Polymeric Surfactants Based on Oleic Acid. II.Copolymerization of Sodium Acrylamidostearate and 10-Undecen-1-ol in a Lamellar Liquid Crystal

FANG LI,1 ZHIQIANG ZHANG,1 STIG E. FRIBERG,1 PATRICIA A. AIKENS2

1 Department of Chemistry, Clarkson University, Potsdam, NY 13699-5810

2 Uniqema, Concord Plaza, Bedford Bldg., Wilmington, DE 19850-5391

Received 9 November 1998; revised 15 February 1999

ABSTRACT: Copolymerization of sodium acrylamidostearate (NaAAS) and 10-undecen-1-ol (UdOH) was performed in the lamellar liquid crystal (LLC) formed by NaAAS,UdOH, and water. After the polymerization the lamellar structure remained, and thedisorder of the lamellar liquid crystal was, to some extent, reduced. Surface tension,small-angle X-ray diffraction, dynamic light scattering, viscosity, and fluorescencemethods were used to study the properties of the copolymer. The polymeric surfactantbehaves like polyelectrolyte and is more surface active than its precursor, i.e., NaAAS.The polymeric surfactant is capable of forming uni-molecular micelles through coilingof its hydrophobic chains. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37:2863–2872, 1999Keywords: copolymers; surfactants; lamellar liquid crystal; micelles; surface tension

INTRODUCTION

Oleic acid is one of most common fatty acids, withone double bond in the middle of a long hydrocar-bon chain. The polymerization of oleic acid doesnot yield polymer of very high molecular weightdue to an autoinhibition effect resulting from thepresence of allylic hydrogen in the molecule.1 Ourprevious contribution2 and other articles3,4 haveshown that only low-molecular-weight oligomercan be formed through the polymerization of oleicacid. Hence, a number of polymerization stud-ies5,6 have been performed on the chemicallymodified oleic acid—sodium acrylamidostearate,in which the acrylamide side group is attached tothe stearic chain at the carbon atom that hasallylic hydrogen present in oleic acid.

Polymerization in amphiphilic associationstructures has attracted great interest because ofthe potential to prepare small uniform latex par-ticles of water-soluble polymers7,8 or to preparehighly porous latex particles.9 The research hasbeen mostly focused on the polymerization in mi-croemulsions10–14 and lyotropic liquid crystalshave received limited interest. Very earlywork15,16 was followed by a few publications17,18

and later by extensive investigations by Finkel-mann and coworkers,19–22 Anderson and Strom,23

Yang and Wegner,24,25 and others.26,27 Finkel-mann and coworkers19–22 demonstrated that po-lymerization actually stabilized the long-rangeorder of the liquid crystal, and Anderson success-fully prepared a structure with extremely well-defined pores using the polymerization of cubicliquid crystals. Valuable information about reac-tions in liquid crystalline media was provided byPercec, Jonsson, and Tomazos in their extensivereview article,28 although it was mainly focusedupon thermotropic liquid crystals. Moreover,

Correspondence to: S. E. Friberg (E-mail: FBG@agent.clarkson.edu)Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 37, 2863–2872 (1999)© 1999 John Wiley & Sons, Inc. CCC 0887-624X/99/152863-10

2863

Friberg and coworkers29–31 extended the scope ofinvestigations of polymerization from water-based liquid crystals to nonaqueous ones.

But until now, there were only few reports30–32

dealing with the properties of the thus-preparedpolymer products. In this paper, we copolymerizedsodium acrylamidostearate (NaAAS) and 10-unde-cen-1-ol (UdOH) in the lamellar liquid crystal (LLC)formed by NaAAS, UdOH, and water, and the prop-erties of the copolymer product were investigated bysurface tension, small-angle X-ray diffraction, fluo-rescence, and viscosity methods.

EXPERIMENTAL

Materials

Oleic acid (95%) was purchased from Fisher Sci-entific (Pittsburgh, PA). Sulfuric acid (96.5%) wasfrom J. T. Baker Co. (Phillipsburg, NJ). Acryloni-trile, 10-undecen-1-ol, acetone, ethanol, cyclohex-ane, carbon tetrachloride, and sodium were allobtained from Aldrich (Milwaukee, WI) and wereof purity greater than 99%. Water was deionizedand doubly distilled.

