A polydopamine-polyurethane (PDA-WPU)-based polymeric matrix with efficient light-to-heat conversion properties that can initiate light-activated temperature elevations is presented. The polymerization of dopamine monomer in a pre-synthesized aqueous polyurethane dispersion resulted in hybrid polyurethane-polydopamine particles via the coating of discrete waterborne polyurethane (WPU) particles with photothermal polydopamine. The resulting polydopamine-polyurethane (PDA-WPU) dispersions presented a unimodal particle-size distribution and particle sizes that increased as a function of the initial dopamine concentration and polymerization time. Films cast from PDA-WPU dispersions were black-colored and presented a homogeneous morphology with contact angles that decreased with increasing PDA content. While the thermal decomposition behavior and thermal conductivity values of hybrid PDA-WPU films were improved relative to neat WPU films, the glass transition temperatures remained unaffected and the films presented acceptable mechanical properties. PDA-WPU films prepared with the highest amount of polydopamine reached 105.8 °C when irradiated with solar light at 3 sun for 20 min. Five min of irradiation with NIR laser light at 800 mW/cm2 elevated the temperatures of the PDA-WPU films from room temperature to 138.6 °C. Moreover, PDA-WPU dispersions were molded in the form of a container to investigate their potential in solar-driven water-evaporation applications. The hybrid PDA-WPU polymer matrix prepared via a facile postsynthesis modification of WPU dispersions with polydopamine synergistically possesses the features of both components and presents strong photothermal activity along with its easy-to-apply, nanoparticle-free, and environmentally friendly nature; thus, this matrix can be viewed as a promising candidate for a wide range of photo-driven applications.

No abstract

Form-stable phase change films composed of a polydopamine-polyurethane polymer matrix with photothermal conversion properties and polyethylene glycol (PEG) are presented. Surfaces of environmentally friendly waterborne polyurethane (WPU) particles in aqueous dispersions were coated with polydopamine to create a stable waterborne dispersion of a polydopamine-polyurethane (PDA-WPU) matrix, which intrinsically presents significant photothermal conversion properties, and PEG was directly integrated into the PDA-WPU matrix by simple mixing in the dispersion form. Successful film formation was achieved at PDA-WPU to PEG ratios of 1:1 and higher by weight, resulting in form-stable, homogeneous PDA-WPU/PEG phase change films. Incorporation of PEG into the amorphous PDA-WPU matrix was demonstrated to impart a semicrystalline character to PDA-WPU films, which also increased their thermal stability and thermal conductivity. Young's modulus of PDA-WPU/PEG films increased while the tensile strength and elongation at break values decreased as a function of PEG content, yet all films showed a flexible behavior. For the films prepared with the highest amount of PEG (PDA-WPU:PEG 1:1), the melting and solidifying enthalpies were calculated to be 81.1 and 77.9 J/g, respectively, and enthalpies remained the same over 60 consecutive heating−cooling cycles. The temperature of the PDA-WPU:PEG 1:1 film reached 74.8 °C under 20 min of solar irradiation at 150 mW/cm 2 with a solar-to-thermal energy conversion efficiency of 72.9%. In a cold environment, PDA-WPU/PEG films and their surroundings were shown to heat up more than controls under solar light and stay warmer after the solar irradiation was stopped. The temperature of the environment surrounded with the PDA-WPU/PEG film increased 10 °C more than the temperature of the control environment under 30 min of sunlight irradiation. Upon switching the sunlight irradiation off, the PDA-WPU/PEG environment cooled down to ambient temperature 10 min later than the control environment, demonstrating that these form-stable, flexible, and durable films can efficiently harvest and store sunlight and have strong potential as solar-driven thermoregulating materials.

No abstract

Hybrid waterborne polyurethane/polydopamine (WPU/PDA) matrix, showing the adhesive properties of PDA in its entirety, was utilized for the immobilization of lysostaphin (Lys), an important anti-staphylococcal agent, to obtain highly effective antibacterial and antibiofilm surface coatings. WPU/PDA matrix prepared by the encapsulation of WPU particles with PDA in aqueous dispersion was applied as coatings on substrates, and the facile incubation of the WPU/PDA-coated surfaces with Lys in aqueous solution resulted in WPU/PDA/Lys coatings that contained immobilized Lys on the surface. WPU/PDA/Lys coatings showed strong anti-Staphylococcus aureus activity with a 4 log reduction in the number of cells. Furthermore, WPU/PDA/Lys coatings were demonstrated to be durable without any enzyme leakage, and their antibacterial activity was preserved for at least 30 days and over multiple exposures to bacteria. WPU/PDA/Lys coatings presented significant antibiofilm activity against S. aureus with a 3.5 log reduction in the number of surface-attached bacteria. WPU/PDA/Lys coatings that are easy-to-apply to almost any surface, non-toxic, and environmentally friendly provide promising antibacterial and antibiofilm surfaces that are effective against S. aureus.