Design of Thermochromic Polynorbornene Bearing Spiropyran Chromophore Moieties: Synthesis, Thermal Behavior and Dielectric Barrier Discharge Plasma Treatment

A new class of thermochromic polynorbornene with pendent spiropyran moieties has been synthesized. Functionalization of norbornene monomers with spirobenzopyran moieties has been achieved using Steglich esterification. These new monomeric materials were polymerized via Ring Opening Metathesis Polymerization (ROMP). In spite of their poor solubility, polynorbornenes with spirobenzopyran exhibited thermochromic behavior due to the conversion of their closed spiropyran moieties to the open merocyanine form. Moreover, these polymers displayed bathochromic shifts in their optical response, which was attributed to the J-aggregation of the attached merocyanine moieties that were associated with their high concentration in the polymeric chain. The surface of the obtained polymers was exposed to atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma system, which resulted in the reduction of the surface porosity and converted some surface area into completely non-porous regions. Moreover, the plasma system created some areas with highly ordered J-aggregates of the merocyanine form in thread-like structures. This modification of the polymers’ morphology may alter their applications and allow for these materials to be potential candidates for new applications, such as non-porous membranes for reverse osmosis, nanofiltration, or molecular separation in the gas phase.


Introduction
Chromogenic polymers are a significant class of smart materials that have been under investigation over the past decade [1][2][3][4][5][6]. The key feature of these materials is their quick and reversible responses to external stimuli. Among these chromogenic materials, photochromic and thermochromic behavior has been observed in various classes of molecules, such as liquid crystals and polymer incorporating smart moieties [1][2][3][4][5][6]. Currently, there is progress in the development of thermochromic polymers ion beam, X-ray, and γ-ray [72][73][74][75]. The use of a plasma system is a versatile and successful strategy for modifying the surface properties or introducing desired chemical groups at the surface of a polymer without affecting its bulk properties [72][73][74][75]. In this study, the surface of the obtained polymers has been subjected to an atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma system in order to examine its effects on the polymers' morphology. Modification of the surface character of the desired polymers allowed for these materials to be potential candidates for new applications, such as non-porous membranes for reverse osmosis, nanofiltration, or molecular separation in the gas phase.

General
All of the chemicals were available from Sigma-Aldrich Chemical Co. (Taufkirchen, Germany) and were used without further purification. Solvents were high performance liquid chromatography (HPLC) grade. ROMP was performed in anhydrous dichlormethane (DCM) >99.8% containing amylene as stabilizer. 1 H NMR and 13 C NMR spectra were recorded at 400 and 100 MHz, respectively, on Bruker 400 MHz ultrashieldTM NMR spectrometer (Bruker, Fällanden, Switzerland), with chemical shifts calculated in Hz, referenced to solvent residues. The IR spectra of the new compounds were recorded on a Jasco FTIR-300 E Fourier Transform Infrared Spectrometer (Jasco, Tokoyo, Japan). Thermogravimetric analysis (TGA) of the polymeric materials was carried out under nitrogen atmosphere at a heating rate 10 • C·min −1 using TA instrument, model SDT600 (New Castle, DE, USA). Differential Scanning Calorimeter (DSC) measurements were performed using a q2000 apparatus with T zero ® techniques from TA instruments (New Castle, DE, USA). The morphological features of the polymers were determined using a "Shimadzu XRD-6000" computerized diffractometer (Shimadzu, Tokoyo, Japan), which consists of α-pw1400/90 stabilized X-ray generator, α-pw1050/70 vertical goniometer, α-pw1995/60 proportional counter, and α-pw1930 electronic panel. Nickel-filter copper radiation with λ = 1.541 Å was used in this investigation. Scanning Electron Microscope (SEM) measurements have been performed using SEM Model Philips XL 30 (FEI company, Hillsboro, OR, USA) with accelerating voltage 30 KV, magnification 10× up to 4000×, and resolution for W. The obtained polymers have been heated up to 180 • C and then cooled to room temperature either as dry or wet sheets. Wettability has been tested in dichloromethane, dimethyl formamide, methanol, chloroform, and aqueous solution.