Synthesis of the Polymerizable Surfactant

The polymerizable surfactant sodium acrylam-idostearate (NaAAS) was prepared according tothe modified Ritter reaction.33 In a 500 mL three-necked flask equipped with a stirrer, a condenser,and a dropping funnel were placed 121 g of 96.5%sulfuric acid. With the temperature around 0°C,53 g acrylonitrile and 70.5 g oleic acid were care-fully added. The mixture was stirred below 15°Cfor 15 h and kept overnight. The acrylamidoste-aric acid was obtained after water rinses (at 0°C)and extraction of the unreacted organic materialwith carbon tretrachloride. A final extraction wasmade with cyclohexane to remove trace amountsof carbon tetrachloride. The NaAAS was preparedby neutralizing the ethanol solution of acrylam-idostearate acid with the stoichiometric amountof sodium ethoxide to pH around 10, using bro-mothymol blue as the indicator. After drying invacuum, a yellow powder of NaAAS was obtained.Its infrared absorption [Figure 1(A)] at 3,075 and1,625 cm21 were due to the terminal vinyl group(CH2ACHO) while the 3,273, 1,654, and 1,560cm21 peaks arose from the absorption of amidegroup (OCONHO).5,34

Determination of Phase Regions

The one-phase regions of the system (NaAAS/UdOH/Water) are determined by optical observa-tion of the samples both visually and with the aidof a microscope equipped with crossed polarizers.The boundary line of the liquid crystal region waschecked by small-angle X-ray diffraction.

Copolymerization of NaAAS with UdOH

The copolymerization of NaAAS with UdOH inliquid crystal, initiated by 1 wt % AIBN (based onthe total weight of NaAAS and UdOH), was car-ried out in a series of sealed glass tubes. The glasstubes were deoxygened by nitrogen gas purgingand then kept in a 60°C water bath without agi-tation for 12 h. After polymerization, the lamellarliquid crystal was dispersed in an excess of water.A small amount of oil was found on top of thewater, indicating that the monomer UdOH didundergo reaction in the process. It was collected

Figure 1. Infrared spectra of sodium acrylamidoste-arate (A) and the LLC copolymer of sodium acrylam-idostearate with 10-undecen-1-ol (B).

2864 LI ET AL.

and weighed in order to estimate the conversionof polymerization (slight solubility of water inUdOH was taken into consideration; UdOH hasnearly no solubility in water), which was above80%. The aqueous phase, together with the pre-cipitate, was put into vacuum oven at 60°C untilmost of the water evaporated and a paste wasobtained. The paste was washed thoroughly withdry ethanol to remove unreacted monomers, anddried in the vacuum oven to obtain the copolymerproduct.

Optical Microscopy

A small amount of the sample was deposited be-tween a glass plate and cover slide to form a thinfilm observed by an Olympus microscope (ModelBHA-P) equipped with crossed polarizers, and thephotographs were obtained with a Polaroid micro-camera.

Small-angle X-ray Diffraction

A small amount of the sample was drawn into afine glass capillary tube (0.7 mm) and placed in abrass sample holder. The diffraction pattern wasobtained from a Kiessig small-angle camera(Richard Seifert) and an ORDELA detection sys-tem. Lead stearate with an interlayer spacing of4.82 nm was used as the calibration standard.

Infrared (IR) Spectroscopy

The IR spectra of the polymerizable surfactantNaAAS and the its copolymerized product wereobtained from KBr pellets of the copolymer prod-uct with water removed completely. The spectrawere recorded on a Mattson Galaxy 202 Fouriertransform infrared spectrometer.

1H-NMR1H-NMR spectra were obtained through a BrukerAC250 Fourier transform nuclear magnetic reso-nance spectrometer (250 MHz), with samples dis-solved in D2O.

UV Spectra

NaAAS and the copolymer of NaAAS and UdOHwere dissolved in water and then the UV spectrawere recorded on an HP 5452A Diode Array Spec-trophotometer at 23 60.2°C.

Surface Tension

The equilibrium surface tension of aqueous solu-tion of NaAAS and its copolymers with UdOHwas measured using a Fisher Model 21 SurfaceTensiomat at 23 6 0.2°C.

