Processable photonic polymers with controllable properties

A series of polyethers consisting of a conjugated segment connected with a nonconjugated spacer were synthesized and characterized. On the basis of the chemical structure of the conjugated moiety, controllable light emission was obtained. The thermal properties were influenced from the structure of the conjugated segment, the type of substituents used, and the length of the flexible spacer used. Additionally, coil‐rod‐coil block copolymers having conjugated segments as the rod block were prepared with atom transfer radical polymerization of α,ω‐modified conjugated oligomers. The optical properties of these copolymers were examined with respect to their aggregation behavior. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2485–2491, 2003     

Novel photo‐crosslinkable liquid crystalline polymers containing vanillylidene cycloalkanones and azobenzene units

Two series of novel liquid crystalline photo‐crosslinkable bis(vanillylidene‐azobenzene) cycloalkanone containing polymers, namely poly(vanillylidene alkyloxy‐4,4′‐azobenzenedicarboxylic ester)s, have been synthesised from bis[m‐hydroxyalkyloxy(vanillylidene)cycloalkanone] (m = 6, 8, 10) with azobenzene dicarbonylchloride by solution polycondensation method at ambient temperature. Polymers with varying spacer lengths have been synthesised and characterised by spectroscopic techniques. These variations have been correlated with the thermal properties and transition temperatures. Thermal transitions were analysed by differential scanning calorimetry (DSC) and the mesophases were identified by hot stage optical polarised microscopy (HOPM). All of the polymers were found to exhibit liquid crystalline properties. Transition temperatures were observed to decrease with increasing spacer length. The thermogravimetric analysis reveals that all of the polymers were stable up to 280°C undergo two‐stage decomposition. Using the UV–visible photolysis studies we investigated the simultaneous behaviour of reactivity rates of crosslinking in the vanillylidene unit and isomerisation caused by the azobenzene unit in the photo‐crosslinkable main chain liquid crystalline polymers. The photolysis of liquid crystalline bis(vanillylidene)cycloalkanone‐based polymers reveals that there are two kinds of photoreactions in these systems: the EZ photoisomerisation of azobenzene unit and 2p+2p addition by vanillylidene units. The EZ photoisomerisation in the liquid crystal phase disrupts the parallel stacking of the mesogens, resulting in the transition from the liquid crystal phase to isotropic phase. The photoreaction involving 2p+2p addition of the bis(vanillylidene)cycloalkanone units in the polymers results in the conjoining of the chains. The cyclopentanone polymers exhibited a faster rate of photolysis than the cyclohexanone polymers.     

A Study on Liquid Hybrid Material for Waveguides—Synthesis and Property of PSQ‐Ls for Waveguides

Silicate‐based inorganic‐organic hybrid polymer systems have many unique properties including thermal stability and photo‐stability, chemical resistance with the combination of tunable optical properties. Two kinds of new UV‐patternable hybrid materials PSQ‐Ls were synthesized by a sol‐gel process at room temperature, which can be used for low cost fabrication of optical waveguides. Thick films (up to 8.31 µm) can be coated by a single spin‐coating process without any cracking and the average surface roughness (Ra), detected by atomic force microscopy (AFM), is below 0.5 nm. The optical properties (refractive index, birefringence, and optical loss at 1310 nm and 1550 nm, respectively) of the PSQ‐Ls films are investigated by a prism coupler. The refractive index of PSQ‐Ls can be exactly tuned from 1.4483 to 1.5212 by blending PSQ‐LH (n_TE=1.5212 @ 1310 nm) and PSQ‐LL (n_TE=1.4483 @ 1310 nm). The maximum refractive index contrast is about 4.8%. After post‐baking, birefringences of the films are below 0.0005 and optical losses are about 0.2 dB · cm^?1 at 1310 nm, 0.7 dB · cm^?1 at 1550 nm, respectively. Furthermore, the PSQ‐Ls films also show outstanding thermal stability in air atmospheres.     