Dielectric Barrier Discharge (DBD) Plasma System
An atmospheric air-dielectric barrier discharge DBD system was used to generate atmospheric pressure plasma in air [76]. The plasma system consists of two parallel metallic electrodes (the copper cylinder and the stainless steel disc) separated by a 3 mm gape. The upper copper electrode has about a~40 mm diameter and was covered on the bottom by a 2 mm thick dielectric quartz sheet 60 × 60 mm. A high voltage power-supply was connected to the upper electrode, while the lower electrode was grounded. The high voltage electrode was surrounded by a Teflon sleeve for operator safety. The power supply generated sinusoidal waveform signal of 23 kV and 25 kHz. The current and voltage waveforms were recorded using DPO7354 C −3.5 GHz-Tektronix oscilloscope (Tektronix Inc., Beaverton, OR, USA) with a person probe model: 6585 and P6015A −1:1000 Tektronix-high voltage probe, respectively. The treated samples were placed between the two electrodes on the lower stainless steel electrode. Plasma images were captured by Nikon digital camera D3200 (Nikon, Thailand) with AF-S Micro NIKKOR 105 mm lens.  (4) In three necked flask connected with inlet dry argon, a mixture of 1,3,3-trimethyl-2-methylene-5-carboxy-3H-indole (1150 mg, 5 mmol) and 2-hydroxyl-5-nitrobenzaldehyde (970 mg, 6 mmol) in freshly distilled THF (100 mL) was heated under reflux and argon for 10 h. The mixture was cooled down in an ice bath, and the resulting precipitate was filtered off. The pure product was obtained after column chromatography on silica gel using DCM as eluent (R f = 0.32) to yield the chromophore I as a pale yellow powder in (460 mg, 24%). 1 (5) Under an argon atmosphere, a mixture of 1-(2-carboxyethyl)-2,3,3-trimethyl-3H-indol-1-ium bromide (311 mg, 1 mmol) and (167 g, 1 mmol) 2-hydroxy-5-nitrobenzaldehyde was added to 100 mL dry ethyl methyl ketone in the presence of triethyl amine (1 mL), followed by heating under reflux in the dark for 24 h. After the removal of the solvent, the product was washed with ether and the pure product of chromophore 5 was obtained after column chromatography using ethyl acetate-cyclohexane (2:8 then 4:6) as eluent (R f = 0.32). The resulting violet-red powder was recrystallized from ethanol to obtain 136 mg, for a 36.1% yield of yellow-brown powder. 1

Synthesis of Norbornene Monomers
Exo, endo-5-norbornene-2-methanol (2 mmol), chromophores 4 & 5 (0.5 mmol), N,N-dimethylaminopyridine (244 mg, 2 mmol) and 8 mL of CH 2 Cl 2 were placed in a 50 mL round bottom flask. Dicyclohexylcarbodiimide (413 mg, 2 mmol) was dissolved in 2 mL of CH 2 Cl 2 and added to the stirring mixture at 0 • C. The reaction was carried out at room temperature under a nitrogen atmosphere for 18 h. After the removal of the solvent, the crude product was extracted with CH 2 Cl 2 , washed with water, and dried over MgSO 4 . The solvent was removed and the resulting precipitate was then purified using silica column with hexane/ethyl acetate (8:2 then 6:4) solution, (R f = 0.45).

Preparation of Polynorbornene Pendent Chromophore Units
In a 10 mL round bottom flask, the functionalized monomer and 0.5 mL of distilled dichloromethane for every 100 mg of monomer were combined and stirred under a nitrogen atmosphere. In a second flask, the catalyst ([M]/[I] = 100/1) was dissolved in an equivalent amount of dichloromethane and was also purged with nitrogen. The catalyst solution was then added drop wise to the stirring monomer solution, at which time a black sticky solid began to collect on the sides and bottom of the flask. The reaction was stirred for 1-4 h during which time more solid formed. The polymerization was then terminated by the addition of ethyl vinyl ether, and stirred for 15-30 min. The crude polymer was washed with dichloromethane to remove any remaining monomer. The purified polymer was then collected via suction filtration as a reddish sheet.