Viscosity Measurements

The reduced viscosity of the aqueous solutions ofthe copolymer product was measured with an Ub-belohde dilution viscometer at 23 6 0.2°C.

Dynamic Light Scattering (DLS)

Light scattering measurements were performedon a Brookhaven Instrument system. The lightsource is an argon ion laser (Model 85, LexelLaser) operating at a wavelength of 514.5 nm.The samples were dissolved in 0.7 mol/L NaClsolution to screen the effect of counterions, andfiltered through 0.2 mm Whatman filters to elim-inate dust particles before measurements. Intensitycorrelation data were analyzed by the CONTINmethod. The measured diffusion coefficients wererepresented in terms of apparent radii by usingStokes equation and assuming the solvent to havethe viscosity of the NaCl solution.

Spectrofluorimetry

The fluorescence emission spectra of pyrene solu-bilized in aqueous solutions of the copolymerproducts were recorded as a function of polymerconcentration using an LS 50B Perkin-Elmer Lu-minescence Spectrometer at an excitation wave-length of 335 nm. The ratio of I1/I3 of the intensi-ties of the first and the third vibronic peaks in theemission spectrum of unimeric pyrene providesan estimate of the polarity sensed by pyrene in itsenvironment.35

Molecular Modeling

Geometry optimization of the model molecule wasperformed on an IBM workstation by molecularmechanics method using the software SPARTANIBM version 5.0.3.

RESULTS AND DISCUSSION

Phase Diagram and Structure Changes of theLiquid Crystal before and after Copolymerization

The phase diagram of NaAAS, UdOH, and wateris shown in Figure 2. Three one-phase regions

POLYMER SURFACTANTS BASED ON OLEIC ACID 2865

were found in the phase diagram: a liquid crystalregion, a W/O microemulsion region, and an O/Wmicroemulsion region.

Shown in Figure 3(A) is the microscope photo-graph of the sample marked as “c” in Figure 2viewed between crossed polarizers. The typical“oily steak” and maltese crosses textures showthat the liquid crystal in the phase diagram to belamellar. Samples with compositions on thestraight line through the liquid crystal region to-wards the water corner (Fig. 2) were prepared forthe measurement of small-angle X-ray diffractionwith different amount of hexane added. The in-terlayer spacing of the liquid crystals plottedagainst the volume ratio of water is presented inFigure 4. The interlayer spacing at zero watercontent, d0, is plotted against the volume ratio ofhexane as shown in the inset of Figure 4, whichincreases with increasing the hexane content, in-dicating that hexane is solubilized in the regionbetween the end methyl groups of the hydrocar-bon chain. The slope of the straight line does notchange very much with the content of the solubi-lized hexane. According to eq. (1),36 we know thatthe increase of hexane content between the hy-drocarbon chain has little influence on the frac-tion of water penetration (a) from the water zoneto the hydrophobic region.

d 5 d0@1 1 ~1 2 a!R# (1)

After polymerization the liquid crystals retainthe lamellar structures, as can be seen from the

microphoto of Figure 3(B). The IR spectrum of thecopolymer product (point c in Fig. 2) after hexaneand water were removed is shown in Figure 1(B).The absorption peaks at 3,075 and 1,625 cm21

corresponding to the terminal vinyl group almostdisappear after copolymerization.

Figure 5 is the proton NMR spectra of NaAASand NaAAS/UdOH (weight ratio 4 : 1) before andafter copolymerization. In the NaAAS spectrum

Figure 3. Microscope photographs of the samplemarked as “c” in Figure 2 before (A) and after polymer-ization (B). Crossed polarizers, magnification 200.

Figure 2. One-phase regions in the system of sodiumacrylamidostearate (NaAAS)/10-undecen-1-ol (UdOH)/H2O.

