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Polymer 55 (2014) 2362e2368

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Polymer

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Photo-induced aminobenzoate group formation on a polymericphotobase generator bearing N-phenylcarbamate groups and itsapplication to color imaging material

Kyu Ho Chae*, U Chan Yang, Min Kwon LeeDepartment of Polymer Engineering, Chonnam National University, Gwangju 500-757, Republic of Korea

a r t i c l e i n f o

Article history:Received 20 January 2014Received in revised form17 March 2014Accepted 21 March 2014Available online 27 March 2014

Keywords:ImagingPhotobase generatorPhoto-Fries rearrangement

* Corresponding author. Tel.: þ82 62 530 1874; faxE-mail address: khochae@chonnam.ac.kr (K.H. Cha

http://dx.doi.org/10.1016/j.polymer.2014.03.0370032-3861/� 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

A polymeric photobase generator bearing N-phenylcarbamate groups was prepared to generate aromaticamino groups upon irradiation and used for color imaging on a thin polymer film. Polymer bearing N-phenylcarbamate groups was prepared by copolymerization of methacryloyloxyethyl phenylcarbamate(MPC) and methyl methacrylate (MMA). The photochemical process of the polymer was monitoredthrough the UV and IR absorption spectral analyses and contact angle measurements. Irradiation of thepolymer led to the formation of aminobenzoate groups through the photo-Fries type rearrangement orcross-linking through the radical coupling reaction of N-phenylcarbamate groups. The cosinus values ofcontact angle (q) of the polymer film decreased upon irradiation indicating that the polymer surfacedeveloped a hydrophobic property. A color image was produced by a diazocoupling reaction of theaminobenzoate groups which were produced in the irradiated area of the polymer film with phenolic oraromatic amino coupling agent. The yellow color was developed by resorcinol or aniline treatment,whereas the red color was produced by the naphthol AS or 1-naphthylamine treatment.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Photobase generators (PBGs) are a group of compounds that,upon irradiation, produce a base. PBGs have attracted great atten-tion, due to their possible applicability to the development of newtechnologies. They have been used as photochemical cross-linkingagents for epoxy resins, and also as photoresists, surface modifiers,and imidation catalysts, etc. In the last decade, photobase genera-tors have expended their application to new fields [1]. For example,they have been used for the preparation of photosensitive poly-imides [2,3], polybenzoxazole [4], and as a catalyst for photo-induced depolymerization [5,6] and living anionic ring-openingpolymerization [7], nanoparticle assemble on substrate [8], fabri-cation of a deposited silver micropattern [9], and so on. New ap-plications of photobase generators as imaging materials have alsobeen reported such as fluorescence patterning [10,11], color imag-ing [12,13], and imaging of proteins or biomolecules [14,15].

A variety of chemical systems, such as o-nitrobenzoyl carba-mates and urethanes, ammonium salts, amine complex, o-

: þ82 62 530 1909.e).

acyloximes, formamides, and oxime-urethanes have been reportedto photochemically produce free amines. Recently, new classes ofPBGs have been examined, including ammonium salts, aminei-mides, a-aminoketone, benzyl substituted amidine, and aromaticurea. Some studies on PBGs have focused on improvements in theirthermal stability, photosensitivity, multi-functionality, and onsensitization to longer wavelength light [1].

Aromatic photobase generation has been reported from thepolymer bearing anilide groups through rearrangement. Photo-anilide rearrangement is an acylanilide photochemical process toproduce aminoketone upon irradiation [16]. The reaction has beenapplied to prepare polyfunctional amines for thermal curing re-actions of epoxy resin and polyurethane oligomers [17,18]. Poly-mers containing N-phenylamide groups have been used tomodulate the refractive index and to obtain functionalized andpatterned surfaces [19]. Polymers bearing anilide groups have beenapplied to form fluorescent micropatterns [20].

Various kinds of photo-removable carbamates have been re-ported as the protecting groups for amines [21]. In these cases,photobase was generated from the photolytic cleavage of thecarbamate group. However, aminobenzoate group formation fromthe polymer bearing carbamate groups has not been observedthrough the photo-Fries type rearrangement. Since the aromatic

Table 1Polymerization conditions and physical properties of polymer.

Polymera Monomer Monomer unit in feed Monomer unit foundb Yield (%) Mnc Mw=Mn

MPC (g) MMA (g) DMF (ml) AIBN (mg) MPC (mol%) MMA (mol%) MPC (mol%) MMA (mol%)

I 0.25 0.1 2 1.75 50 50 51 49 65 59100 2.15II 0.25 e 2 1.25 100 e 100 e 63 12100 1.95

a Polymerization was carried out in DMF at 70 �C for 20 h.b Determined from 300 MHz NMR spectra.c Measured by GPC in CHCl3 at 25 �C.

