Design of self-healing biodegradable polymers

Abstract

A biodegradable thermoplastic polymer has been formulated by solubilizing Murexide (M) salts in a commercial biodegradable vinyl alcohol copolymer (HVA). The Murexide has been employed as a self-healing filler with the aim to impart the auto-repair ability to the formulated material. Three different percentages (1, 3, and 5 mass%) of filler have been solubilized in HVA to evaluate the effect of the filler concentration on the thermal and self-healing properties of the resulting polymeric materials. The samples have been thermally characterized by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analyses (TGA), while their self-healing ability has been evaluated through the estimation of the storage modulus recovery, measured by Dynamic Mechanical Analysis (DMA). The results of DSC analysis have highlighted that the increase of the amount of Murexide anticipates the thermal events such as glass transition, crystallization and melting. TGA measurements have evidenced that, although there is a reduction of thermal stability of the materials in the presence of a high concentration of M, the polymer still remains stable up to 270 °C. Healing efficiency higher than 80%, at a temperature beyond 60 °C, has been detected for the samples loaded with 3 and 5 mass% of Murexide, thus confirming the efficacy of this compound as an auto-repair agent and the relationship between the self-healing efficiency and its amount. For a temperature lower than 70 °C, the healing tests, carried out at different values of tensile deformation frequency, have highlighted a frequency-dependent healing efficiency. This dependence becomes negligible at higher temperatures for which the healing efficiency approaches the value of 100%.

Self‐Healing Ability of Poly(PEGMA‐5‐UPy) Evaluated by Thermomechanical Analysis

“…In addition, the supramolecular interactions may hinder the crystallization process, making the polymer more amorphous and causing a consequent decrease of X c values. [ 61 ]…”

“…In addition, the supramolecular interactions may hinder the crystallization process, making the polymer more amorphous and causing a consequent decrease of X c values. [61] Figure 7 illustrates the profiles of the mass loss (see Figure 7a) and derivative mass loss (see Figure 7b) curves, for the characterized copolymers. All the analyzed materials show a thermal degradation profile characterized by two main stages of decomposition, the first between 300 °C and 400 °C and the second one 7a,b), determines an increase in the thermal stability of the Poly(PEGMA), conferring to the Poly(PEGMA-5-UPy) and Poly(PEGMA-7.8-UPy) copolymers values of T d5% (temperature corresponding to a mass loss of 5 wt%), illustrated in Table 2, higher than ≈30 °C, with respect to the Poly(PEGMA) and Poly(PEGMA-2.5-UPy) samples.…”

“…In this last case, the self-repair ability has been conferred to the material by adding a molecule capable of acting as a healing agent. [48,[57][58][59][60][61] In recent years, an important step forward in supramolecular chemistry has been possible thanks to the work of Beijer et al, with the synthesis of the ureidopyrimidinone (UPy) dimer, that, due to its high dimerization constant, is considered "the novel building-block for self-assembly." [62] Since then, UPy units, combined with several elastomeric matrices such as poly(butyl acrylate) (PBA) and poly(ethylene glycol) (PEG), have been employed to formulate self-healing copolymers, whose adhesion properties have been investigated to develop biocompatible materials, having potential application in tissue engineering or for obtaining flexible electronic devices.…”

“…In this last case, the self‐repair ability has been conferred to the material by adding a molecule capable of acting as a healing agent. [ 48,57–61 ]…”

Self-healing nanocomposites via N-doped GO promoted “click chemistry”

“…7). The healing efficiency was determined as the recovery of the storage modulus using the formula ( E SH / E V × 100), 33 where E V is the storage modulus of the virgin sample and E SH is the storage modulus of the healed sample. Three time tests were performed for each composition for obtaining similar results.…”