Azobenzene‐containing LC polymethacrylates highly photosensitive in broad spectral range

Two photosensitive chiral liquid crystalline azobenzene‐containing polymethacrylates having different length of flexible spacer connecting chromophores with backbone were synthesized and their phase behavior and photo‐optical properties were studied. Both polymers consist of lateral methyl substituents in ortho‐position of azobenzene chromophores providing high photosensitivity even in red spectral region as well as high thermal stability of photoinduced Z‐form of azobenzene chromophores. It is shown, that smectic phase (SmA*) formation in films of polymer with longer spacer predetermines its quite unusual spectral response to UV and subsequent visible light actions. The SmA* phase promotes spontaneous homeotropic alignment of azobenzene chromophores in polymer films. UV‐irradiation induces not only E‐Z isomerization but also results in disruption of homeotropic alignment, whereas subsequent visible light action enables to obtain films with the low degree of chromophores orientation. The photo‐orientation phenomena under the action of polarized light of different wavelength on polymer films were studied. The possibility of using red polarized light of moderate intensity for optical photorecording on polymer films is demonstrated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2962–2970     

Photo‐Oxidation of sPP/Organoclay Nanocomposites

Photo‐oxidation of syndiotactic polypropylene–sPP/organoclay nanocomposites was performed. Nanocomposites were prepared in situ by melt compounding of sPP, compatibilizer (iPP grafted with maleic anhydride–iPP‐g‐MAN) and organoclay filler ME C18 (modified with octadecyl ammonium chains in intergaleries of layered silicate, of which silicate layers (about 1 nm thin) were exfoliated). The influence of ME C18 nanoparticles alone (in content region 1 to 15 wt%) and together with compatibilizer iPP‐g‐MAN on the photostability of the sPP nanocomposite was studied. It was found that the silicate ME C18 nanoparticles alone catalyze the photooxidation and shorten the induction period of photo‐oxidation to one fourth (at the content of 5 wt% of ME C18) in comparison with unfilled sPP) and the presence of compatibilizer supports the photo‐oxidation of sPP nanocomposite. The ME C18 nanoparticles decrease the efficiency of UV stabilizers. The rate of photo‐oxidation of sPP/clay nanocomposite after the induction period is significantly higher than unfilled sPP. The mechanism of photo‐oxidation is discussed.     

Dual‐curable fluorinated poly(methacrylate) copolymers for optical adhesives

In pursuit of photo‐curable adhesive for optical communication, dual‐curable acrylic oligomers (AOs) having alkoxy silane group, fluorine atoms and vinyl group as a pendent group were synthesized by two‐stage reactions. The isocyanate group containing oligomers were firstly synthesized via radical polymerization of acrylic monomers, and followed by urethane reaction with 2‐hydroxy ethyl methacrylate. The dual curing behaviors, e.g. thermal and photo‐cure, were studied by using photo‐differential scanning calorimetry (DSC) and real‐time IR. An optimum adhesive formulation, based on AO (15 g), epoxy acrylate (80 g), isobonyl methacrylate (17 g) and photo‐initiator (3 g), was obtained. As the content of AO was increased in the optical adhesive formulation, refractive index decreased but transmittance increased due to the increase in fluorine content. The optical transmittance at the range of 1.3 to 1.55 μm was higher than 90%. The addition of colloidal silica with the earlier mentioned formulation was helpful in decreasing crosslinking volume shrinkage and the increasing of glass fiber adhesion. The required properties for the optical adhesive, including chemical resistance and thermal resistance, dimension stability, etc. were also investigated. Copyright © 2005 John Wiley & Sons, Ltd.     

New rod-coil block copolymers consisting of terfluorene segments and electron transporting units as the flexible blocks

A series of new rod-coil block copolymers having a well-defined terfluorene unit as the rigid segment with three different electron transporting moieties as the flexible part, such as side chain oxadiazole (TFPOXD), side chain quinoline (TFPQN) and a molecule containing two oxadiazole rings in the side chain (TFPDOXD), were synthesized using the atom transfer radical polymerization (ATRP) technique. All the synthesized copolymers were extensively examined with respect to their optical properties as pristine films, upon thermal annealing (200 °C for 30 min in air) and photo-oxidation treatment in air. Thermal annealing of the block copolymers resulted in stable blue light emission from TFPOXD and TFPDOXD while TFPQN showed the appearance of the undesired 520 nm emission band. In addition, TFPOXD does not exhibit the low-energy emission band at 520 nm after photo-oxidation under prolonged diffuse UV radiation at ambient atmosphere, despite the fluorenone formation on the terfluorene segment, in contrast to all the other copolymers.     