K.H. Chae et al. / Polymer 55 (2014) 2362e2368 2363

amino groups can be a useful functionality for their application tovarious polymer systems, and to develop polymeric photobasegenerator bearing various functional groups for their wider appli-cations, the photochemical process of the polymeric photobasegenerator bearing N-phenylcarbamate groups was studied. How-ever, little attention has been focused on the photobase generationfrom N-arylcarbamate via the photo-Fries type rearrangement. Itwas reported that irradiation of ethyl N-phenylcarbamate led to theformation of ethyl o-aminobenzoate, ethyl p-aminobenzoate, andaniline; and the yield of the products is concentration dependent[22,23].

In previous studies, carbamoyloximes (oxime-urethanes) [24]and phthalimido carbamates [11,25] have been proposed as newPBGs. A polymeric photobase generator containing carbamoylox-ime groups can be used for fluorescent patterning [10], and colorimaging on a thin polymer film [12,13]. A polymer containingphthalimido carbamate groups was used as a bicolor fluorescentpatterning material [11]. As a continuing study to develop a poly-meric photobase generator based on carbamates, herein we reportaminobenzoate group formation from the polymer bearing N-phenylcarbamate groups through the photo-Fries type rearrange-ment reaction, which was applied to form a color image. A multi-step process is needed to prepare photo-removable aromaticamino group [12]. However, the steps can be greatly reduced,through the change of the photoreaction from cleavage (photo-protection) to rearrangement (photo-Fries type) reaction, to pro-duce aromatic amino groups. The photo-Fries type rearrangementreaction of polymer bearing N-arylcarbamate groups offers anothereasy and simple way to produce aromatic photobase.

2. Experimental

2.1. Materials and instruments

Phenyl isocyanate was obtained from Aldrich Chemicals Co. 2-Hydroxyethyl methacrylate (HEMA) and methyl methacrylate(MMA) were purchased from Fluka and Junsei Chemicals Co.,respectively. MMA was purified by alumina column chromatog-raphy, to remove the polymerization inhibitor. Resorcinol, naphtholAS, and 1-naphthylamine were obtained from TCI Chemicals Co.Methacryloyloxyethyl phenylcarbamate (MPC), a monomer con-taining phenylcarbamate group, was prepared by a reaction withHEMA and phenyl isocyanate using a procedure previously re-ported [26]. Ultraviolet (UV) absorption spectrawere obtained witha Jasco V-530 spectrophotometer. Infrared (IR) absorption spectrawere taken on a Shimadzu model FTIR-8300. 1H nuclear magneticresonance spectra were obtained on a Bruker ASX-32 300 MHzspectrometer. Contact angle was measured with a Surface Techmodel GSA contact-angle meter. Gel permeation chromatography(GPC) was carried out, using a Viscotek model GPC Mzs & TetraDetector Array. A PL gel model mixed-B LS columnwas used for themolecular weight determination measurements, using polystyrenestandards. Chloroform was used as the eluent at a flow rate of

1.0 mL/min. Column temperature was maintained at 40 �C. Onemodule of a Rayonet photochemical reactor (Southern New En-gland UV Co., model RPR-208), which was equipped with a 254 nmfluorescent lamp, was horizontally placed and used to irradiate thepolymer films. A light intensity of 3.54 mW/cm2 at 254 nm wasmeasured using a radiometer (Vilber Lourmat Co., model VLX-3W).

2.2. Polymerization

The reaction conditions used to prepare polymers are shown inTable 1. The typical polymerization conditions for preparing poly-mer I are shown below. MMA (0.1 g, 1.0 mmol), MPC (0.25 g,1.0 mmol), and azobisisobutyronitrile (AIBN) (1.75 mg, 0.5 wt% ofmonomers) were dissolved in dimethylformamide (DMF) (2.0 mL).The DMF solution was charged into a cap tube, and purged withnitrogen for 15 min. After the cap tube containing the reactionmixture was sealed, polymerization was carried out at 70 �C for20 h. The polymer was isolated by double precipitation from theDMF solution into methanol and dried under reduced pressure at50 �C for 3 h. The yield was 65% (0.23 g).