Monomers Synthesis
Functionalization of norbornene molecules with spiropyran chromophores was proceeded using Steglich esterification, as described in Scheme 2. Exo, endo-5-norbornene-2-mehanol (6) reacted with spiropyrans 4 and 5 in the presence of dicyclohexylcarbodiimide (DCC) and N,N-dimethylaminopyridine (DMAP) for 18 h. Purification of the obtained monomers included extraction with CH 2 Cl 2 , filtration of the dicyclohexylurea (DHU) side product, followed by purification over silica column using hexane/ethyl acetate solution. The structure of chromophores 4 and 5 was confirmed using 1 H and 13 C-NMR spectroscopy. As anticipated, the two spectra displayed some similarities. For example, the two methyl protons of both compounds appeared as singlet between 1.09 and 1.52 ppm, while the aromatic protons appeared as sets of doublets in the range of 6.00 and 8.24 ppm. Differentiation between the two spectra includes the presence of N-CH3 of chromophore 4 at 2.76 ppm, while chromophore 5 exhibited two sets of multiplets corresponding to the methylene spacers. The N-CH2 protons appeared as two multiplets at 3.38 and 3.48 ppm. Moreover, the carboxylic proton of 4 resonated downfield at 12.39 ppm.

Monomers Synthesis
Functionalization of norbornene molecules with spiropyran chromophores was proceeded using Steglich esterification, as described in Scheme 2. Exo, endo-5-norbornene-2-mehanol (6) reacted with spiropyrans 4 and 5 in the presence of dicyclohexylcarbodiimide (DCC) and N,Ndimethylaminopyridine (DMAP) for 18 h. Purification of the obtained monomers included extraction with CH2Cl2, filtration of the dicyclohexylurea (DHU) side product, followed by purification over silica column using hexane/ethyl acetate solution. The structural identity of the new monomeric units was accomplished using NMR spectroscopic analysis. For example, the carboxylic resonance at 12.38 ppm of spiropyran 4 disappeared from the corresponding monomer 7 due to the formation of the ester link. Also, the methylene protons of compound 5 was shifted further upfield upon esterification. Meanwhile, the presence of the new resonances of the norbornene moiety was observed. Since norbornene molecules exist as a mixture of their exo and endo isomers, their identity has been confirmed using two-dimensional (2D)-NMR spectroscopy. Identification of the endo isomer begins with the assignment of its olefinic protons, H6 and H5. These protons revealed strong coupling with each other and were assigned to the resonance in the range of 5.89-5.91 and 6.01-6.06 ppm for H6 and H5, respectively. The bridgehead protons, H1 and H4, were then recognized based on their correlations with the olefinic protons. H1 appeared between 3.39-3.49 ppm & 3.51-3.56 ppm for monomers 7 and 8, respectively. Whereas H4 was found slightly upfield at 2.83-2.95 ppm for monomer 7 and at 2.84 for monomer 8. The exclusive coupling of H1 and H2 in the endo isomer indicated that the broad singlet at 2.14 and 2.15 ppm is corresponding to H2n of monomer 7 and 8, respectively. This assignment was verified based on the connectivity of the H2 resonance, with two peaks appearing further upfield in the spectrum in the range of 0.36-0.54 and 1.1.66-1.1.83 ppm, which represent the H3x and the H3n, respectively. The bridge protons, H7a and The structural identity of the new monomeric units was accomplished using NMR spectroscopic analysis. For example, the carboxylic resonance at 12.38 ppm of spiropyran 4 disappeared from the corresponding monomer 7 due to the formation of the ester link. Also, the methylene protons of compound 5 was shifted further upfield upon esterification. Meanwhile, the presence of the new resonances of the norbornene moiety was observed. Since norbornene molecules exist as a mixture of their exo and endo isomers, their identity has been confirmed using two-dimensional (2D)-NMR spectroscopy. Identification of the endo isomer begins with the assignment of its olefinic protons, H 6 and H 5 . These protons revealed strong coupling with each other and were assigned to the resonance in  1 and H 2 in the endo isomer indicated that the broad singlet at 2.14 and 2.15 ppm is corresponding to H 2 n of monomer 7 and 8, respectively. This assignment was verified based on the connectivity of the H 2 resonance, with two peaks appearing further upfield in the spectrum in the range of 0.36-0.54 and 1.1.66-1.1.83 ppm, which represent the H 3x and the H 3n , respectively. The bridge protons, H 7a and H 7s , also exhibited strong coupling with each other and resonated as multiplets between 1.11-1.44 ppm (H 7a ) and 1.66-1.83 ppm (H 7s ).
The exo isomeric protons were identified using a similar stepwise strategy. The olefinic protons H 6 and H 5 appeared within the multiplet between 5.96-5.97 and 6.01-6.16 ppm for both isomers, while their characteristic couplings with the two bridgehead protons were then used to assign H 1 to the multiplet in the range of 3.26-3.30 ppm and H 4 to the broad singlet appearing between 3.10 and 3.16 ppm. In contrast to the endo isomer, H 2 in the exo isomer does not have any connectivity with H 1 [77,78] , while the determination of this proton was based on its coupling with the two H 3 protons, it was assigned to the multiplet between 1.66 and 1.83 ppm. H 3x (m, δ 1.11-1.44 ppm) was identified via its coupling with the bridgehead proton H 4 , however this coupling could not be observed with H 3n [77,78]. Finally, both H 7 protons were assigned to the multiplet between 1.11 and 1.44 ppm.