Removal of atrazine from water using an iron photo catalyst supported on activated carbon

Atrazine is a systemic triazine herbicide, which has been classified as an endocrine disrupting pesticide of hormones and the reproductive systems of humans. Moreover, atrazine was recently considered as a potential carcinogen by several reports. The aim of this work was to synthesize and to evaluate an iron catalyst supported on activated carbon to remove atrazine from water. Five different treatment schemas were evaluated: (1) adsorption with the photocatalyst’s support alone, (2) adsorption with the supported photocatalyst alone, (3) adsorption coupled to heterogeneous Fenton reaction, (4) adsorption coupled to heterogeneous advanced oxidation with UV light and (5) adsorption coupled to heterogeneous photo assisted Fenton reaction. The photocatalyst synthesized, via the incipient wet impregnation method, showed 1176 ± 24 m²/g of Langmuir area and 1.6 % wt/wt of iron content. After 120 min of reaction time, total removal efficiencies in the treatment schemas using the photocatalyst ranged from 70 % (mainly adsorption with the photocatalyst alone) to 96 % (Adsorption and heterogeneous photo assisted Fenton reaction). The heterogeneous photo assisted Fenton reaction was the fastest and most efficient treatment schema, with results better than that reported for similar materials. The adsorption data was fitted to a kinetic model of pseudo-second order and the results of advanced oxidation process were fitted to a kinetic model of fractional order.     

Soluble rigid–flexible polyethers containing bis(biphenyl)anthracene or bis(styryl)anthracene units in the main chain for light-emitting applications

New rigid–flexible polyethers containing bis(biphenyl)anthracene or bis(styryl)anthracene units in the main chain were synthesized and characterized by viscosimetry, thermal and mechanical analysis, NMR, UV-vis, and luminescence spectroscopy. The polyethers containing bis(styryl)anthracene units in the main chain form free-standing films either from solution casting or after melt pressing at temperatures where they are thermally stable. The length of the flexible spacer influences the thermal and mechanical behavior of these polymers. The isotropization temperature as well as the glass transition temperature show an odd–even effect depending on the spacer segment length. Films with high modulus at room temperature and glass transition temperatures in the range 74–103°C were obtained using dynamic mechanical analysis. These polymers show bright-yellow photoluminescence with maximum at 580 nm in solution. In the solid state, the luminescence maximum is either red or blue shifted depending on the number of the methylene units in the aliphatic segment. The polyethers containing bis(biphenyl)anthracene units in the main chain are blue-light-emitting polymers with photoluminescence maxima at 435 and 455 nm in solution. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3826–3837, 1999     

Synthesis and properties of soluble,fluorescent polyesters and polyethers with substituted m‐terphenyl segments in the main chain

A new series of rigid polyesters and semiflexible polyethers were synthesized from 4,4″‐dihydroxy‐5′‐phenyl or anthracenyl‐m‐terphenyl. The polymers were characterized by viscometry, Fourier transform infrared, NMR, X‐ray, differential scanning calorimetry, thermomechanical analysis, thermogravimetric analysis, ultraviolet–visible, and luminescence spectroscopy. The polyesters were amorphous, whereas some of the polyethers showed a low degree of crystallinity. All the polymers displayed an enhanced solubility even in 1,1,2,2‐tetrachloroethane and tetrahydrofuran. The glass‐transition temperatures were 123–146 °C for the polyesters and 45–117 °C for the polyethers. The polymers were stable up to 213–340 °C and afforded anaerobic char yields of 36–62% at 800 °C. Their optical properties were investigated both in solution and in the solid state. They showed ultraviolet fluorescence, violet‐blue fluorescence, or both with emission maxima at 333–487 nm. The polymers with anthracenyl pendent groups exhibited higher fluorescence quantum yields and emission maxima redshifted compared with the corresponding polymers with phenyl pendent groups. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2381–2391, 2000     