Polymer I: IR (KBr pellet, cm�1): 3361, 2989, 2950, 1733, 1596,1541, 1446, 1217, 1153, 758, 690. Polymer II: IR (KBr pellet, cm�1):3346, 2958, 1726, 1600, 1541, 1446, 1313, 1220, 758, 690.

2.3. Film preparation

A 5.0 wt% polymer solution was prepared, by dissolving 0.2 gpolymer in THF (4mL). The polymer solutionwas spin coated onto aquartz plate, a glass plate, or a silicon wafer pre-treated with H2O2and H2SO4, to form an oxide layer [27] consecutively at 2000 rpmfor 10 s, and 4000 rpm for 10 s. The polymer film on the quartz plateor silicon wafer was dried at 100 �C for 20 min. The film measuringIR absorption spectra was obtained, after coating the 5.0 wt%polymer solution in THF onto the KBr pellet, using a solvent castingmethod. The casted polymer filmwas dried under reduced pressureat 50 �C for 3 h.

2.4. Measurement of contact angle

Distilled water (20 mL) was dropped onto the surface of thepolymer film on a glass plate, and after 30 s, the contact angle wasmeasured. The contact angle was measured at five different sites oneach specimen, and the mean value was calculated. To observe theeffect of HCl treatment on the contact angle, the irradiated polymerfilm on the glass plate was dipped in 1 NHCl for 1min, washedwithdistilled water for 30 s, and then dried at 50 �C for 1 h, underreduced pressure. The contact angle of the film was measured bythe same procedure detailed above.

Three sets of five polymer I films were prepared on the glassplate, to test the reproducibility of the contact anglemeasurements.One set of the five polymer films was used to measure the contactangle of the non-irradiated polymer films. The contact angle wasmeasured of another set of the five polymer films, which were

Wavelength (nm)

Abs

orba

nce

1.5

1.0

0.5

0200 250 300 350 400

10 (J/cm2)86420

Fig. 1. UV absorption spectral changes of a polymer I film on the quartz plate uponirradiation with 254 nm UV light over 0, 2, 4, 6, 8, and 10.0 J/cm2.

K.H. Chae et al. / Polymer 55 (2014) 2362e23682364

irradiated with 4.0 J/cm2 of 254 nm UV light, and that of the otherset of the five films, which were treated with 1 N HCl. For thereproducibility measurements,10 mL of distilled water was droppedon the polymer surface and the contact angle was measured within15 s.

2.5. Diazocoupling reaction

2.5.1. UVevis absorption spectraPolymer II film on a quartz plate or glass plate was irradiated

with 10.0 J/cm2 of 254 nmUV light. The irradiated polymer filmwasimmersed in a diazo solution (0.3 g NaNO2 and 1.0 mL concentratedHCl in 4 mL THF and 16mL H2O) for 6 min at 5 �C, and subsequentlydipped in a coupling agent solution for 2 min. Resorcinol couplingsolution was prepared by dissolving resorcinol (0.4 g) in 4 mL THFand 16 mL H2O. Naphthol-AS (0.02 g), aniline (0.56 mL), and 1-naphthylamine (0.44 g) coupling solutions were prepared by us-ing the same procedure. The film was washed in 4 mL THF and16 mL H2O and then dried at 50 �C for 3 h under reduced pressure.The UVevis absorption spectrum of the dried film on the quartzplate was observed.

2.5.2. Color image formationPolymer II film on a glass plate was covered with a photomask,

and irradiated with 254 nm UV light (10.0 J/cm2). The irradiatedfilm on the glass plate was first dipped in a diazo solution for 6 minat 5 �C and subsequently dipped in a coupling agent solution for2 min. The film was then washed in 4 mL THF and 16 mL H2O anddried at 50 �C for 3 h under reduced pressure. The color imageformed on the polymer film was observed with a Canon DSLR 400camera.

3. Results and discussion

3.1. Polymerization and photochemical reaction

Polymer I bearing N-phenylcarbamate groups was prepared bycopolymerization of MPC and MMA, and polymer II was preparedby homopolymerization of MPC. Table 1 shows the polymerizationconditions and physical properties of the polymers. The number ofMPC units incorporated into the polymer was similar to that in thefeed. The molecular weight of the copolymer (polymer I) washigher than that of the homopolymer (polymer II), which seemedto be due to the steric effect of the phenylcarbamate groups. Thepolydispersity of the polymers was 2.15 for polymer I, and 1.95 forpolymer II. The thickness of the film measured by using a scanningelectron microscope was 0.42 mm.