ROMP and Thermal Analysis
Polymerization of the new monomeric units, 7 and 8, was achieved via ring opening metathesis polymerization (ROMP) using Grubbs' catalyst. The reactions were performed using monomer/initiator ratio 100/1 over a period of 2 h. The resulting polymers precipitated from the dichloromethane solution during this time, and the reactions were terminated on the addition of ethyl vinyl ether, Scheme 3. H7s, also exhibited strong coupling with each other and resonated as multiplets between 1.11-1.44 ppm (H7a) and 1.66-1.83 ppm (H7s).
The exo isomeric protons were identified using a similar stepwise strategy. The olefinic protons H6 and H5 appeared within the multiplet between 5.96-5.97 and 6.01-6.16 ppm for both isomers, while their characteristic couplings with the two bridgehead protons were then used to assign H1 to the multiplet in the range of 3.26-3.30 ppm and H4 to the broad singlet appearing between 3.10 and 3.16 ppm. In contrast to the endo isomer, H2 in the exo isomer does not have any connectivity with H1 [77,78], while the determination of this proton was based on its coupling with the two H3 protons, it was assigned to the multiplet between 1.66 and 1.83 ppm. H3x (m, δ 1.11-1.44 ppm) was identified via its coupling with the bridgehead proton H4, however this coupling could not be observed with H3n [77,78]. Finally, both H7 protons were assigned to the multiplet between 1.11 and 1.44 ppm.

ROMP and Thermal Analysis
Polymerization of the new monomeric units, 7 and 8, was achieved via ring opening metathesis polymerization (ROMP) using Grubbs' catalyst. The reactions were performed using monomer/initiator ratio 100/1 over a period of 2 h. The resulting polymers precipitated from the dichloromethane solution during this time, and the reactions were terminated on the addition of ethyl vinyl ether, Scheme 3. The new polymers were isolated as plastic sheets, which were completely insoluble in common organic solvents such as chloroform, dichloromethane, acetone, dimethylformamide, and dimethyl sulfoxide. The insolubility of these materials could be attributed to their high molecular weights along with the use of the low ratio of the initiator. The thermal behavior of the desired polymeric materials was performed using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TGA thermograms of polymers 9 and 10 revealed two distinctive weight The new polymers were isolated as plastic sheets, which were completely insoluble in common organic solvents such as chloroform, dichloromethane, acetone, dimethylformamide, and dimethyl sulfoxide. The insolubility of these materials could be attributed to their high molecular weights along with the use of the low ratio of the initiator. The thermal behavior of the desired polymeric materials was performed using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TGA thermograms of polymers 9 and 10 revealed two distinctive weight losses. The first weight loss is between 400 and 447 • C, and is attributed to the partial decomposition of the pendent spiropyran motifs with degradation of the polymer backbone, while the second weight loss is between 530 and 600 • C and is corresponding to the degradation of the remaining polymeric chains.
The glass transition temperature of the new polymers was investigated using DSC measurements. It is well known that polynorbornene is a rather flexible chain, arising from its low T g value [79,80]. This value can be manipulated via incorporation of different molecules into the side chain of the polymers [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. Therefore, it is anticipated that the functionalization of norbornene monomers with the spiropyran moieties increases the T g values of their corresponding polymers. The DSC thermograms of polymers 9 and 10 exhibits a T g value of 136 • C and 127 • C, respectively. Figure 1 is representative examples of TGA, DSC thermograms, and FT-IR analysis. of the pendent spiropyran motifs with degradation of the polymer backbone, while the second weight loss is between 530 and 600 °C and is corresponding to the degradation of the remaining polymeric chains.