Optical Properties and Photo‐Oxidation of Tetraphenylethene‐Based Fluorophores

We report the optical properties of tetraphenylethene (TPE) and other TPE derivatives functionalised with an octyl group (TPE‐OCT) and polyethyleneglycol group (TPE‐PEG) in the side chain. We compared TPE‐OCT and TPE‐PEG with TPE in both organic solvents and under aqueous conditions. All materials exhibit aggregation‐induced emission, however, uncommonly, TPE‐PEG seems to aggregate in aqueous solution with enhanced photoluminescence quantum efficiency (PLQE) relative to that in organic solvents. All three materials can be photo‐oxidised in solution to their diphenylphenanthrene derivative by irradiation with UV light (at both ≈1 and ≈5 mW cm^?2), with a subsequent enhancement in PL efficiency. The electron‐donating ether group increases the rate of oxidation relative to bare TPE and also photo‐oxidation was shown to be solvent and concentration dependent. Finally, photo‐oxidation was also demonstrated in the aggregate state.     

Qualitative evaluation of microfibrillated cellulose using the crill method and some aspects of microscopy

It has been a challenge to develop rapid online characterisation techniques for nanocellulose given the fibrillar structure of the nanoparticles. The crill optical analyser uses optical response signals in the infrared (IR) and ultraviolet (UV) wavelength ranges to evaluate the particle size properties of micro/nanofibrillar cellulosic materials. In this work, the crill analyser was used to measure the projected areas of UV and IR light sources by measuring the light blocked by nanocellulosic particles. This work uses the crill methodology as a new, simplified technique to characterise the particle size distribution of nanocellulosic material based on chemi-thermomechanical pulp (CTMP), thermomechanical pulp (TMP), and sulphite pulp (SP). In the first part, hydrogen peroxide pretreatment of CTMP and TMP in a wing mill refiner followed by high-pressure homogenisation to produce microfibrillated cellulose (MFC) was evaluated using the crill method. In the second part, TEMPO oxidation of CTMP and SP combined with high-shear homogenisation to produce MFC was studied using the crill method. With 4 % hydrogen peroxide pretreatment, the crill values of the unhomogenised samples were 218 and 214 for the TMP and CTMP, respectively, improving to 234 and 229 after 18 homogenisation passes. The results of the TEMPO method indicated that, for the 5 mmol NaClO SP-MFC, the crill value was 108 units at 0 min and 355 units after 90 min of treatment, a 228 % improvement. The CTMP and TMP fibres and the MFC were freeze dried and fibrillar structure of the fibres and microfibrils was visualised using scanning electron and transmission electron microscopy.     

Influence of thermoplastic spacer on the mechanical,electrical, and thermal properties of carbon black filled epoxy adhesives

A new approach of mimicking the selective localization mechanism of conductive filler into one phase of immiscible polymer blend system is proposed here, where a moderate fine of polymethylmethacrylate (PMMA) powder is prepared and used as the spacer in the carbon black (CB) filled epoxy adhesives system that can be applied at room temperature. The main purpose of PMMA‐spacer is to promote the formation of conductive networks via aiding the 3D self‐assembly of CB filler, selectively in the continuous phase of epoxy. PMMA‐spacer content ranged from 10, 20, 30, 40, and 50 vol.% were investigated under electrical, mechanical, and thermal properties for both unfilled and 15 vol.% CB filled system. With the incorporation of 10 vol.% PMMA‐spacer, the filled system shows promising improvement in electrical conductivity, with three order of magnitude increment at 15 vol.% CB loading. Toughening mechanism of epoxy was observed, where crack deflection upon the PMMA‐spacer is observed under scanning electron microscopy characterization and agreed by fracture toughness calculation. Thermal stability and coefficient of thermal expansion were improved at the minimum addition of PMMA‐spacer content, at 10 vol.%, while a small reduction in flexural strength is observed because of the poor interface interaction between the PMMA‐spacer and epoxy matrix. Interestingly, a limited interaction between the PMMA‐spacer with epoxy at the curing temperature of 100°C is observed, indicating the solubility of PMMA‐spacer in epoxy before crosslinking process occurred. Copyright © 2016 John Wiley & Sons, Ltd.     

