Elsevier

Materials Letters

Volume 284, Part 2, 1 February 2021, 129007
Materials Letters

The effect of chitosan form on the shape memory properties of polyurethane based composites

https://doi.org/10.1016/j.matlet.2020.129007Get rights and content

Highlights

  • Novel chitosan/polycaprolactone-urethanes shape memory bio-composites were developed.

  • The form of chitosan affects the shape recovery temperature.

  • The time of shape recovery may be modulated by the form of chitosan incorporated within polymer matrix.

Abstract

The continuous progress in the medicine and biotechnology demands development of novel biomaterials with multiple functions. This multifunctionality may be accomplished through combining synthetic polymers with shape memory properties and natural polymers. Shape memory composites consisting of poly(caprolactone-urethane) and chitosan (PU-2/3 PCL CH) were synthesized and evaluated in terms of structure–function correlation. Chitosan was incorporated in a form of microspheres (CH-Mic) or as the macromolecule unit (CH-m) of PCL-based polyurethane matrix (PU-2/3 PCL). The effect of chitosan on shape memory properties and transition temperature was evaluated. The PU-2/3 PCL CH-m composite demonstrated a lower transition temperature (Ttrans) of the shape recovery in comparison to neat PU-2/3 PCL matrix and PU-2/3 PCL CH-Mic composites. The composites with CH-m exhibited shape recovery immediately after reaching Ttrans whereas neat polymers and composites consisting of CH-Mic required five minutes pre-heating time before initialization of the shape recovery process.

Introduction

Multifunctional biomaterials based on shape memory polymers (SMP) become promising class of materials for developing more advanced and user -friendly medical devices [1]. Shape-memory polymers (SMPs) are mechanically active or smart materials, which can be fabricated in a specific permanent shape, deformed and fixed in a second, temporary shape. The intrinsic mechanism for shape memory behavior in thermal responsive SMPs is the reversible freezing and activation of polymeric chain motion in the switching segments below and above the transition temperature (Ttrans), respectively. Polyurethane (PU) based on cross-linked poly(ε-caprolactone) (PCL) are one of the thermo-responsive SMP that exhibit reversible transition behavior associated with melting of PCL crystalline phase in a physiologically relevant range [2]. The previous study [3] revealed that chitosan incorporated into PU shape memory matrix may improve biocompatibility of the final material system due to its non-toxicity, antioxidant, antimicrobial, and antifungal bioactive properties. Despite the recent research on PU/chitosan composites [4], [5] the comprehensive data on structure - function correlation is required to design effective multifunctional material system. In this study the effect of the chitosan form i.e. microspheres or chitosan macromolecules on thermomechanical properties, microstructure and shape memory properties were evaluated.

Section snippets

Materials and methods

Two types of chitosan/polyurethane composites consisting of mixture of 3-branched and 2-branched PCL-based polyurethane matrix (PU-2/3 PCL) and chitosan microspheres (CH-Mic) or chitosan macromolecule units (CH-m) were developed. CH-Mic were prepared according to emulsification/chemical crosslinking method, using two types of crosslinkers – TPP solution 8% (v/v) and glutaraldehyde solution 35% (wt.%). Dimethyl sulfoxide - soluble chitosan was firstly prepared by the depolymerization of chitosan

Results and discussion

The functional properties i.e. shape memory capability, mechanical properties or transition temperature are strongly affected by chemical structure. The most significant features affecting shape memory and mechanical properties are hydrogen bonds. In case of PU macromolecules either intermolecular or intramolecular hydrogen bonds can be formed between urethane units. Moreover, chitosan active groups can also participate at hydrogen bond interaction. In order to analyze the chemical structure of

Conclusions

Development of multifunctional materials that exhibit independent material functions correlated with a particular component require in-depth structure/function analysis. In this study it was explored the crystallinity and shape memory properties of the composites consisting of PCL-based polyurethane matrix and chitosan incorporated in form of microspheres or macromolecule unit. Incorporation of chitosan in both forms led to small decrease shape recovery evaluated after first cycle.

CRediT authorship contribution statement

Monika Bil: Conceptualization, Investigation, Writing - original draft, Writing - review & editing, Project administration, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was financed by National Science Centre Poland on the basis of a decision number DEC-2012/07/D/ST8/02588.

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