2866 LI ET AL.

[Fig. 5(A)], the multiple peaks of vinyl protons(CH2ACHO) at d6.21 as well as d5.61, and theNOH proton at d3.90, are found.5,37 A group ofmultiple peaks centered at d1.4 arise from theprotons of alkyl chain of NaAAS, and the proton ofthe terminal methyl gives the signal at d0.85. Thesignal at d4.63 is due to D2O. Adding UdOH toNaAAS results in two new peaks in the NMRspectrum [Fig. 5(B)], one at d1.79 arising from thehydrogen of the a carbon atom of the double bondin UdOH, and the other at d3.5 for the hydrogenof OOH group. After the copolymerization thepeaks of vinyl protons at d6.21 as well as d5.61almost disappear, all the other peaks [Fig. 5(C)]remain same as those of NaAAS/UdOH.

The UV spectra in Figure 6 showed that theUV absorption in 226 nm due to the conjugation ofO(CAO)OCHACH2 almost disappears after thecopolymerization because of the loss of the conju-gated link.

Combining the information obtained from IR,1H-NMR, and UV spectra, a conclusion that copo-lymerization does take place in LLC phase is rea-sonable. In addition very small amount of UdOHwas separated from the product (vide supra), giv-

ing a conversion of polymerization of UdOH above80%. In the present system, the weight ratio ofNaAAS/UdOH is 4:1, which corresponds to a mo-lar ratio of 1:0.55. We are aware that the acryl-amido group of NaAAS is more reactive than thepolymerizable function of UdOH.1 However, inthe lamellar structure of liquid crystalline phase,the movement of molecules is severely restrictedperpendicular to the planes and only lateralmovement of the constituent molecules takesplace. Hence, the situation is significantly differ-ent from that in a disordered bulk phase andcopolymerization actually takes place betweenmonomers with different reaction ratios.30,31 Theliquid crystals were well-mixed to ensure equilib-rium structure before the polymerization, andtheir structure was kept at 60°C. Therefore, the 1: 0.55 molar ratio would suggest that in the liquidcrystalline phase the NaAAS and UdOH mole-cules are, statistically, arranged close to a 2 : 1ratio. Steric hindrance would not play a signifi-cant role during the reaction process since double

Figure 5. Proton NMR spectra of sodium acrylam-idostearate (A); sodium acrylamidostearate/10-unde-cen-1-ol at a weight ratio of 4 : 1 (B); and the LLCcopolymer of sodium acrylamidostearate with 10-unde-cen-1-ol (C); in D2O.

Figure 4. Interlayer spacing as a function of thevolume ratio of water of the lamellar liquid crystal inFigure 2 with different amount of hexane added. Theweight ratio of sodium acrylamidostearate to 10-unde-cen-1-ol is 4 : 1. ■: before polymerization and withouthexane; F: before polymerization and with 10% hexane;h: before polymerization and with 20% hexane; E: afterpolymerization and with 20% hexane. Inset: Interlayerspacing at zero water content (d0) plotted against thevolume of hexane. Œ: before polymerization; ‚: afterpolymerization.

POLYMER SURFACTANTS BASED ON OLEIC ACID 2867

bonds in both molecules are in the end position.Although the above interpretation is not fullyproven, the agreement of the data obtained fromthe molecular modeling and from the surface ten-sion measurements (vide infra) forms a strongsupport. Future analysis is planned to obtainmore information to establish a better under-standing of the molecular structure of the copol-ymer.

Figure 4 showed that the interlayer space in-creases after the copolymerization in the lamellarliquid crystals. The interlayer spacing at zero watercontent with 20% hexane added changes from 33.7Å to 38.2 Å, the inset of Figure 4. The molecularlength of stearic acid is around 23.5 Å.38,39 There-fore the minimum length of two layer of NaAASmolecules should be around 47 Å if the NaAASmolecules extend completely straight. In fact, theinterlayer spacing is 27.5 Å with the absence of hex-ane, indicating that from around the tenthcarbon atom, the hydrocarbon chain of the NaAASmolecules becomes disordered [Fig. 7(A)].40 Af-ter polymerization, the ONHO(CAO)OCHACH2moiety is connected directly to the UdOH mole-cule, and the space between UdOH hydrocarbonchain and the stearic chain is reduced. Hence inthe liquid crystalline phase the movement of thetail of the stearic chain is restricted resulting inenhanced ordering as is obvious from the in-creased interlayer spacing. In addition water doesnot penetrate from the water zone to the hydro-

phobic region to the same extent as before, adecreased from 0.43 to 0.33. The possible struc-tures of the lamellar liquid crystal before andafter copolymerization are schematically depictedin Figure 7.

