Photoactive Polymers

Introduction

Photoactive ploymers also known as photosensitizer, sensitizer and light crosslinking agent which are transfer light energy to some reactants that are not sensitive to visible light in order to improve and expand its photosensitivity. The photochemical reaction initiated by the photoactive ploymer is called photosensitivity reaction. Photoactive ploymers have applications in various fields ranging from solar cells and 3D printing to photodynamic therapy (PDT) due to their unique physicochemical properties.

The general properties of photoactive ploymers

• Photoactive ploymers can be activated by light.
• Photoactive ploymers can absorb a sufficient amount of photons and have a sufficient concentration in the system.
• Photoactive ploymers can transfer their energy to the reactants.

Application

The photoactive ploymers are extensively applied to functional materials, chemical engineering and medical chemistry. The main applications of photoactive ploymers are as follows.

• Highly effective inactivation of SARS-CoV-2

Controlling the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a long-standing challenge. The cationic phenylene ethynylene polymers were synthesized which lead to strong inactivation of the virus of SARS-CoV-2 at the wavelengths they absorb.^[1] The cationic phenylene ethynylene polymers combine with viral proteins that produce singlet oxygen and ROS by light-activated, ultimately damage and inactivate the virus of SARS-CoV-2. To our delight, the cationic phenylene ethynylene polymers show nearly no toxicity to mammalian cells or human skin. The cationic phenylene ethynylene polymers could be used as the active agent in masks or disinfecting solutions and longlasting surface coatings that can be useful in preventing infections and the spreading of this deadly virus.

Figure 1. The cationic phenylene ethynylene polymers highly effective inactivate SARS-CoV-2 at near-UV and visible light

• PDT and synchronous anticancer

Photodynamic therapy (PDT) has shown great promise as a next-generation cancer therapeutic strategy due to its minimal invasiveness, negligible observed drug resistance and real-time monitoring of therapeutic efficacy. The dual-functional photosensitizer of TPCI can not only kill cancer cells efficiently but also self-report the therapeutic response in real time.^[2] The photosensitizer TPCI can efficiently induce carcinoma cells death by generating reactive oxygen species upon appropriate irradiation. Meanwhile, the weakly fluorescent exist in living cells before irradiation and lights up the nuclei concomitantly during cell death upon irradiation.

Figure 2. The dual-functional photosensitizer of TPCI was used in PDT and synchronous anticancer

• 3D Printing

3D-Printed photoactive composites of poly(3-hexylthiophene-2,5-diyl) (P3HT) for light sensors was reported that prepare by dispersing semiconducting polymer nanowires into epoxy or acrylic resins, followed by curing with UV light and converting visible light to an electric current signal.^[3] The composite precursors before curing had been used for 3D-printed light sensors to create to form rigid photoactive structures with high mechanical moduli and strengths.

Figure 3. 3D-Printed photoactive composites

• Photocatalytic hydrogen

The most promising strategies for sustainable energy production is that photocatalytic splitting of water into H₂ and renewable sunlight. The bifunctional FeX@Zr6-Cu MOFs^[4] were prepared by combining cuprous photosensitizing linkers (Cu-PS) with catalytically active [Fe]II centers for highly effective visible-light-driven H₂ evolution. Given the proximity between Cu-PS and [Fe] moieties, the MOFs were exceptionally high photocatalytic H₂ evolution, with turnover numbers up to 33700 and turnover frequencies up to 880 h⁻¹.

Figure 4. Cu Photosensitizers for photocatalytic hydrogen

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References:

1. Monge F. A.; et al. Highly effective inactivation of SARS-CoV‑2 by conjugated polymers and oligomers. ACS Appl. Mater. Interfaces 2020, 12(50): 55688-55695.
2. Gao Y.; et al. A dual-functional photosensitizer for ultraefficient photodynamic therapy and synchronous anticancer efficacy monitoring. Adv. Funct. Mater. 2019, 29(32): 2673-2685.
3. Shan X.; et al. 3D-Printed photoactive semiconducting nanowire–polymer composites for light sensors. ACS Appl. Nano Mater. 2020, 3(2): 969-976.
4. Pi Y.; et al. Metal−organic frameworks integrate Cu photosensitizers and secondary building unit-supported Fe catalysts for photocatalytic hydrogen evolution. J. Am. Chem. Soc. 2020, 142(23): 10302-10307.