interaction of a diazoresin with sodium dodecyl sulfate in aqueous solution

Macromol. Rapid Commun. 19,291-294 (1998) 29 1

Interaction of a diazoresin with sodium dodecyl sulfate in aqueous solution

Ha0 Luo, Boxuan Yang, Lei Yang, Weiixiao Cao*

College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

(Received: January 26, 1998; revised: February 16, 1998)

SUMMARY The interaction between a diazoresin and sodium dodecyl sulfate (SDS) in aqueous solution was investigated. It was found that the diazoresin-SDS complex dissolves in water containing excessive SDS. The thermal stability and photo-sensitivity of the diazoresin-SDS complex was also studied. The results show that the complex possesses an increased thermal stability while preserving its high photo-sensitivity. An aqueous composition containing diazoresin and SDS was used directly to prepare a photosensitive coating.

Introduction The complexes formed by a polymer chain or its gel and surfactants have attracted more and more attentions recently due to their peculiar pr~pertiesl-~). One of the reasons is that most of the complexation processes invol- ving surfactant exhibit high self-assembly characteristics'@12).

According to the electronic charge carried on the chain, the polymers usually can be divided into two groups, i. e. neutral polymers and polyelectrolytes. The complexes of surfactants with neutral polymers such as poly(ethy1ene ~x ide ) '~ ) , poly(ethy1ene oxide)-bZock-poly(propy1ene oxide)-block-poly(ethy1ene oxide)3), poly(N-isopropyl- a~rylarnide)'~), poly(viny1 al~ohol) '~), gelatin16), and col- lagen") etc. were studied. It was found that the surfactant molecules bind with the polymer chain in an aggregation form rather than as single molecules. In the case of polyelectrolytes, the attention is mainly focused on anionic polyelectrolytes and cationic surfactants such as poly- (sodium styrenesulfonate)/trimethyloctylammonium bro- mide"), poly(acry1ic acid)/cetyltrimethylammonium bro- mide"), cellulose sulfate/cationic surfactants20) etc.

In comparison with that, investigations of the interaction between cationic polyelectrolytes and anionic surfactants are very limited. The poly(2-trimethylammonio ethyl acrylate chloride)/sodium dodecyl sulfate (SDS) system was studied with light scattering and time- resolved fluorescence techniquelo), confirming that the hydrodynamic radius of the polymer in the complex decreases remarkably due to the interaction of polymer and surfactant. The interaction between SDS and a cationic polyelectrolyte formed from N,N,N',N'-tetramethyl- hexamethylenediamine and hexamethylene dibromide has been studied and shows that the 1/1 (mole ratio) complex' exhibits a supermolecular structure which is destroyed subsequently by the addition of excessive SDS and a water soluble complex is formed").

Recently, a new kind of polyelectrolyte/surfactant complexes containing photolabile diazosulfonate chromo- phores were synthesized and confirmed that under irra- diatiqn of UV light the complexes lose their ionic interac- tions22).

In this article the interaction of diazoresin (DR), a poly- condensation product of diphenylamine-4-diazonium salt and formaldehyde, as cationic polyelectrolyte with SDS is investigated. The behaviour in aqueous solution as well as the thermal stability and the photo-sensitivity of the diazoresin/SDS complex (DR-SDS) will be studied.

Experimental part

Preparation of diazoresin

30 mL of concentrated sulfuric acid was added into a 200 mL three necked bottle, 17.6 g (0.055 mol) of diphenylamine-4-diazonium chloride was added in batches under stir- ring. The HCl formed in the reaction was removed by a water pump attached to one of the necks of the bottle, then 2.0 g (0.067 mol as formaldehyde unit) of paraformaldehyde was added at 0-5 "C and stirred for 4 h at the same temperature. The reaction mixture was then poured into 60 mL of ice water to dissolve the diazoresin and then filtered. 10 g (0.074 mol) of ZnC12 was added into the filtrate to precipitate the diazoresin as 1/2 ZnC12 complex. The precipitate was washed with a ZnC12-saturated solution to remove the remaining acid and then dried at room temperature in the dark; yield 15 g (73%), qsp/c = 0.12 dL * g-' (in water), a, = 2640.