The cross section area occupied by each amphi-phile molecule in the lamellar liquid crystal be-fore and after polymerization is estimated accord-ing to the following equation:

ALLC 51r

2MNAd00

3 1024 ~Å2/molecule! (2)

r (in g/cm3) and M are the density and averagemolecular weight of the amphiphile, NA is theAvogadro number, and d00 (in Å) is the interlayerspacing at zero water content in the absence ofhydrocarbons. Taking r as 0.90 g/cm,3 ALLC be-comes 41.2 Å2 per molecule before polymeriza-tion, and after polymerization ALLC is 1993 Å2 percopolymer molecule (the molecular weight of thecopolymer as 16,500 is used according to the fol-lowing viscosity measurement). The area occu-pied by one unit of the copolymer, (NaAAS)2/UdOH, in the lamellar liquid crystal is decreasedto 110.7 Å2 after the copolymerization (the copo-lymerization degree of 54 is used which will bediscussed later).

The Property of the Copolymer Product

Before measuring the properties of the copolymerproduct, hexane and water were removed com-pletely.

Figure 6. UV Spectra of sodium acrylamidostearate(A) and the LLC copolymer of sodium acrylamidostear-ate with 10-undecen-1-ol (B) in water.

Figure 7. Schematic drawing of the possible struc-tures of the lamellar liquid crystals. A: before polymer-ization; B: after polymerization.

2868 LI ET AL.

Figure 8 gives the reduced viscosity of the LLCcopolymer product as a function of the concentra-tion of the aqueous polymer solution. The reducedviscosity increased strongly with decreasing poly-mer concentration. This typical polyelectrolytebehavior, usually observed in salt-free aqueoussolutions,41 occurs because the carboxylic acidgroup in the polymer side chain ionizes in theaqueous solution, and the electrostatic repulsionmakes this copolymer chain highly extended.

The empirical Fuoss equation (3) is usuallyapplied to interpret the electrostatic interactionof polyelectrolytes in aqueous solutions.42 Figure8 also depicts (hsp/C)21

~hsp/C!21 5 a 1 b C1/2 ~a and b are two constants!(3)

plotted against C1/2, which is in good accordancewith the Fuoss equation (3); the linear relationcan be established for the copolymer in very diluteregion.

Since the structure of sodium 11-(N-ethylacryl-amido)undecanoate (Na 11-EAAU) is very similarto NaAAS,43 the empirical Mark—Houwink equa-tion of poly(Na 11-EAAU) established by Yeoh etal.,43 obtained for the aqueous polymer solution ofdifferent ionic strengths, was employed withoutmodification to calculate the molecular weight ofthe copolymer of the present research:

@h# 5 3.36 3 1025 Mw0.69 (4)

where [h] is the intrinsic viscosity of the polymerin 0.7 mol/L NaCl solution, and MW is the molec-

ular weight of the polymer. The molecular weightof our copolymer is estimated as approximately16,500. Assuming NaAAS is copolymerized withUdOH at a molar ratio of 2 : 1, then the degree ofcopolymerization becomes 54, giving 36 NaAASmolecules per polymer molecule.

The dynamic light scattering result of the 0.2g/L aqueous solution of the copolymer in 0.7 mol/LNaCl solution, Figure 9, indicates that large sizeparticles (around 9–11 nm) exist in the its aque-ous solution even at this low concentration, whichis not unreasonable considering the polymeriza-tion degree obtained above. Further efforts forinterpretation of the solution structure of the co-polymer is in progress.

Figure 10 shows the surface tension measure-ments of NaAAS and the LLC copolymer. Afterpolymerization, the minimum surface tension atequilibrium conditions was reduced from 37.5mN/m of NaAAS to 27.5 mN/m of the copolymer,showing that the polymerized surfactant is moresurface active.

The Gibbs adsorption equation of an anionicsurfactant (NaR) can be written as

2dg

RT 5 Oi

Gidlnai 5 GNa1dlnaNa1 1 GR2dlnaR2

(5)

where GNa1 and GR2 are the surface excesses forNa1 and R2, respectively, and aNa1 and aR2 arethe corresponding activities. If there is no second

Figure 9. Dynamic light scattering result of the so-dium acrylamidostearate/10-undecen-1-ol copolymerproduct (0.2 g/L in 0.7 mol/L NaCl solution).