Photo‐optical properties and photo‐orientation phenomena in an immiscible blend of cholesteric copolymer with azobenzene‐containing polymer

Novel side chain liquid crystalline polymer blends containing immiscible non‐chiral and cholesteric polymers were prepared. A non‐chiral polymer was used containing azobenzene side groups capable of E–Z photoisomerization. Phase behaviour and miscibility properties of the blends were studied. Thin films of the blends were prepared by spin‐coating; it was shown that just after preparation these films are optically isotropic and homogeneous. Photo‐ and chiro‐optical properties of the films as well as photo‐orientation phenomena induced by the action of polarized light were investigated. It was found that the photo‐optical behavior of these films is rather complicated and considerably different from the properties of both individual components. This difference is associated with the strong influence of blend morphology on the photo‐optical properties.     

Synthesis and mesomorphic properties of chiral liquid crystal dimers derived from azobenzene and substituted naphthol

Symmetrical liquid crystal dimers bis{2-alkyl-(S)-(+)-2-(6-[4-4′-decyloxyphenylazo)-benzoyloxy]-2-naphthyl)propinate} have conveniently been designed, synthesised and their mesomorphic properties were investigated. These dimers possess two identical mesogenic units with each of them attached to the terminal end of a flexible spacer (–C _n H_2n ; where n = 6–10). The respective mesogenic unit was made up from a naphthyl ring attached to the alkyloxylated azobenzene via the ester (COO–) bond. The chiral moiety attached to the 6-position of the naphthyl ring possesses a terminal carboxylic group COO– which linked up the mesogenic unit and the spacer. The thermal and optical properties for the ultimate compounds at different temperature were studied explicitly with the aids of differential scanning calorimetry and polarising optical microscopy. All dimers exhibit unambiguously the monotropic nematic and smectic A phases. The homeotropic alignment of the molecules within the anisotropic region was further confirmed through the application of homogeneously treated cell.     

Metal free synthesis of 1‐azaspiro[4.4]nonane‐3‐one system via reactions of nitrones with 1,1‐disubstituted allenes

In the cycloaddition reaction between fluorenone N‐aryl nitrones and 1,1‐disubstituted allenes, the initially formed cycloadduct underwent facile [1,3] shift to give 1′‐phenylspiro[fluorene‐9,2′‐pyrrolidin]‐4′‐ones. Although 1′‐phenylspiro[fluorene‐9,2′‐pyrrolidin]‐4′‐ones are stable in solid state, a few of them underwent facile aerial oxidation in solution to give the corresponding 1′‐phenylspiro[fluorene‐9,2′‐pyrrolidine]‐4′,5′‐diones in excellent overall yields.     

Structure–property relationship of photoactive liquid crystalline polyethers containing benzylidene moiety

A series of main chain photoactive liquid crystalline polyethers, containing rigid bisbenzylidene photoactive mesogen and flexible methylene spacers, were synthesized by polycondensation of bisbenzylidene diols and dibromoalkanes. The polyethers were characterized with ¹H NMR, gel permeation chromatography (GPC), differential scanning calorimeter (DSC), thermo gravimetric analyzer (TGA), and polarized light optical microscopy. The individual and combined effects of spacer length and number of methoxy substituents on mesogenic and photoactive properties were investigated. Both first order and second order transition temperatures decreased with increased spacer length and the number of substituents. The combined effect of spacers and substituents drastically reduced the transition temperatures. All monomers and polymers showed mainly the smectic mesophase. In a few cases, nematic droplets along with the smectic phase were observed. The width of the liquid crystalline phase reduced with an increasing number of methoxy substituents on mesogenic unit. Variation of spacer length has a negligible effect on photocycloaddition. However, steric hinderance caused by the substituents decreased the photoactivity as the number of substituents increased. Total energies of crosslinked dimers calculated from modeling studies supported the above findings. Intermolecular photocycloaddition was also confirmed by photoviscosity measurement. The refractive index change was found to be in the range of 0.017–0.031. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2143–2155, 2009     