Detection of diazoresin in SDS-containing aqueous solution

The diazoresin dissolved in aqueous solution can be detected spectrophotometrically by measuring the absorbance at 380 nm wavelength characteristic for the -N: group in the

0 1998, Hiithig & Wepf Verlag, Zug CCC 1022- 1336/98/$10.00

292

resin. Therefore, the interaction of diazoresin with SDS can be monitored by determing the absorbance of the solution. The procedure was carried out as follows: The SDS solution (3.0 mmol (864 mg) SDS dissolved in 20 mL water) was added in 15-20 batches into the diazoresin solution (1.0 mmol (381 mg) resin in 20 mL water) under stimng at room temperature. After every addition of SDS solution, the mixture was stirred for more than 5 min, then the absorbance A' of the solution at 380 nm was determined. The corrected absorbance A was calculated from the equation

where VI represents the volume of sample solution before addition of SDS, Vz and A' represent the volume and the absorbance of the sample solution after every addition of SDS.

Photochemical and thermal decomposition of diazoresin in SDS-containing aqueous solution

The photochemical and thermal decomposition of diazoresin in SDS-containing aqueous solution was also monitored by means of UV-VIS spectroscopy. In the case of photochemical decomposition, the sample solution was irradiated with a 80 W medium pressure mercury lamp at a distance of 9 cm. The absorbance of the solution at 380 nm was recorded after every irradiation of 10 s. From the decreasing absorbance the photodecomposition was calculated from the equation:

decomposition in mol-% = (1 - A~hoto/A~hoto) - 100% (2)

where Aihoto and APhoto represent the absorbance determined after an irradiation time 0 and an irradiation time t , respectively.

In the case of thermal decomposition, the sample solution was heated in a thermostat at 70 0.1 "C in the dark for a given time, then the absorbance of the solution was measured spectrophotometrically. From the decreasing absorbance, the thermal decomposition was calculated from the analogous equation

decomposition in mol-% = (1 - A:hemal/Armal) * 100% (3)

where and represent the absorbance of the sample solutions heated for time 0 and time t, respectively.

Results and discussion

Interaction of diazoresin and SDS in aqueous solution

The interaction of diazoresin and SDS in aqueous solution with different mole ratios SDS/-N: was investigated. In the case of SDS/-Nl < 0.5, the reaction can be represented as follows:

H. Luo, B. Yang, L. Yang, W. Cao

I N H t NaHSO, t C12HES04Na - Y H Q N,+HSO,-

Diazoresin with HSO; as anion (soluble in water)

Diazoresin with SDB as anion (insoluble in water)

In this region the diazoresin is precipitated continu- ously from the solution with addition of SDS and the absorbance of the solution decreases gradually from 2.4 to about 0.3. In the case of SDS/-N,+ > 1 .O, with addition of SDS the absorbance of the solution increases from 0.3 to more than 2.0 until the precipitate is dissolved completely. The profile of the solution-absorbance changing with SDS/-N: is shown in Fig. 1.

The observation that the precipitate is dissolved in the solution with SDS/-N,+ > 1.0 is considered to be ascribable to the hydrophobic interaction of SDS bound on the diazoresin and free SDS in solution. The dissolving pro- cess is proposed preliminary as follows:

(not dissolved in water) (dissolved in water)

From Fig. 1 we can see that the minimum absorbance appears at SDS/-N: = 0.5 rather than 1.0, i.e., when about 50% of the diazonium groups have reacted with SDS, the diazoresin precipitates from the solution almost completely; then, with more addition of SDS (SDS/ -N: > 1 .O) the diazoresin dissolves again in water.

sl a 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

SDS / -N2+ (mol/mol)

Corrected absorbance of the solution vs. mole ratio of Fig. 1 . SDS/-Nl

Interaction of a diazoresin with sodium dodecyl sulfate in aqueous solution 293

Wavelength / nm Fig. 2. Photodecomposition of diazoresin in SDS-containing aqueous solution under UV irradiation with a 80 W medium pressure mercury lamp at a distance of 9 cm; aqueous solution with 4 x lo-' M -Nl and 0.15 M SDS; irradiation time in s: (top to bottom) 0, 10,20,30,40,50

Photodecomposition of diazoresin in SDS-containing aqueous solution The diazoresin in SDS-containing aqueous solution exhibits a high photosensitivity as shown in Fig. 2.