The photochemical reaction of the polymer bearing N-phenyl-carbamate groups was monitored, by observing the UV and IR ab-sorption spectral changes and contact angle measurements. Fig. 1shows the UV absorption spectral changes of a polymer I filmlight on a quartz plate, upon irradiation with 254 nm UV light. Anisosbestic point was observed at around 248 nm. Upon irradiation,absorbance at 220e250 nm decreased and that around 250e350 nm increased. This occurred because irradiation of the polymerbearing N-phenylcarbamate groups resulted in the formation ofaminobenzoate groups, via photolytic cleavage of the CeN bond toform anilinyl radical and carboxyl radical, followed by rearrange-ment or photodegradation.

Fig. 2 illustrates the difference spectrum for a polymer II film onthe KBr pellet, by comparing the absorption spectra before andafter irradiation with 10 J/cm2 of 254 nm UV light. The absorptionbands at 3388 and 3328 cm�1 increased upon irradiation, indi-cating the formation of primary aromatic amino groups. The ab-sorption bands at 2981 and 2869 cm�1 decreased upon irradiation,

indicating the removal of alkyl groups. The decrease in absorptionband at 1733 cm�1 indicates decomposition of the carbamatecarbonyl groups, and the increase in the absorption bands at1693 cm�1 indicates the formation of benzoate carbonyl groups.The decrease in the absorption band at 1085 cm�1 indicates thedecomposition of carbamate CeN groups. The degree of rear-rangement from N-phenylcaramate to aminobenzoate groups inthe polymer II was about 10%, which was measured by the decreasein absorbance at 1085 cm�1.

Masilamani et al. [23] reported that irradiation of ethyl N-phe-nylcarbamate leads to the formation of ethyl o-aminobenzoate,ethyl p-aminobenzoate, aniline, CO2, CO, and ethylene through thephoto-anilide type rearrangement. Similarly, it was very likely thatirradiation of the polymer film led to the photolytic cleavage ofcarbamate CeN bonds, to form the anilinyl radical and polymerradical pair. The radical pair undergoes photo-induced rearrange-ment to form aminobenzoate; whereas, a polymer radical canfurther photodecompose, to form polymer alkyl or carboxyl radi-cals, after producing CO2 or CH2]CH2, as shown in Scheme 1. Thephotodecomposed polymer radicals undergo radical coupling toform cross-links [28]. Actually, we found that the irradiated poly-mer I film was insoluble in THF.

Changes in surface properties of the polymer film upon irradi-ation were studied with contact angle measurements. Fig. 3 dis-plays the changes in cos q of water on the polymer I film, as afunction of irradiation doses. Unexpectedly, the cosinus value ofcontact angle of the polymer film decreased upon irradiation,indicating that the polymer surface developed a hydrophobicproperty, which seemed to be due to the formation of apolar groupsproduced by the radical coupling reaction of the polymer alkylradicals or polymer carboxyl radical in Scheme 1. It is likely that thehydrophobic properties of the less polar groups, produced by theradical coupling reaction of the polymer radicals, overwhelmed thehydrophilic properties of the aminobenzoate groups, produced bythe photo-Fries type rearrangement. This speculation is supportedfrom the difference IR spectrum in Fig. 2, by the strong negativebands at 2981 and 2869 cm�1.

Wavenumber ( cm-1)4000 3500 3000 2500 15002000 1000 500

-0.04

-0.02

0.00

0.02

0.04

(-)(+

)ΔA

3328

2869

1693

2981

10641733

3388

N-H C=O

C-N

Fig. 2. A difference IR absorption spectrum of a polymer II film on the KBr pellet comparing absorption spectra before and after irradiation with 254 nm UV light for 10.0 J/cm2.

K.H. Chae et al. / Polymer 55 (2014) 2362e2368 2365

Treatment of the irradiated polymer film with HCl resulted in aslight increase in cos q value, but the cos q value was still less thanbefore irradiation. The result indicates that the polymer surfacechanged to become somewhat hydrophilic by treatment with HCl,due to the formation of ammonium salts from the rearrangedaminobenzoate groups. However, the surface is still more hydro-phobic than before irradiation, notwithstanding the HCl treatment.This is due to the apolar groups, which formed on the polymersurface through the photochemical reaction of N-phenylcarbamategroups. The contact angle of the irradiated and HCl treated polymerfilm cannot be restored to its original value, since the chemicalstructure of the polymer surface had already changed by thephotochemical transformation to more apolar functional groups.