Thermochromic Behavior
The prepared polymers displayed a reversible thermochromic behavior upon being exposed to heat either as a dry or wet solid sheet. The wettability was tested against humidity and in various organic solvents, such as dichloromethane, dimethyl formamide, methanol, and chloroform. Unlike some thermochromic systems [81], the new polymers displayed excellent thermochromic performance either as a dry or wet sheet. In general, this behavior corresponds to the transition process of the spiroheterocyclic moiety in the polymer side chain to the quasi-planar open merocyanine. The colored merocyanine form has been known for its strong tendency to associate into aggregates with a stack-like arrangement of the merocyanine molecules [82]. This behavior is triggered by the high concentration of the spiropyran molecules and manipulates their optical response [83,84]. The molecular dipole arrangement of the merocyanine usually takes place in two different styles, H-aggregates that are responsible for the production of the hypthochromic shift in the absorption band, while the J-aggregates produces the bathochromic shift in the absorption band [83,84].

Thermochromic Behavior
The prepared polymers displayed a reversible thermochromic behavior upon being exposed to heat either as a dry or wet solid sheet. The wettability was tested against humidity and in various organic solvents, such as dichloromethane, dimethyl formamide, methanol, and chloroform. Unlike some thermochromic systems [81], the new polymers displayed excellent thermochromic performance either as a dry or wet sheet. In general, this behavior corresponds to the transition process of the spiroheterocyclic moiety in the polymer side chain to the quasi-planar open merocyanine. The colored merocyanine form has been known for its strong tendency to associate into aggregates with a stack-like arrangement of the merocyanine molecules [82]. This behavior is triggered by the high concentration of the spiropyran molecules and manipulates their optical response [83,84]. The molecular dipole arrangement of the merocyanine usually takes place in two different styles, H-aggregates that are responsible for the production of the hypthochromic shift in the absorption band, while the J-aggregates produces the bathochromic shift in the absorption band [83,84]. Figure 2 illustrates the influence of temperature on the polymer optical response. Upon exposure to heat, the color of the polymeric materials changed from reddish orange color into dark gray. This color range is attributed to the conformation of the spiropyran into the zwitrionic merocyanine form that is associated with bathochromic shift due to the presence of the J-aggregates.
Polymers 2017, 9, 630 9 of 16 Figure 2 illustrates the influence of temperature on the polymer optical response. Upon exposure to heat, the color of the polymeric materials changed from reddish orange color into dark gray. This color range is attributed to the conformation of the spiropyran into the zwitrionic merocyanine form that is associated with bathochromic shift due to the presence of the J-aggregates.

Plasma Treatment and X-Ray Diffraction
The surface properties of polymers are utilized for their possible applications, however these properties in most cases do not meet the required purposes. Tailoring the surface properties of the polymeric materials has been the focus of many studies [72][73][74][75]. One of the successful techniques that has been used to achieve this goal is the plasma treatment, which provides morphological changes to these materials [72][73][74][75]. Properties such as scratch-resistance, wettability, biocompatibility, gas transmission, adhesion, and friction could be optimized using different types of plasma systems, and afford great opportunities to suit the desired applications [72][73][74][75]. For example, Neves' group reported the treatment of electrospun polycaprolactone nanofiber meshes (NFMs) by radiofrequency (RF) plasma containing (Ar or O2). This technique allowed for the improvement of the surface hydrophilicity through forming oxygen containing groups at the surface of the polymer, which enhanced their biological performance, such as adhesion and proliferation over three model cell lines, fibroblasts, chondrocytes, and osteoblasts [73].
In this study, the surface of the new polymers was examined using scanning electron microscope (SEM) in order to study its morphology. As anticipated, polynorbornene containing spiropyran molecules are distinguished by their highly porous and amorphous surface, as seen in Figure 3. Modification of the surface character has been achieved using atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma treatment at different periods of time; the surface has been exposed to the plasma system for two, five, and ten minutes. The interaction with the surface was carried out using sinusoidal waveform signal of 23 kV and 25 kHz and its effect on the surface characteristic has been monitored via SEM images. As can be seen in Figures 4 and 5, the porosity of the polymers has been reduced upon the plasma treatment. Moreover, with increasing the time period of the treatment, some surface areas have been changed to be completely nonporous. Other regions exhibited highly ordered thread-like structures that could be attributed to the J-aggregates of the merocyanine form [85]. These surface changes could broaden the applications of this class of materials into areas such as non-porous membranes for reverse osmosis, nanofiltration, or molecular separation in the gas phase.