Figure 8. Dependence of the reduced viscosity onconcentration of the sodium acrylamidostearate/10-un-decen-1-ol copolymer product in water.

POLYMER SURFACTANTS BASED ON OLEIC ACID 2869

electrolyte NaX present in the aqueous NaR solu-tion, then

2dg

RT 5 2GR2dlnaR2 < 2GR2dlnCR2 (6)

For the copolymer (NanR), GNa1 5 nGR2 (where n5 36), the Gibbs adsorption equation becomes

2dg

RT 5 ~n 1 1!GR2dlnaR2 < ~n 1 1!GR2dlnCR2

(7)

From the surface tension versus ln C curve, Fig-ure 10, the saturated adsorption values Gmax andminimum area per molecule Amin before and aftercopolymerization can be obtained, which arelisted in Table I. After copolymerization, Gmaxvalue becomes smaller than that of NaAAS, whilethe minimum area per molecule is, as expected,much larger than that of NaAAS. If the copoly-merization degree is considered, the average areaoccupied by a (NaAAS)2/UdOH unit becomes

123.1 Å2 (i.e., 41.0 Å2 per monomer), showing thatthe distance between the NaAAS and UdOH moi-eties in the copolymer is smaller than that be-tween two NaAAS molecules at the air-water in-terface. In order to prove this fact, geometry op-timization of model molecule was performedusing the molecular mechanics method, in whichthe headgroups of the copolymer molecules arelocated at, or at least near, the air-water inter-face, and therefore restricted within a certain dis-tance with each other. To mimic this environ-ment, the distance between the carboxylate car-bon of NaAAS and the carbon in the end of UdOHconnected with the hydroxyl group is restrainedwithin 5 Å. After performing of the geometry op-timization, the final partial structure of the copol-ymer molecule containing 4 NaAAS moieties and2 UdOH moieties is shown in Figure 11. Now thecarboxylate and hydroxyl groups are pointing inone direction, towards the air-water interface inthe aqueous solution. The area covered by thispart of the polymer molecule, from the top view,can be given by the SPARTAN software as about22.6 3 10.8 5 244 Å2. Considering that there are36 NaAAS moieties and 18 UdOH ones in onecopolymer molecule, we can easily estimate thearea occupied by a copolymer molecule in theair-water interface, which is 244 3 (36/4) 5 2196Å2, in good agreement with the value obtainedfrom the surface tension measurement.

Through comparison with the data in lamellarliquid crystal, one can find that before polymer-ization, NaAAS and UdOH molecules arrangemore closely with each other in the liquid crystalthan NaAAS molecules do with each other at theair-water interface, but after copolymerization,the area occupied by every NaAAS/UdOH unit atthe air-water interface is nearly the same as thatin the liquid crystal. Because of the direct connec-tion between NaAAS and UdOH molecules afterthe copolymerization, the space between NaAASand UdOH is restricted and the distance betweenthe NaAAS and UdOH moieties is kept constantboth in the lamellar liquid crystal and at theair-water interface.

Figure 10. Plots of surface tension vs. log concentra-tion (in g/L) of sodium acrylamidostearate (h) and thesodium acrylamidostearate/10-undecen-1-ol LLC copol-ymer (E).

Table I. Surface Properties of NaAAS and the LLC Copolymer

CMC(g/L) CMC (M)

gCMC

(mN/m)1026Gmax

(mol/Å2)Amin

(Å2/molecule)

NaAAS 0.554 1.48 3 1023 37.5 1.186 140Copolymer 1.083 6.56 3 1025 27.5 0.075 2215

