Special Issue "Photo-Responsive Polymers"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (30 June 2017).

Special Issue Editors

Prof. Dr. John T. Sheridan
Website
Guest Editor
UCD School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Belfield, Dublin 4, Ireland
Interests: photo-polymeristion; photo-polymers; dye sensitised polymers; PQ/PMMA; optical applications of polymers including: holography, waveguides, gratings
Special Issues and Collections in MDPI journals
Prof. Dr. Yanlei Yu
Website
Guest Editor
Department of Materials Science, Fudan University, 220 Handan Road, Shanghai 200433, China
Interests: photoresponsive liquid crystal polymers; photodeformation; photoresponsive interfacial materials; optofluidic actuation

Special Issue Information

Dear Colleagues,

At the intersection of optical physics, dye and polymer chemistry and material and surface engineering lies the exciting area of photo-responsive polymers. The optical inspection/characterisation of materials and components and the application of polymers to manipulate light all have long and not unrelated histories.  The topics that this Special Issue addresses encompasses the study, modelling and design of photo-polymer processes, materials and their applications. While the individual research areas and disciplines associated with photo-sensitive polymers are well-established, interest in the area itself is increasing and it is fair to describe it as a “hot topic”. In part this is driven by the successful development of UV curable adhesives, photoalignment and photopatterning, photomechanical effects, the production of holographic element for electromagnetic and matter waves and the generation of novel biomedical devices. It arises due to the ongoing development of new materials, allowing novel applications to be found. In some cases, such materials are easily more used, e.g., processed/cured, while in others they may be biocompatible or reproduce physical or biological function.  Recent advances have also been driven by the need to find new ways to solve existing technological and scientific challenges. Such situations may require some particular combination of material performance characteristics, e.g., transparency, permeability, weight, compatibility, and/or low cost. The design and development of new photo-sensitive materials requires a fundamental understanding of the material properties required and the intended uses. The general aim of this review is to provide insights into the breadth of current research and developments in this area.

Prof. Dr. John T. Sheridan
Prof. Dr. Yanlei Yu
Guest Editors

Manuscript Submission Information

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Keywords

  • Photopolymer
  • Photosensitive
  • Photocurable
  • Dye
  • Photosensitiser
  • Holography
  • Photochemical
  • Photomechanical
  • Photoalignment
  • Photopatterning
  • Photochromic
  • Light-driven

Published Papers (14 papers)