Plasma Treatment and X-ray Diffraction
The surface properties of polymers are utilized for their possible applications, however these properties in most cases do not meet the required purposes. Tailoring the surface properties of the polymeric materials has been the focus of many studies [72][73][74][75]. One of the successful techniques that has been used to achieve this goal is the plasma treatment, which provides morphological changes to these materials [72][73][74][75]. Properties such as scratch-resistance, wettability, biocompatibility, gas transmission, adhesion, and friction could be optimized using different types of plasma systems, and afford great opportunities to suit the desired applications [72][73][74][75]. For example, Neves' group reported the treatment of electrospun polycaprolactone nanofiber meshes (NFMs) by radio-frequency (RF) plasma containing (Ar or O 2 ). This technique allowed for the improvement of the surface hydrophilicity through forming oxygen containing groups at the surface of the polymer, which enhanced their biological performance, such as adhesion and proliferation over three model cell lines, fibroblasts, chondrocytes, and osteoblasts [73].
In this study, the surface of the new polymers was examined using scanning electron microscope (SEM) in order to study its morphology. As anticipated, polynorbornene containing spiropyran molecules are distinguished by their highly porous and amorphous surface, as seen in Figure 3. Modification of the surface character has been achieved using atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma treatment at different periods of time; the surface has been exposed to the plasma system for two, five, and ten minutes. The interaction with the surface was carried out using sinusoidal waveform signal of 23 kV and 25 kHz and its effect on the surface characteristic has been monitored via SEM images. As can be seen in Figures 4 and 5, the porosity of the polymers has been reduced upon the plasma treatment. Moreover, with increasing the time period of the treatment, some surface areas have been changed to be completely nonporous. Other regions exhibited highly ordered thread-like structures that could be attributed to the J-aggregates of the merocyanine form [85].
These surface changes could broaden the applications of this class of materials into areas such as non-porous membranes for reverse osmosis, nanofiltration, or molecular separation in the gas phase.   The X-ray diffraction of spiropyran containing polynorbornenes confirms the amorphous nature of the polymer, as seen in Figure 6a [86]. Moreover, the presence of the broad halo refers to the low stereoregularity of the polymer segments. The pattern shows a number of Bragg reflections, which can be indexed on the bases of the face centered cubic (FCC) structure of ruthenium. The diffraction   The X-ray diffraction of spiropyran containing polynorbornenes confirms the amorphous nature of the polymer, as seen in Figure 6a [86]. Moreover, the presence of the broad halo refers to the low stereoregularity of the polymer segments. The pattern shows a number of Bragg reflections, which can be indexed on the bases of the face centered cubic (FCC) structure of ruthenium. The diffraction   The X-ray diffraction of spiropyran containing polynorbornenes confirms the amorphous nature of the polymer, as seen in Figure 6a [86]. Moreover, the presence of the broad halo refers to the low stereoregularity of the polymer segments. The pattern shows a number of Bragg reflections, which can be indexed on the bases of the face centered cubic (FCC) structure of ruthenium. The diffraction The X-ray diffraction of spiropyran containing polynorbornenes confirms the amorphous nature of the polymer, as seen in Figure 6a [86]. Moreover, the presence of the broad halo refers to the low stereoregularity of the polymer segments. The pattern shows a number of Bragg reflections, which can be indexed on the bases of the face centered cubic (FCC) structure of ruthenium. The diffraction peaks obtained at 2θ = 38.6, 44, 64.5, and 77.6 are identical with those reported for the standard ruthenium metal, which indicates the presence of some traces of ruthenium catalyst that have been trapped in the polymer matrix. Meanwhile, the interlayer spacing of polymer 9 (Figure 6a) can be calculated using the defined peak at 2θ = 18.5 • that is according to Bragg's equation (with λ = 1.54 Å) and corresponds to d = 7.9 Å. Figure 6b illustrates the diffraction patterns of polymer 9 after being exposed to the atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma. As we mentioned previously, the treatment of the polymer surface with the DBD system has been tested at different periods of time. XRD comparison between the untreated sample and the treated ones (Figure 6c) showed that the width of the broad halo decreases with the increase of the treatment time. This could be attributed to the highly ordered J-aggregates of the merocyanine form in thread like-structures as a result of DBD plasma operating sinusoidal high voltage [85]. This hypothesis is also supported by the SEM images, Figure 5. It is also important to mention that the broad halo peaks for the treated polymers were not shifted to higher 2θ values, which means that the structures of these polymers did not change after the plasma treatment. peaks obtained at 2θ = 38.6, 44, 64.5, and 77.6′′ are identical with those reported for the standard ruthenium metal, which indicates the presence of some traces of ruthenium catalyst that have been trapped in the polymer matrix. Meanwhile, the interlayer spacing of polymer 9 (Figure 6a) can be calculated using the defined peak at 2Ɵ = 18.5° that is according to Bragg's equation (with λ = 1.54 Å ) and corresponds to d= 7.9 Å . Figure 6b illustrates the diffraction patterns of polymer 9 after being exposed to the atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma. As we mentioned previously, the treatment of the polymer surface with the DBD system has been tested at different periods of time. XRD comparison between the untreated sample and the treated ones (Figure 6c) showed that the width of the broad halo decreases with the increase of the treatment time. This could be attributed to the highly ordered J-aggregates of the merocyanine form in thread like-structures as a result of DBD plasma operating sinusoidal high voltage [85]. This hypothesis is also supported by the SEM images, Figure  5. It is also important to mention that the broad halo peaks for the treated polymers were not shifted to higher 2θ values, which means that the structures of these polymers did not change after the plasma treatment.