The diazoresin undergoes an almost complete decomposition within 1 min at these experimental conditions.

The photodecomposition of the diazoresin is a unimo- lecular reaction and should follow the kinetics of a first order reaction. Because the concentration of diazoresin is proportional to its absorbance (Beer-Lambert law), the rate constant kd of the decomposition can be calculated according to the equation:

ln(Ao/A,) = k d . t (4)

where A. and A, represent the absorbance of the solution at time 0 and time t , respectively.

According to the data from Fig. 1, kd of diazoresin in aqueous solution containing 0.15 M SDS is calculated to be kd = 4.27 x s-'. The corresponding half life period is tl12 = 16.2 s according to tIl2 = In 2/kd.

Thermal decomposition of diazoresin in SDS- containing aqueous solution The thermal decomposition is considered to be a key property for practical applications because the storage life of the materials mainly depends on this property.

In SDS-containing aqueous solution, water and 2-methoxyethanol (ME), the kinetics of the thermal decomposition of diazoresin were also investigated and the determined corresponding kd and t112 values are listed in Tab. 1.

t112 increases from 35 min (in HzO), 30.1 rnin (in ME) to 201 min in SDS-containing aqueous solution (SDS/ -N: = 3.5) at pH = 7.0.

Tab. 1. kd and tIl2 for the thermal decomposition of diazoresin in different solutions at 70 "C, pH = 7.0

Solution kd * - t l / 2

min-' min

HzO as solvent 19.80 35.0 ME as solvent 23.02 30.1

SDS-containing aqueous solutiona) 3.45 201.0

a) SDS/-N: = 3.5.

The excellent thermostability of diazoresin in SDS solution is considered to be ascribable to the aggregation behavior of the SDS molecules. The SDS molecules sur- rounding the diazonium group of the resin should protect the -Nl group from an attack by the nucleophiles.

The thermal decomposition of diazoresin is accelerated by a nucleophilic substitution. A well-known fact is that the thermostability of diazoresin under acidic conditions is much better than under alkalic conditions because the acid suppresses the formation of HO- in water or RO- in alcohols. Under alkalic conditions the decomposition of diazoresin is so rapid that the nitrogen bubbles formed by the decomposition are directly visible. It is noteworthy that the diazoresin both in solid and in solution should be stored under acidic conditions.

The effect of the concentration of SDS on the thermostability of the diazoresin in aqueous solution has been investigated; k d and t1/2 determined for different SDS/ -Nl mole ratios are listed in Tab. 2.

The results show that in the region of SDSI-N; = 1- 5, the effect of SDS concentration on the thermostability of the diazoresin is remarkable.

Tab. 2. kd and tln for the thermal decomposition of diazoresin in aqueous solutions with different SDS/-Ni mole ratios at 70°C, pH = 7.0

SDS/-N: kd * lo-' - t l / 2

min-' min

0 19.80 35 1 .o 10.04 69 3.5 3.45 20 1 5.3 2.67 259 7.1 2.73 254

17.7 2.88 240

Photoimaging characteristics of the DR-SDS system The solubility of diazoresin at room temperature in a 0.15 M SDS aqueous solution reaches more than 5 wt.-% and can be used directly for coating. On an aluminium plate with hydrophilic surface obtained from anodic oxi- dation, the DR-SDS aqueous solution was coated, dried in the dark to form a photosensitive film (1 -2 pm thick- ness) and exposed through a photographic film with a 300 W medium pressure mercury lamp at a distance of

H. Luo, B. Yang, L. Yang, W. Cao

30 cm for 2 min; then the film was developed in water. The unexposed area was dissolved while the exposed area remained due to the formation of a crosslinking structure. The crosslinking reaction under irradiation is ascribed to a reaction of the hydroxyl groups, attached on the diazoresin molecule as end-groups, with the diazonium group to form the crosslinking structurez3). A clear imaging was obtained, adhering strongly to the surface of the plate. The image part which is of hydrophobic nature accepts ink easily whereas the nonimaging part, i.e. the aluminum surface, is hydrophilic and accepts water only. This characteristics of DR-SDS should be very interesting for printing techniques.