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Research

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Open AccessArticle
Spontaneous Formation of Fractal Aggregates of Au Nanoparticles in Epoxy-Siloxane Films and Their Application as Substrates for NIR Surface Enhanced Raman Spectroscopy
Polymers 2017, 9(10), 507; https://doi.org/10.3390/polym9100507 - 13 Oct 2017
Cited by 3
Abstract
We present a facile, inexpensive route to free-standing, thermo-mechanically robust and flexible epoxy-siloxane substrates embedded with fractal aggregates of Au nanoparticles, and demonstrate their efficiency as substrates for surface enhanced Raman spectroscopy (SERS) at NIR wavelengths. The metallodielectric films are prepared by generating [...] Read more.
We present a facile, inexpensive route to free-standing, thermo-mechanically robust and flexible epoxy-siloxane substrates embedded with fractal aggregates of Au nanoparticles, and demonstrate their efficiency as substrates for surface enhanced Raman spectroscopy (SERS) at NIR wavelengths. The metallodielectric films are prepared by generating Au nanoparticles through the in-situ reduction of gold (III) chloride trihydrate in epoxypropoxypropyl terminated polydimethyl siloxane (EDMS). The metal nanoparticles spontaneously aggregate into fractal structures in the colloid, which could then be drop-cast onto a substrate. Subsequent UV-initiated cationic polymerization of epoxide moieties in EDMS transforms the fluid colloid into a thin, free-standing film, which contains a dense distribution of fractal aggregates of Au nanoparticles. We used electron and optical microscopy as well as UV–Vis–NIR spectrometry to monitor the evolution of nanoparticles and to optically and structurally characterize the resulting films. Raman spectroscopy of the chromophore Eosin Y adsorbed onto the metallodielectric films showed that they are excellent SERS substrates at NIR excitation with an enhancement factor of ~9.3 × 103. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Photochromic Polyurethanes Showing a Strong Change of Transparency and Refractive Index
Polymers 2017, 9(9), 462; https://doi.org/10.3390/polym9090462 - 20 Sep 2017
Cited by 10
Abstract
Photochromic polymers have been studied as rewritable systems for optical elements with tunable transparency in the visible and refractive index in the NIR. Six diarylethene monomers have been synthesized to give thin films of photochromic polyurethanes. The absorption properties of the monomers in [...] Read more.
Photochromic polymers have been studied as rewritable systems for optical elements with tunable transparency in the visible and refractive index in the NIR. Six diarylethene monomers have been synthesized to give thin films of photochromic polyurethanes. The absorption properties of the monomers in solution and of the corresponding polymeric films have been evaluated showing that a transparency contrast in the visible spectrum of the order of 10 3 can be obtained by a suitable choice of the chemical structure and illumination wavelength. The change in the refractive index in the NIR have been determined by ellipsometry showing changes larger than 10 2 . A trend of this variation with the absorption properties has been also highlighted. Fresnel lenses working on the basis of both a change of the transparency and the refractive index (amplitude and phase) have been demonstrated. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Light-Up of Rhodamine Hydrazide to Generate Emissive Initiator for Polymerization and to Afford Photochromic Polypeptide Metal Complex
Polymers 2017, 9(9), 419; https://doi.org/10.3390/polym9090419 - 05 Sep 2017
Cited by 1
Abstract
Ring-opening polymerization (ROP) of cyclic peptide monomer of γ-propargyl-l-glutamate N-carboxyanhydride (PLG–NCA) was originally initiated by non-emissive, ring-close rhodamine 6G hydrazide (R-C). However, instantaneously after adding PLG–NCA to R-C, the spirolactam ring of R-C was opened by PLG–NCA, rendering emissive, ring-open R-O to initiate [...] Read more.
Ring-opening polymerization (ROP) of cyclic peptide monomer of γ-propargyl-l-glutamate N-carboxyanhydride (PLG–NCA) was originally initiated by non-emissive, ring-close rhodamine 6G hydrazide (R-C). However, instantaneously after adding PLG–NCA to R-C, the spirolactam ring of R-C was opened by PLG–NCA, rendering emissive, ring-open R-O to initiate ROP of PLG–NCA. The emissive R-O moiety therefore produced fluorescent R–PLG with aggregation-induced emission (AIE) properties. Moreover, R–PLG was found to exhibit photochromic properties with good fatigue resistance and long lifetime when forming metal complexes with Sn(II) and Fe(III). In the dark, irradiated metal complexes slowly (~50 min) restored to the initial state. This research provides foundation for the development of new photochromic materials with long lifetime. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Optimization of Photopolymer Materials for the Fabrication of a Holographic Waveguide
Polymers 2017, 9(9), 395; https://doi.org/10.3390/polym9090395 - 26 Aug 2017
Cited by 10
Abstract
In this work, we present a method of manufacturing an optical see-through display based on a holographic waveguide with transmission holograms that couple the incident light between air and the glass substrate, accomplishing total internal reflection. The holograms (slanted transmission gratings with a [...] Read more.
In this work, we present a method of manufacturing an optical see-through display based on a holographic waveguide with transmission holograms that couple the incident light between air and the glass substrate, accomplishing total internal reflection. The holograms (slanted transmission gratings with a spatial frequency of 1700 lines/mm) were recorded on a polyvinyl alcohol acrylamide (PVA/AA) photopolymer. We will also show that the addition of N,N′-methylene-bis-acrylamide (BMA) to the composition of the photopolymer allows the achievement of the index modulations necessary to obtain high diffraction efficiencies in non-slanted diffraction gratings of 1000 and 2200 lines/mm, and also in slanted gratings of 1700 lines/mm (which are the base of the optical system proposed). Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Light-Driven Liquid Crystal Circular Dammann Grating Fabricated by a Micro-Patterned Liquid Crystal Polymer Phase Mask