2870 LI ET AL.

It is well known that the fluorescence spectrumof pyrene provides an indication of the polarity ofthe microenvironment.35,44 There are five peaksin the steady state fluorescence spectrum ofpyrene unimer: the third peak is not sensitive tothe environment, but the first peak becomes veryweak in a non-polar environment.44 Plotted inFigure 12 is the intensity ratio of the two peaks ofpyrene, I1/I3, against the concentration of NaAASand the copolymer in water. With the increase ofthe surfactant concentration, the I1/I3 value de-creases. After a certain concentration, the de-creasing tendency becomes more pronounced, re-vealing a change of the polarity of the pyreneenvironment. Usually after the formation of mi-celles, the pyrene molecules will be located in themicellar hydrophobic center or in the palisadelayer,44 where they experience a hydrophobic en-vironment. Hence the I1/I3 value decreases morerapidly after the formation of micelles. The criti-cal micellization concentration (CMC) obtainedfrom the fluorescence measurement, Figure 12,agrees well with that from the surface tensionmethod, Figure 10. Figure 12 also shows that,before the micellar formation, there is a distinct

difference of the I1/I3 values between NaAAS andcopolymer. The ratio of the aqueous copolymersolution is significantly smaller than that ofNaAAS, showing that even before the formationof (multi-molecular) micelles, there exists a hy-drophobic environment for pyrene in the copoly-mer solution. We assume this to be due to theuni-molecular polymer micelles.45 On the con-trary, in the NaAAS system, before the formationof normal micelles, the probe resides mainly inthe aqueous phase, a highly polar environment.

SUMMARY

Sodium acrylamidostearate (NaAAS) and 10-un-decen-1-ol (UdOH) were copolymerized in the la-mellar liquid crystal (LLC) formed by NaAAS,UdOH, and water. The lamellar structure re-mained after the polymerization, while the inter-layer spacing increased and the water penetra-tion coefficient decreased. Before polymerization,the NaAAS and UdOH molecules arrange moreclosely with each other in liquid crystal than theydo at the air-water interface, but after the copo-lymerization, the area occupied by each(NaAAS)2/UdOH unit at the air-water interface isof the same magnitude as that in lamellar liquidcrystal.

This research was financed in part by ICI Surfactants(now Uniqema), Wilmington, DE through a grant from

Figure 12. Variation of I1/I3 of the pyrene fluores-cence with the concentration of sodium acrylamidoste-arate (h) and the LLC copolymer (E) in water.

Figure 11. Optimized geometry of a partial struc-ture of the copolymer containing four sodium acrylam-idostearate molecules and two 10-undecen-1-ol mole-cules calculated by the molecular mechanics methodusing SPARTAN 5.0.3. The circles are correspondingto, in the order of decreasing darkness, oxygen, carbon,hydrogen, and nitrogen atoms.

POLYMER SURFACTANTS BASED ON OLEIC ACID 2871

the National Soybean Board. The authors thank thereferees for the valuable comments.

REFERENCES AND NOTES

1. Odian, G. Principles of Polymerization, 2nd ed.;John Wiley & Sons: New York, 1981.

2. Zhang, Z.; Li, F.; Friberg, S.E.; Aikens, P. A. JColloid Interface Sci, to appear.

3. Erhan, S. M.; Kleiman, R.; Isbell, T. A. J Am OilChem Soc 1993, 70, 461.

4. Isbell, T. A.; Kleiman, R.; Plattner, B. A. J Am OilChem Soc 1994, 71, 169.

5. Chew, C. H.; Gan, L. M. J Polym Sci Part A PolymChem 1985, 23, 2225.

6. Rai, W. R. P.; Sasthav, M.; Cheung, H. M. J ApplPolym Sci 1993, 49, 1453.

7. Candau, F.; Zekhnini, F.; Durand, J.-P. J ColloidInterface Sci 1986, 114, 398.

8. Candau, F.; Leong, Y. S.; Fitch, R. M. J Polym SciPart A Polym Chem 1985, 23, 193.

9. Haque, E.; Qutubuddin, S. J Polym Sci Polym LettEd 1988, 26, 429.

10. Rai, W. R. P.; Sasthav, M.; Cheung, H. M. Lang-muir 1991, 7, 2586.

11. Candau, F. In Polymerization in Organized Media;Paleos, C. M., Ed.; Gordon and Breach Sci. Publish-ers: Philadelphia, 1992; pp 215–282.