Conclusions
Chromogenic polymers hold a special place due to their potential applications in various fields, such as optical devices, data storage, and switches. This research work illustrates a successful attempt to functionalize norbornene monomers with spiropyran moieties to tailor the properties of their corresponding polymer. Successful ring opening metathesis polymerization of the new monomers allowed for the isolation of polynorbernene pendent spiropyran moieties. The new polymers displayed reversible thermochromic ability due to the conversion of the closed spiropyran moiety to the open merocyanine form that is associated with bathochromic shift due to the presence of the Jaggregates. In the meantime, the obtained polymers exhibited an amorphous nature with a high porosity. This texture enhances the thermochromic ability of the polymers due to the presence of the leuco dyes, as well as their nematic nature. Treatment of the obtained polymers with atmospheric

Conclusions
Chromogenic polymers hold a special place due to their potential applications in various fields, such as optical devices, data storage, and switches. This research work illustrates a successful attempt to functionalize norbornene monomers with spiropyran moieties to tailor the properties of their corresponding polymer. Successful ring opening metathesis polymerization of the new monomers allowed for the isolation of polynorbernene pendent spiropyran moieties. The new polymers displayed reversible thermochromic ability due to the conversion of the closed spiropyran moiety to the open merocyanine form that is associated with bathochromic shift due to the presence of the J-aggregates. In the meantime, the obtained polymers exhibited an amorphous nature with a high porosity. This texture enhances the thermochromic ability of the polymers due to the presence of the leuco dyes, as well as their nematic nature. Treatment of the obtained polymers with atmospheric pressure air Dielectric Barrier Discharge (DBD) plasma changes the porosity of the surface, which make this class of polymer eligible for various applications, such as non-porous membranes for reverse osmosis, nanofiltration, or molecular separation in the gas phase.