Polymers 2017, 9(8), 380; https://doi.org/10.3390/polym9080380 - 21 Aug 2017
Cited by 6
Abstract
As one of the diffractive optical elements, circular Dammann grating has shown its excellent versatility in practical applications. The electrically switchable Dammann grating has been extensively investigated; however, the research on the optically tunable circular Dammann grating has received less attention and reports [...] Read more.
As one of the diffractive optical elements, circular Dammann grating has shown its excellent versatility in practical applications. The electrically switchable Dammann grating has been extensively investigated; however, the research on the optically tunable circular Dammann grating has received less attention and reports on this subject have been insufficient in the past decade. In this paper, three-order and eight-order binary-phase liquid crystal circular Dammann gratings with two mutually orthogonal photo-induced alignments in every two adjacent alignment domains, fabricated by a micro-patterned liquid crystal polymer phase mask, are proposed to generate annular uniform-intensity patterns in the far field. A simple maskless optical tuning of an eight-order liquid crystal circular Dammann grating is demonstrated by controlling the polarization of an ultraviolet light as well as the energy dose. The proposed liquid crystal circular Dammann gratings with high efficiencies and desirable uniformities exhibit outstanding optical as well as electrical tunabilities, enabling the widespread prospective applications in adaptive photonic chips stimulated flexibly by only light or by the combination of light and electric field. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Correlation-Based Multiplexing of Complex Amplitude Data Pages in a Holographic Storage System Using Digital Holographic Techniques
Polymers 2017, 9(8), 375; https://doi.org/10.3390/polym9080375 - 18 Aug 2017
Cited by 4
Abstract
Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. [...] Read more.
Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. However, most of conventional holographic storage systems encode digital data onto the amplitude alone because there are difficulties for modulating and detecting the phase. To solve the difficulties, a holographic storage system using digital holographic techniques has been proposed. With the help of digital holographic techniques, it is possible to modulate and detect the complex amplitude of a signal beam. Moreover, the proposed system can modulate the complex amplitude of a reference beam. In this paper, by making use of the capability, a correlation-based multiplexing with uncorrelated reference beams is demonstrated in the proposed system. Multiple holograms can be recorded in the same volume of a recording medium with no need for mechanical movements. Experimental results show that the proposed system with a correlation-based multiplexing can improve the storage capacity and can utilize the full potential of a recording medium without crosstalk noise stem from the optical setup. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Additives Type Schiff’s Base as Modifiers of the Optical Response in Holographic Polymer-Dispersed Liquid Crystals
Polymers 2017, 9(7), 298; https://doi.org/10.3390/polym9070298 - 21 Jul 2017
Cited by 6
Abstract
Schiff’s bases with specific π-electron system have been synthesized and used as additives in holographic polymer-dispersed liquid crystals. It was observed that these substances modify different parameters such as current intensity, voltage, and diffracted light intensity. In addition, the maximum diffraction efficiency obtained [...] Read more.
Schiff’s bases with specific π-electron system have been synthesized and used as additives in holographic polymer-dispersed liquid crystals. It was observed that these substances modify different parameters such as current intensity, voltage, and diffracted light intensity. In addition, the maximum diffraction efficiency obtained in the reconstruction of the holograms is related to the additive molecule. We propose a relationship between this behavior and the molecular structure of these substances. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Light-Driven Rotation and Pitch Tuning of Self-Organized Cholesteric Gratings Formed in a Semi-Free Film
Polymers 2017, 9(7), 295; https://doi.org/10.3390/polym9070295 - 21 Jul 2017
Cited by 13
Abstract
Cholesteric liquid crystal (CLC) has attracted intensive attention due to its ability to form a periodic helical structure with broad tunability. CLC gratings in open systems are especially promising in sensing and micromanipulation. However, there is still much to learn about the inherent [...] Read more.
Cholesteric liquid crystal (CLC) has attracted intensive attention due to its ability to form a periodic helical structure with broad tunability. CLC gratings in open systems are especially promising in sensing and micromanipulation. However, there is still much to learn about the inherent mechanism of such gratings. We investigate the light-driven rotation and pitch-tuning behaviors of CLC gratings in semi-free films which are formed by spin-coating the CLC mixtures onto planarly photoaligned substrates. The doped azobenzene chiral molecular switch supplies great flexibility to realize the continuous grating rotation. The maximum continuous rotational angle reaches 987.8°. Moreover, dependencies of light-driven rotation and pitch tuning on the dopant concentration and exposure are studied. The model of director configuration in the semi-free film is constructed. Precise beam steering and synchronous micromanipulation are also demonstrated. Our work may provide new opportunities for the CLC grating in applications of beam steering, micromanipulation, and sensing. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Modeling Diffractive Lenses Recording in Environmentally Friendly Photopolymer