Application of thermovision for estimation of the optimal and safe parameters of the whole body cryotherapy

Exposure to the extreme low temperatures, ranging between ?60 and ?140 °C, has many beneficial effects on the human body what is exploited for example in sport medicine, for treatment of locomotory system diseases or even some psychiatric disorders. To insure the safe treatment in a cryochamber, careful planning of the procedure and proper qualification of patients, is required. Cardiovascular system, especially skin vasculature plays the major role of the body response to the extreme cold. The changes in skin blood flow are reflected in changes of the temperature distribution. Therefore, the thermal imaging, which allows to analyze the temperature distribution on the human body, may be successfully exploited to examine the influence of extremely low temperatures on the skin vascular system. The aim of this work was to examine the temperature, blood pressure, and heart rate changes after the whole body cryotherapy in healthy subjects to determine the safety conditions of the treatment. 480 healthy students of the Wroc?aw University School of Physical Education were divided into two groups (each 240 persons). All subjects were exposed for 1–3 min to the extremely low temperatures: ?60, ?100, ?120, and ?140 °C. In one group, the thermograms were recorded before and 5 and 30 min after the cryotherapy by means of ThermoVision A20 M thermal camera. In the other one, heart rate and blood pressure were measured before and 5 min after the cryotherapy. It was demonstrated that 3-min exposure in the cryochamber and the temperature ?120 °C are the optimal and safe cryotherapy parameters.     

A novel photobleachable polysilane copolymer for optical waveguide fabrication

Poly(methylphenylsilane)‐poly(benzylmethacrylate) (PMPS‐PBzMA) block copolymer was prepared by photopolymerization of benzylmethacrylate (BzMA) monomer using PMPS as a macromolecular photo‐radical initiator. Its application as a photobleachable polymer material for optical waveguide fabrication was investigated. By changing weight ratios of BzMA to PMPS during polymerization, the obtained PMPS‐PBzMA showed different photo‐induced refractive changes. PMPS‐PBzMA proved to have good photosensitivity, optical properties, and thermal stability. A multimode PMPS‐PBzMA optical waveguide was achieved, with a propagation loss of 1.0 dB/cm at 1310 nm. Copyright © 2009 John Wiley & Sons, Ltd.     

Photoluminescent behavior of poly(3‐hexylthiophene) derivatives with a high azobenzene content in the side chains

A series of polythiophene derivatives with substantially higher azobenzene contents in the side chains were prepared via copolymerization of 3‐hexylthiophene with four different types of 4‐((4‐(phenyl)azo)phenoxy)alkyl‐3‐thienylacetate. The alkyl spacers with different lengths, i.e. butyl, hexyl, octyl and undecyl groups were used between the azobenzene group and the thiophene ring. The compositions, structures and thermal properties of these polythiophene derivatives were characterized. The structural dependence of photoluminescent emission, photochromic behavior of these copolymers were systematically studied and compared with poly(3‐hexylthiophene). The results show that the azobenzene substitution renders the polythiophene some interesting optical properties that can be modulated by UV light irradiation. In the azobenzene modified polythiophene, the intensity of photoluminescent emission associated with the conjugated polythiophene main chain was found to decrease significantly upon UV irradiation. The finding suggests that the photo‐induced trans‐cis isomerization of the azobenzene pendant groups has a significant effect on photoluminescent emission, particularly when short spacers are used between azobenzene groups and the main chain. However, the effect becomes less prominent when longer spacers are used between the azobenzene group and the main chain. Furthermore, UV irradiation of the copolymers also resulted in an increase in intensity and broadening of bandwidth for the absorption peak associated with the polythiophene backbones. Again the magnitude of intensity changes upon UV irradiation were found to be dependent on the spacer length between the azobenzene group and polythiophene main chain. Copyright © 2005 John Wiley & Sons, Ltd.