (Tg) polymer matrix with an incompatible high‐Tg polymer featuring pendant groups with complementary reactivity. When compared to a conventional homogeneous vitrimer, the microphase‐separated materials prepared by reactive extrusion present improved tensile properties and creep resistance at room temperature while also exhibiting enhanced processability at high temperature. These enhanced properties are a consequence of the combination of the phase separation between the soft and hard phases, the restriction of dynamic cross‐linking reactions within the interfacial zones, and the judicious selection of the Tg of the hard phase to be in between the use and processing temperatures.

Improving the Thermomechanical Properties and Processability of Elastomeric Vitrimers Using Thermoreversible Organic Nanofillers

“…19−21 For example, the room temperature creep resistance of a boronic ester-based vitrimer with a styrene−butadiene rubber matrix is improved by introducing metal−ligand coordination 22 and hydrogen bonding 23 our team recently reported a new approach that is based on controlling the morphology of an elastomeric vitrimer in a modular fashion. 24 We found that microphase-separated materials prepared by reactive processing exhibit comprehensively improved mechanical properties and processability compared to those of analogues that are nanophase-separated or homogeneous. This desirable behavior is attributed to a combination of factors: the size of the high-T g domains, restriction of the cross-linking reactions within the interfacial zones, and the judicious choice of the T g of the hard phase to be above the use temperature but below the processing temperature.…”

“…Combining ionic and noncovalent interactions with dynamic covalent bonds have also been explored. − For example, the room temperature creep resistance of a boronic ester-based vitrimer with a styrene–butadiene rubber matrix is improved by introducing metal–ligand coordination and hydrogen bonding to the network structure. In this context, our team recently reported a new approach that is based on controlling the morphology of an elastomeric vitrimer in a modular fashion . We found that microphase-separated materials prepared by reactive processing exhibit comprehensively improved mechanical properties and processability compared to those of analogues that are nanophase-separated or homogeneous.…”

Sustainable Benzoxazine-Sulfur Copolymer with Dynamic Linkages: Recycling, Reprocessing, Self-Healing, and Shape Recovery (R2S2)

“…Even though recycling or repurposing polymers appeared as an appealing strategy, repetitive processing imbues deterioration in properties due to uncontrollable structural alterations and heterogeneities developed upon reuse. Recently, tailoring of dynamic covalent bonds with triggered reversibility at the molecular level has shown great promise to overcome these challenges. − The pioneering work in 2010–2011 by Kloxin et al and Liebler et al discussed the introduction of dissociative and associative covalent adaptable networks (CANs) in thermosets; the latter are classified as “vitrimers” and have significantly progressed over the years. − This led to an advancement in polymer chemistry using the fundamentals of simple exchange reactions, allowing features of thermoplastics within thermosets. , …”

Vitrimer Nanocomposites for Highly Thermal Conducting Materials with Sustainability

“…Hence, vitrimer systems exhibit the capacity for reversible reactions, allowing for the breaking and formation of bonds in response to external stimuli while maintaining the overall count of chemical bonds. This distinctive characteristic arises from the investigation and study of various dynamic covalent bonds, encompassing ester [13,14], carbonate [15], carbamate [16][17][18], acetal [19,20], imine [21][22][23], boron ester [24][25][26], diboroxine [27], silyl ether [28,29], disulfide [30,31], triazolium [32], and others [33], within this system.…”