Polymers 2017, 9(7), 278; https://doi.org/10.3390/polym9070278 - 12 Jul 2017
Cited by 3
Abstract
The improvements made in diffusion models simulating phase image recording in photopolymers enable the optimization of a wide range of complex diffractive optical elements (DOEs), while the miniaturization of spatial light modulators makes it possible to generate both symmetric and non-symmetric DOEs. In [...] Read more.
The improvements made in diffusion models simulating phase image recording in photopolymers enable the optimization of a wide range of complex diffractive optical elements (DOEs), while the miniaturization of spatial light modulators makes it possible to generate both symmetric and non-symmetric DOEs. In addition, there is increasing interest in the design of new friendly recording materials. In this respect, photopolymers are a promising material due to their optical properties. In this paper, we show a procedure to record diffractive spherical lenses using a nontoxic optimized photopolymer. To achieve this goal, we followed three steps: first, the chemical optimization for DOE recording; second, the recording material characterization to be simulated by a three-dimensional diffusion model; and third, the evaluation of the coverplating for the conservation of the DOE. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessCommunication
A Near-Infrared Light-Responsive Hybrid Hydrogel Based on UCST Triblock Copolymer and Gold Nanorods
Polymers 2017, 9(6), 238; https://doi.org/10.3390/polym9060238 - 20 Jun 2017
Cited by 22
Abstract
We report a near-infrared (NIR) light-responsive hydrogel that is capable of undergoing the gel to sol transition upon 785 nm light exposure based on a photothermal effect. The new hydrogel design relies on loading gold nanorods (AuNRs) in an ABA-type triblock copolymer, namely [...] Read more.
We report a near-infrared (NIR) light-responsive hydrogel that is capable of undergoing the gel to sol transition upon 785 nm light exposure based on a photothermal effect. The new hydrogel design relies on loading gold nanorods (AuNRs) in an ABA-type triblock copolymer, namely P(AAm–co–AN)–b–PDMA–b–P(AAm–co–AN), where P(AAm–co–AN) stands for a random copolymer of acrylamide and acrylonitrile that exhibits an upper critical solution temperature (UCST) in aqueous solution and PDMA is water-soluble polydimethylacrylamide. At solution temperature below UCST, the insoluble P(AAm–co–AN) blocks lead to formation of hydrogel of flower-like micelles. When the hydrogel is exposed to 785 nm NIR light, the absorption due to the longitudinal surface plasmon resonance of loaded AuNRs generates heat that raises the hydrogel temperature above UCST and, consequently, the gel-to-sol transition. The NIR light-triggered release of a protein loaded in the hydrogel was found to display a switchable fashion. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Photo-Induced Vertical Alignment of Liquid Crystals via In Situ Polymerization Initiated by Polyimide Containing Benzophenone
Polymers 2017, 9(6), 233; https://doi.org/10.3390/polym9060233 - 18 Jun 2017
Cited by 7
Abstract
Vertical alignment of liquid crystal (LC) was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA) monomers initiated by polyimide based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 3,3′-dimethyl-4,4′-diaminodiphenyl methane (BTDA-DMMDA PI). The alignment behavior and alignment stabilities were characterized by [...] Read more.
Vertical alignment of liquid crystal (LC) was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA) monomers initiated by polyimide based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 3,3′-dimethyl-4,4′-diaminodiphenyl methane (BTDA-DMMDA PI). The alignment behavior and alignment stabilities were characterized by a polarizing optical microscope (POM), which showed a stable vertical alignment after 12 h of thermal treatment. The chemical structures, morphology, and water contact angles of alignment films peeled from LC cells with and without DA monomers were analyzed by means of a Fourier transform infrared spectrometer (FTIR), a scanning electron microscope (SEM), and a contact angle tester, separately. The results confirmed that the DA monomers underwent self-polymerization and grafting polymerization initiated by the BTDA-DMMDA PI under ultraviolet irradiation, which aggregated on the surfaces of PI films. The water contact angles of the alignment films were about 15° higher, indicating a relative lower surface energy. In conclusion, the vertical alignment of LC was introduced by the low surface free energy of PI films grafted with DA polymer and intermolecular interactions between LC and DA polymers. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Volume Hologram Formation in SU-8 Photoresist
Polymers 2017, 9(6), 198; https://doi.org/10.3390/polym9060198 - 30 May 2017
Cited by 4
Abstract
In order to further understand the mechanism of volume hologram formation in photosensitive polymers, light-induced material response is analyzed in commonly used epoxy-based negative photoresist Epon SU-8. For this purpose, time-resolved investigation of volume holographic grating growth is performed in the SU-8 based [...] Read more.
In order to further understand the mechanism of volume hologram formation in photosensitive polymers, light-induced material response is analyzed in commonly used epoxy-based negative photoresist Epon SU-8. For this purpose, time-resolved investigation of volume holographic grating growth is performed in the SU-8 based host–guest system and in the pure SU-8 material, respectively. The comparison of grating growth curves from doped and undoped system allows us to draw conclusions on the impact of individual components on the grating formation process. The successive formation of transient absorption as well as phase gratings in SU-8 is observed. Influence of exposure duration and UV flood cure on the grating growth are investigated. Observed volume holographic grating formation in SU-8 can be explained based on the generation and subsequent diffusion of photoacid as well as time-delayed polymerization of exposed and unexposed areas. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Review