Three sets of the five polymer I films (non-irradiated, irradiatedwith 4.0 J/cm2, and non-irradiated polymer film after the HCltreatment) were prepared, to test the reproducibility of the contactangle measurements, and to confirm the changes of the contactangle at different reaction conditions. The average value of the

CH3

CCH2 C

CH3

CC OOCH2

CH2OCNH

O

OO

CH3 hv

CH2

CH3

CCH2

C OOCH2

CH2OC O

NH2

HCl

x y

rearra

ngem

ent

Scheme 1. A possible photochemical process of a polymeric photobase generat

contact angle of the non-irradiated polymer film was 66.6, withstandard deviation (s) of 0.37; and that of the irradiated film was70.1, with s ¼ 0.75. The contact angle of non-irradiated polymerfilm after the HCl treatment was 67.9 (s¼ 0.69). The result indicatesthat no appreciable change of the contact angle was observed be-tween non-irradiated (q ¼ 66.6), and non-irradiated polymer filmafter the HCl treatment (q¼ 67.9). However, somewhat higher valuewas observed in the case of the irradiated polymer film (q¼ 70.1). Itcan be confirmed that the surface of the polymer film changed tomore hydrophobic property by the photo-irradiation.

3.2. Color imaging

The polymeric photobase generator bearing N-phenylcarbamategroups was applied to produce a color image through the diazo-coupling reaction. Scheme 2 shows a series of chemical reactions,through which the irradiated copolymer can function as a colorimaging material. Irradiation of the copolymer bearing N-

CH3

CCH2

C OOCH2

CH2OC O

NH+3Cl

CH3

CCH2

C OOCH2

CH2OC

NH

O

cross-linking

CO2

CH3

C

C OOCH2

CH2

CH2

CH2

radicalcoupling

CH4

+ aniline

or bearing N-phenylcarbamate groups, and subsequent reaction with HCl.

0 1 2 3 4

0.40

0.45

0.50

0.55

Irradiation intensity (J/cm2)

Cos

θ

Fig. 3. The cosinus value of the contact angle of water on the polymer I film uponirradiation with 254 nm UV light (C) followed by treatment with HCl (B).

CH3

CCH2 C

CH3

CC OOCH2

CH2

OC

NH

O

OO

CH3

hvCH2

CH3

C CH2C

CH3

CC OOCH2CH2

OC O

OO

CH3

CH2

RO

OHOH

,CONH

Coupling agen

x y

N2+Cl

_

y

Scheme 2. Chemical reactions for photo-Fries type rearrangement of polymer bearing N-pagents.

K.H. Chae et al. / Polymer 55 (2014) 2362e23682366

phenylcarbamate groups led to the formation of pendant amino-benzoate groups in the irradiated area. Subsequent reaction withsodium nitrite generated diazonium salts. Treatment of thegenerated diazonium salts with phenolic compounds or aromaticamine resulted in the formation of diazo groups on the polymerchain. Various colors can be developed, depending on the couplingreagents employed.

3.2.1. Diazocoupling with a phenolic coupling agentFig. 4 demonstrates the UVevis absorption spectra of the poly-

mer II films on a quartz plate after irradiation with 10.0 J/cm2 of254 nm UV light, followed by treatment with nitrous acid, and asubsequent reaction with resorcinol or naphthol AS. The irradiatedpolymer film showed no absorption �400 nm. However, a yellowcolor developed, and absorbance at about 410 nm increased fromthe reaction with resorcinol (solid line); whereas, a red colordeveloped, and the absorbance at about 520 nm increased from thereaction with naphthol AS (dashed line).

The reactionwasmonitored by UVevis absorption spectroscopy,by varying the reaction temperature and immersion time in thenitrous acid solution, to optimize the reaction conditions for colorimaging. The polymer film on the quartz plate was irradiated with10 J/cm2 of 254 nm UV light, and the irradiated polymer film wasimmersed in a nitrous acid solution at reaction temperature of 5e35 �C. The immersed film was subsequently dipped in naphthol ASsolution for 2 min and the absorbance of the film at 500 nm wasmonitored. When the reaction temperature of the diazonium so-lution increased, the absorbance of the film at 500 nm gradually

CH3

CCH2 C

CH3

CC OOCH2

CH2OC O

OO

CH3

CH2

NH2

H

NaNO2, HCl

t

CH3

C CH2C

CH3

CC OOCH2CH2

OC O

OO

CH3

N N R

CH2

NH2

NH2

,or

y

y

henylcarbamate groups, and subsequent diazocoupling reaction with various coupling

Wavelength (nm)

Abs

orba

nce

1.5

1.0

0.5

0200 300 400 600500

2.0

300 400 500

0.1

600

0.2

0

resorcinolnaphthol-AS

Fig. 4. UVevis absorption spectra of polymer II films on the quartz plate after irradi-ation followed by diazotization and subsequent treatment with resorcinol (dd) ornaphthol AS (- - - -).

