Polydopamine Particles Reinforced Poly(vinyl alcohol) Hydrogel with NIR Light Triggered Shape Memory and Self‐Healing Capability

Abstract

following freezing/thawing under strain, which induces the second cross-linking due to crystallization of PVA chains. The reversible formation and melting of PVA crystallites enables the temporary shape fixation and recovery. Chen et al. also constructed a shape memory hydrogel based on stronger and weaker H-bonding by introducing tannic acid (TA) into the PVA hydrogel networks. The stronger multiple H-bonding between PVA chains and TA acts as the permanent cross-links and the weaker H-bonding among PVA chains works as the temporary cross-links. [20] However, the shape memory and selfhealing PVA hydrogel still encounters some challenges. The first is how to control the SM&SH process spatially and temporally by appropriate stimulus. Most SM&SH hydrogels were thermally activated, but one disadvantage is that the direct heating will lead to temperature rising of the entire material. [21,22] Other stimulating means such as air, water, and pH can also trigger the shape recovery, but those stimuli are limited in practical applications. [23][24][25][26] In contrast, the remote stimulations such as ultrasound and light are very easy to achieve local focus and quantitative stimulation. [27,28] Previously we firstly proposed the use of therapeutic ultrasound to trigger the shape memory of a PVA hydrogel containing a small amount of melamine. [19] In this study, we will try to use near-infrared (NIR) to trigger the SM&SH process by employing the photothermal effect of polydopamine. As a safe and noncontact stimulus, NIR light is widely used in the field of biomedicine. Huang et al. proposed a one-pot method to produce a double network containing both permanent and temporary cross-linking structures through chemically cross-linked polyacrylamide (PAM) and physically cross-linked gelatin. Graphene oxide (GO) was introduced into the hydrogel matrix to serve as energy convertor to convert NIR irradiation to thermal energy. [29] Although GO has been widely used as nearinfrared light energy convertor, the dispersion problem and the interaction with the matrix are the bottlenecks that limit its application. [30,31] The second challenge is the contradiction between mechanical strength and self-healing performance. In most cases, the hydrogel with self-healing function has a lower mechanical strength, which in practice means no useful in many circumstances. There are some approaches to improve the mechanical properties of hydrogels, such as introducing physical and chemical cross-linkers or reinforced fillers. [32][33][34] HydrogelsThis study focuses on developing a facile approach to prepare biocompatible poly(vinyl alcohol) (PVA) composite hydrogels containing polydopamine particles (PDAPs) with ultrafast near-infrared (NIR) light-triggered shape memory and self-healing capability. The PVA-PDAPs composite hydrogels with excellent mechanical properties can be achieved after freezing/thawing treatment, and the formation of physically cross-linked networks from the hydrogen bonding (H-bonding) between PVA and PDAPs. Due to the exce...

A novel photothermo-responsive nanocarrier for the controlled release of low-volatile fragrances

“…Polydopamine was synthesized following a previously reported method. 32 To a Tris buffer solution (pH ¼ 8.5, 100 mL) was added 0.5 g dopamine hydrochloride, and the resulting mixture was stirred for 12 h in an atmosphere of air at room temperature. Aer the reaction completion, PDA suspensions were collected by centrifugation (8000 rpm), washed three times with water and dried in a vacuum for 24 h.…”

“…1, the employed protocol involves the synthesis of mesoporous silica nanoparticles (MSNs) by a general method 34 followed by immersion in an ethanol solution of Sandalore (SA) and surface modication via the in situ self-polymerization of dopamine in a weakly alkaline medium. 32,37 The resulting nanocomposites were denoted as SA x /MSN@PDA y to indicate their composition when necessary, where x is equal to the fragrance loading content (LC) dened above and y represents the mass percent of PDA layer relative to silica. The amount of PDA deposited on the particle surface could be easily regulated by changing the monomer feed ratio in the polymerization stage.…”

“…Herein, the fragrance oil was rst loaded into the silica cage and further blocked by the PDA lm in situ formed on the particle surface. The PDA possesses plentiful polar groups such as catechol, amine, and imine moieties, available for hydrogen bonding interactions with entrapped molecules, 32,33 which would lead to increased diffusion barrier of the payload. More importantly, the surface coating will act as a switch to modulate the aroma volatilization via responding to light stimulus.…”

Nanofiber‐Based Hydrogels: Controllable Synthesis and Multifunctional Applications

“…In recent years, the requirement and development speed of soft intelligent materials are increasing with each passing day. Among these smart materials, flexible actuators triggered by various external stimulus such as electrical stimulation, light magnetic field, temperature, pH value, and humidity, have attracted a lot of attention due to their promising applications in many fields . Although some progresses have been obtained in the past few years, the preparation of flexible actuator with controllable moving direction and rapid shape recovery property is still a great difficulty .…”

Carbon nanotubes array reinforced shape‐memory epoxy with fast responses to low‐power microwaves

“…Shape memory polymers (SMPs) can be fixed into a temporary shape by external constraint and recovered to initial shapes when exposed to outer stimulus . By molecular structures, SMPs can be divided into many categories: epoxy‐based, styrene‐based, polyurethane (PU)‐based, acrylate‐based, poly(vinyl alcohol) (PVA)‐based, and so on. And some new SMPs, such as polypeptide, chitosan, and poly(vinyl acetate), were also discovered recently.…”