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Open AccessReview
The Chemistry and Physics of Bayfol® HX Film Holographic Photopolymer
Polymers 2017, 9(10), 472; https://doi.org/10.3390/polym9100472 - 26 Sep 2017
Cited by 36
Abstract
Holographic photopolymers are a new technology to create passive diffractive optical elements by a pure laser interference recording. In this review, we explain the chemistry concepts of light harvesting in an interference pattern and the subsequent grating formation as chemical response. Using the [...] Read more.
Holographic photopolymers are a new technology to create passive diffractive optical elements by a pure laser interference recording. In this review, we explain the chemistry concepts of light harvesting in an interference pattern and the subsequent grating formation as chemical response. Using the example of the newly developed Bayfol® HX film we discuss the reaction-diffusion driven photo-polymerization process for an index modulation formation to create volume phase gratings. Further we elucidate the selection of monomer chemistry and discuss details of the recording conditions based on the concept of exposure dosage and exposure time. Influences ranging from high dosage recording to low power recording are explained and how to affect the desired diffraction efficiency. Finally, we outline and demonstrate the process to mass manufacturing of volume phase gratings. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessReview
A Review of Hologram Storage and Self-Written Waveguides Formation in Photopolymer Media
Polymers 2017, 9(8), 337; https://doi.org/10.3390/polym9080337 - 03 Aug 2017
Cited by 25
Abstract
Photopolymer materials have received a great deal of attention because they are inexpensive, self-processing materials that are extremely versatile, offering many advantages over more traditional materials. To achieve their full potential, there is significant value in understanding the photophysical and photochemical processes taking [...] Read more.
Photopolymer materials have received a great deal of attention because they are inexpensive, self-processing materials that are extremely versatile, offering many advantages over more traditional materials. To achieve their full potential, there is significant value in understanding the photophysical and photochemical processes taking place within such materials. This paper includes a brief review of recent attempts to more fully understand what is needed to optimize the performance of photopolymer materials for Holographic Data Storage (HDS) and Self-Written Waveguides (SWWs) applications. Specifically, we aim to discuss the evolution of our understanding of what takes place inside these materials and what happens during photopolymerization process, with the objective of further improving the performance of such materials. Starting with a review of the photosensitizer absorptivity, a dye model combining the associated electromagnetics and photochemical kinetics is presented. Thereafter, the optimization of photopolymer materials for HDS and SWWs applications is reviewed. It is clear that many promising materials are being developed for the next generation optical applications media. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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