Conclusion The interactions of diazoresin and SDS in aqueous solution take place in two different manners according to the mole ratio of SDS/-Nl: in the case of SDS/-Nl c 0.5 the diazoresin reacts with SDS to form a precipitate, while in the case of SDS/-N: > 1.0 the precipitate dissolves gradually until a homogeneous solution forms.

The dissoluble character of diazoresin-SDS complexes in aqueous solution can be ascribed to an aggregation of SDS molecules via hydrophobic interactions. From the investigation of thermal and photo-decomposition, it was found that the thermal stability of diazoresin is much better in SDS-containing aqueous solution than in water or in 2-methoxyethanol. The half life period of decomposition f112 rises from 35.0 min in water, 30.1 min in ME to 201 min in SDS-containing aqueous solution (SDS/-Nl = 3.5) at pH = 7.0, but the photo-sensitivity does not decrease. A composition of the diazoresin and SDS in aqueous solution has been prepared and was used to prepare a photosensitive coating.

Acknowledgement: The project (59633 110) was supported by the National Natural Science Foundation of China.

’) K. Chari, B. Antalek, M. Y. Lin, S. K. Sinha, J. Chem. Phys.

2, H. G. Schild, D. A. Tirrell, Langmuir 7,665 (1991) 3, E. Hecht, H. Hoffrnann, Langmuir 10,86 (1994) 4, M. Alrngren, J. Van Stam, C. Lindblad, R. Li, P. Stilbe, P.

Bahadur, J. Phys. Chem. 95,5677 (1991) N. Isogai, J. P. Gong, Y. Osada, Macromolecules 29, 6803 (1996)

6, T. Seki, A. Tohnai, T. Tamaki, A. Kaito, Macromolecules 29, 4813 (1996)

7, H. Okuzaki, Y. Osada, Macromolecules, 28,4554 (1995) 8, M. Antonietti, A. Thuenemann, Colloid Interface Sci. 1, 667

9, C. K. Ober, G. Wegner, Adv. Mate,: (Weinheim, Ge,:) 9, 17

lo) J. Fundin, W. Brown, M. S . Vethamuthu, Macromolecules 29,

11) E. A. Ponornarenko, A. J. Waddon, K. N. Bakeev, D. A. Tir-

12) A. Harada, S . Nozakura, Polym. Bull. (Berlin) 11, 175 (1984) 13) J. Francois, J. Dayantis, J. Sabbadin, Eu,: Polym. J. 21, 165

14) R. Walter, J. Ricka, Ch. Quellet, R. Nyffenegger, Th. Binkert,

15) P. Taylo, Colloid Polym. Sci. 274, 1071(1996) 16) M. Henriquez, E. Abuin, E. Lissi, Colloid Polym. Sci. 271,

17) M. Henriquez, E. Lissi, E. Abuin, Macromolecules 27, 6834

18) M. Antonietti, D. Radloff, U. Wiesner, H. W. Spiess, Macro-

19) J. Fundin, P. Hansson, W. Brown, I. Lidegram, Macromole-

’O) K. Richau, H. H. Schwarz, R. Apostel, J. Memb,: Sci. 113,31

21) S . Yu, Doctoral thesis, Peking University, 1997 ”) M. Antonietti, R. Kublickas, 0. Nuyken, B. Voit, Macromol.

z3) S . Cao, C. Zhao, W. Cao, Polym. Int. 45, 142 (1998)

100,5294 (1994)

(1996)

(1 997)

1195 (1996)

rell, W. J. Macknight, Macromolecules 29,4340 (1996)

(1985)

Macromolecules 29,4019 (1996)

960 (1 993)

( 1994)

mol. Chem. Phys. 197,2713 (1996)

cules 30, 11 18 ( 1997)

( 1996)

Rapid Commun. 18,287 (1997)

interaction of a diazoresin with sodium dodecyl sulfate in aqueous solution

Documents