12. Guo, J. S.; Sudol, E. D.; Vanderhoff, J. W.; El-Aasser, M. S. J Polym Sci Part A Polym Chem1992, 30, 691.

13. Antonietti, M.; Basten, R.; Lohmann, S. MacromolChem Phys 1995, 196, 441.

14. Full, A. P.; Kaler, E. W.; Arellano, J.; Puig, J. E.Macromolecules 1996, 29, 2764.

15. Herz, J.; Reiss-Husson, F.; Rempp, P.; Luzzati, V. JPolym Sci Part C 1964, 4, 1275 (in French).

16. Sadron, C. Pure Appl Chem 1962, 4, 346.17. Friberg, S. E.; Thundathil, R.; Stoffer, J. O. Sci-

ences 1979, 205, 607.18. Thundathil, R.; Stoffer, J. O.; Friberg, S. E. J

Polym Sci Part A Polym Chem 1980, 18, 2629.19. Finkelmann, H.; Koldehof, J.; Ringsdorf, H. Angew

Chem 1978, 90, 992.20. Finkelmann, H.; Luhmann, B.; Rehage, G. Colloid

Polym Sci 1982, 260, 56.21. Jahns, E.; Finkelmann, H. Colloid Polym Sci 1987,

265, 304.22. Luhmann, B.; Finkelmann, H. Colloid Polym Sci

1987, 265, 506.

23. Anderson, D. M.; Strom, P. In Polymer AssociationStructures: Microemulsions and Liquid Crystals;El-Nokaly, M. A., Ed.; ACS Symp. Ser. 384; Amer-ican Chemical Society: Washington, DC, 1989; p204–224.

24. Yang, J.; Wegner, G. Macromolecules 1992, 25,1786.

25. Yang, J.; Wegner, G. Macromolecules 1992, 25,1791.

26. Laversanne, R. Macromolecules 1992, 25, 489.27. McGrath, K. M.; Drummond, C. J. Colloid Polym

Sci 1996, 274, 316.28. Percec, V.; Jonsson, H.; Tomazos, D. In Polymer-

ization in Organized Media; Paleos, C. M., Ed.;Gordon and Breach Sci. Publishers: Philadelphia,1992; p 1–104.

29. Friberg, S. E.; Wohn, C. S.; Lockwood, F. E. Mac-romolecules 1987, 20, 2057.

30. Friberg, S. E.; Yu, B.; Ahmed, A. U.; Campbell,G. A. Colloids Surf 1993, A 69, 239.

31. Friberg, S. E.; Campbell, G. A.; Yu, B. J DispersionSci Techn 1993, 14, 205.

32. Cochin, D.; Candau, F.; Zana, R. Macromoecules1993, 26, 5755.

33. Greene, B. W.; Sheetz, D. P.; Filler, T. D. J ColloidInterface Sci 1970, 32, 90.

34. Nakanishi, K.; Solomon, P. H. Infrared AbsorptionSpectroscopy, 2nd ed.; Holden-Day Inc.: San Fran-cisco, 1977.

35. K. Kalyanasundaram, and J. K. Thomas, J. Am-.Chem. Soc. 99, 2039 (1977).

36. Friberg, S. E.; Yu, B.; Campbell, G. J Polym SciPart A Polym Chem 1990, 28, 3575.

37. Skoog, D. A. Principles of Instrumental Analysis,3rd ed.; Saunders College Publishing: Philadephia,1985.

38. Clark, G. L.; Leppla, P. W. J Am Chem Soc 1936,58, 2199.

39. Umemura, J.; Takeda, S.; Hasegawa, T.; Take-naka, T. J Mol Struct 1993, 297, 57.

40. Friberg, S. E.; Rananavare, S. B.; Osborne, D. W. JColloid Interface Sci 1986, 109, 487.

41. Hara, M.; Lee, A. H.; Wu, J. J Polym Sci Part BPolym Phys 1987, 25, 1407.

42. Fuoss, R. M.; Cathers, G. I. J Polym Sci 1949, 4, 97.43. Yeoh, H. W.; Chew, C. H.; Gan, L. M.; Koh, L. L. J

Macromol Sci Chem 1990, A27, 63.44. Thomas, J. K. Chem Rev 1980, 80, 283.45. Turro, N. J.; Chung, C.-J. Macromolecules 1984,

17, 2123.

2872 LI ET AL.