Simple and Versatile Protocol for Preparing Self-Healing Poly(vinyl alcohol) Hydrogels

Abstract

As the role of polymers in undergraduate chemistry curricula continues to expand, opportunities will emerge for adopting experiments involving smart materials (i.e., materials that change properties in response to external stimuli). Slime demonstrations are routinely carried out with poly­(vinyl alcohol) (i.e., PVA) hydrogels because the polymer is inexpensive and nontoxic, and the resulting material has interesting physical properties. This report describes an activity where PVA is processed into an autonomous self-healing smart material. Specifically, students prepare rigid PVA hydrogels using a simple freeze/thaw protocol. The resulting material is cut, and the severed edges are pressed together to initiate autonomous self-healing. Healing is observed by measuring sufficiently high (i.e., >40 kPa) uniaxial tensile strengths at the repaired surface. Preparing the hydrogel does not require chemical additives beyond commercially available PVA (i.e., M w ∼ 145,000 g mol–1) and water. Additionally, the tensile strength can be determined using a spring force gauge and a ruler. The simplicity of the procedure, use of low-cost materials, and ties to green chemistry make the activity suitable for use in high school or introductory college chemistry settings. Furthermore, procedural variation and more rigorous analysis make the activity versatile by allowing the protocol to be used in second- or third-year chemistry courses (e.g., organic and physical chemistry). Overall, the activity provides a straightforward approach to introducing students to modern topics in polymer chemistry and materials science.

O Ensino Sobre Ciências Em Pressupostos Históricos E Filosóficos Para O Ensino De Química

“…O PVA é um polímero sintético obtido a partir da hidrólise do poli(acetato de vinila) porque o monômero do PVA não é estável (YOUNG, 2005). Ele é usado nas mais diversas aplicações, como espumas, esponjas, revestimentos, tintas, colas e lentes de contato (MORRIS et al, 2019).…”

Tough Hybrid Hydrogels Adapted to the Undergraduate Laboratory

“…Owing to the wide-ranging applicability, complex molecular makeup, and unusual mechanics of contemporary hydrogels, exposure to the topic in a hands-on, experimental setting is valuable for students in various disciplines including chemistry, physics, materials science, and biomedical sciences. − A basic understanding of hydrogels and visualization of their properties would serve students across multiple disciplines, and as such, we introduce with this work an adaptable protocol intended for the undergraduate laboratory . This is complementary to a recent laboratory experimental procedure related to self-healing hydrogels for high school students and undergraduates . Likewise, several explorations into the preparation of simple hydrogels have appeared in this Journal , targeting different students at various educational levels. − …”

“…20 This is complementary to a recent laboratory experimental procedure related to self-healing hydrogels for high school students and undergraduates. 21 Likewise, several explorations into the preparation of simple hydrogels have appeared in this Journal, targeting different students at various educational levels. 22−25 We were particularly intrigued by a seminal report describing simple protocols and formulations that led to gels with astonishing tensile and compressive properties.…”

Photo-Cross-Linked Hydrogel Replication of Small Objects: A Multistep Final Project for Undergraduate Polymer Laboratories

“…As methodologies that were once relegated to research laboratories due to their complexity have become optimized to the point of industrial adoption, more undergraduate chemistry laboratory experiences are being geared toward advanced synthetic strategies such as atom transfer radical polymerization (ATRP) and living polymerization. − Similarly, the optical properties and industrial flexibility of poly­(dimethylsiloxane) (PDMS)-based materials has inspired the development of teaching laboratories based on the synthesis and characterization of siloxane polymers. − Although bulk elastomers have been a primary product of the petroleum industry for decades, hydrogels may be better examples for chemistry course material as they encompass many of the classic essential concepts in polymer chemistry education: radical polymerization, cross-linking, bulk chemical and mechanical properties, macromolecular and network architecture, intuitive structure–property relationships, and applications in familiar and emerging fields. , For example, hydrogels are being reported as delivery vehicles for hydrophobic biomolecules and tissue repair scaffolds for myocardial infarction damage. , Their relative youth in comparison to some of the core chemistry disciplines also lends itself to engaging exploratory experiences that feel authentic at the educational laboratory level, such as a recent example of self-healing hydrogels that can be assembled with minimal complication using poly­(vinyl alcohol) (PVA) and water …”

“…15,16 Their relative youth in comparison to some of the core chemistry disciplines also lends itself to engaging exploratory experiences that feel authentic at the educational laboratory level, such as a recent example of selfhealing hydrogels that can be assembled with minimal complication using poly(vinyl alcohol) (PVA) and water. 17 In this respect, the development of new undergraduate level laboratory experiences incorporating aspects of polymeric hydrogels would be beneficial to the future of polymer research. Equally important, by relating the work done in the teaching laboratory setting to current research with a clear impact potential, 2 students may not only develop interest in the field of polymers but also gain confidence in their ability to make an impact in meaningful research efforts based on their success developing these relatively new systems on a small laboratory scale.…”