Abs

orba

nce

Wavenumber(nm)

2.0

1.0

1.5

0

0.5

200 300 500400 600

0.2

0.1

0400300 500 600

aniline

1-naphthyl amine

Fig. 6. UVevis absorption spectra of polymer II films on the quartz plate after irradi-ation followed by diazocoupling reaction with aniline (ddd) or 1-naphthylamine($$$$$$).

K.H. Chae et al. / Polymer 55 (2014) 2362e2368 2367

decreased. Therefore, the optimum reaction temperature was�5 �C. The optimum dipping time in the nitrous acid solution was6 min for resorcinol, and 4 min for naphthol AS. Polymer II wasmore reactive than polymer I.

A thin polymer film on the glass plate was covered with aphotomask and irradiated with 254 nm UV light. A latent image

Reaction with Naphthol ASReaction with resorcinol

Photomask image

Fig. 5. Color images obtained with a polymer II film on the glass plate. Yellow or redimages were obtained when resorcinol or naphthol AS was used as a coupling agent.(For interpretation of the references to color in this figure legend, the reader is referredto the web version of this article.)

was produced in the irradiated area through the formation ofaminobenzoate groups, by the photo-Fries type rearrangement ofthe N-phenylcarbamate groups in the polymer. A consecutive re-action of the aminobenzoate groups with sodium nitrite led to theformation of diazonium salts. Treatment of the diazonium saltswith resorcinol or naphthol AS resulted in the formation of diazogroups through the diazocoupling reaction, and color developed inthe irradiated area.

Fig. 5 demonstrates an example of color images using thepolymer II film. The images in this figure are Mondrian’s artwork,“Tableau I: Lozenge with four lines and gray”. The yellow color wasproduced by resorcinol treatment; whereas, the red color wasproduced by the naphthol AS treatment.

3.2.2. Diazocoupling with an aromatic amineSimilar to diazocoupling reactionwith phenolic compounds, the

reaction was carried out with aromatic amine as a coupling agent.Fig. 6 shows the UVevis absorption spectra of the polymer II filmson the quartz plate, after irradiation with 10.0 J/cm2 of 254 nm UVlight, followed by diazocoupling reaction with aniline or 1-naphthylamine. The irradiated polymer film showed no absorp-tion �400 nm; but a faint yellow color developed, and the absor-bance at around 400 nm slightly increased, from the reaction withaniline (solid line). A red color developed, and the absorbance ataround 500 nm increased from the reaction with 1-naphthylamine(dotted line).

Fig. 7 displays an example of color images using the polymer IIfilm on the glass plate, through the diazocoupling reaction withaniline or 1-naphthylamine as a diazocoupling agent. The faintyellow color was developed by aniline treatment; whereas, the redcolor was developed by the 1-naphthylamine treatment.

4. Conclusions

A new polymeric photobase generator bearing N-phenyl-carbamate groups was developed, to produce aminobenzoate

Reaction with 1-naphthyl amineReaction with anilinePhotomask image

Fig. 7. Color images obtained with a polymer II film on the glass plate. Faint yellow or red images were obtained when aniline or 1-naphthylamine was used as a coupling agent.(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

K.H. Chae et al. / Polymer 55 (2014) 2362e23682368

groups upon irradiation. The aminobenzoate groups can easily beproduced by the photo-Fries type rearrangement of N-phenyl-carbamate groups in the polymeric photobase generator. The sur-face of the polymer changed to a hydrophobic property, due tophotodecomposition of N-phenylcarbamate groups to form lesspolar groups. A color image can be formed after diazotization,through the reaction of produced aminobenzoate groups, bytreating phenolic coupling agent or aromatic amine. Thus, thepolymeric photobase generator bearingN-phenylcarbamate groupsprovides an easy and simpleway to produce aminobenzoate groupsupon irradiation. The polymer can be used for color imaging ma-terial through the photo-Fries type rearrangement of N-phenyl-carbamate groups, and subsequent diazocoupling reaction of theproduced aminobenzoate groups with a phenolic compound oraromatic amine as a coupling agent. Various colors can be devel-oped, depending on the coupling agent.

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