Structure–property relations in semi‐crystalline combinatorial poly(urethane‐isocyanurate)‐type hydrogels

Abstract

Within the fields of regenerative medicine and tissue engineering, the development of tough hydrogel biomaterials is a challenging topic that has received much attention over the past few years. Recently, a method was developed to synthesize tough combinatorial poly(urethane-isocyanurate) (PUI)-type hydrogels by the trimerization of mixtures of NCO-functionalized prepolymers. As this synthesis approach allows a large degree of freedom in terms of polymer network design with a high level of control over the polymer network structure, the resulting systems are ideally suited for studying structure-property relations in tough hydrogel systems. In this work, we aim to systematically investigate the influence of introducing a hydrophobic component into a PUI polymer network on the mechanical properties of the resulting PUI hydrogels. Additionally, the effect of (the degree of ) crystallinity of the hydrophobic network component is investigated. For this, two series of combinatorial PUI hydrogels are synthesized, based on a hydrophilic poly(ethylene glycol) prepolymer and increasing amounts of either a crystallizable hydrophobic prepolymer (poly(ε-caprolactone)) or an amorphous hydrophobic prepolymer (poly(propylene glycol)). It is shown that the toughness of amorphous PUI hydrogels is hardly influenced by the hydrophobic content, whereas the toughness of semi-crystalline PUI hydrogels strongly increases with increasing hydrophobic content. Also, the toughness of the latter hydrogels increases further with increasing degree of crystallinity of the hydrogel. Finally, it is shown that the semi-crystalline PUI hydrogels are promising materials for biomedical adhesive and coating applications, as well as for load-bearing biomedical applications within the fields of tissue engineering and regenerative medicine.

Polymer-Based Hydrogels Applied in Drug Delivery: An Overview

“…Crystallinity influences the physical and mechanical properties of hydrogels, including their strength, stiffness, and swelling behavior. In terms of crystallinity, hydrogels can be broadly categorized into two types, with amorphous polymer-based hydrogels [224,225] and semi-crystalline polymer-based hydrogels [17,23,226].…”

“…Semi-crystalline polymer-based hydrogels are hydrogels that exhibit a combination of amorphous and crystalline regions within their polymer network [11,23,226]. Unlike amorphous polymer-based hydrogels that lack long-range structural order, semi-crystalline polymer-based hydrogels contain regions where the polymer chains arrange themselves in an ordered, crystalline manner, interspersed with amorphous regions [11,17].…”

“…Unlike amorphous polymer-based hydrogels that lack long-range structural order, semi-crystalline polymer-based hydrogels contain regions where the polymer chains arrange themselves in an ordered, crystalline manner, interspersed with amorphous regions [11,17]. The presence of crystalline regions in semi-crystalline hydrogels introduces additional structural organization and can significantly influence the material properties [226]. The development of semi-crystalline polymer-based hydrogels involves careful control of the synthesis and processing conditions to promote the formation of crystalline regions [23].…”

“…The development of semi-crystalline polymer-based hydrogels involves careful control of the synthesis and processing conditions to promote the formation of crystalline regions [23]. Factors such as polymer selection, crystallization temperature, and annealing can influence the degree of crystallinity within the hydrogel [23,226]. The unique combination of crystalline and amorphous regions in semi-crystalline hydrogels offers advantages in various applications.…”

Poly(urethane-isocyanurate) networks: Synthesis, properties and applications

“…33 The syntheses and material properties of novel PUI networks are presented in Chapters 5, 6, 7 and 8 of this thesis. 48,[62][63][64] To illustrate the high resilience of materials crosslinked by isocyanurate rings, the glass transition temperatures of various dense polyisocyanurate networks are shown in Scheme 2.10 and compared to an analogous 2K PU network that does not contain isocyanurate rings.…”