Langmuir 1996, 12, 6015-6021
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Effects of Solute-Surfactant Interactions on Micelle Formation in Surfactant Solutions Bruce J. Palmer* and Jun Liu Energy and Environmental Sciences Division, Pacific Northwest National Laboratory, Box 999, Richland, Washington 99352 Received June 7, 1996. In Final Form: August 28, 1996X The effect of dissolved solutes on micelle structure is investigated using molecular dynamics simulations. A simple model developed previously for surfactants in aqueous solution is extended to include a simple solute to mimic the effect of dissolved oxide precursors in solution. The solute parameters are chosen so that a pure solute would be in the solid phase under the thermodynamic conditions at which the simulations are run. The interaction energy between the solute and the surfactant head group is systematically varied. The micelle structures are affected by both the magnitude and the orientation dependence of the solute interaction potentials. When the interaction is weak, the solute has little effect on the surfactant structure, but as the interaction is increased, the spherical micelle structures adopted by the surfactant system in the absence of solute are severely distorted. The implications of these results are discussed in terms of the structures formed in complex ceramic-surfactant systems.
1. Introduction Dissolved inorganic solutes, especially solutes that interact strongly with surfactants, have a large effect on the structures and properties of surfactant solutions.1 These phenomena play an important role in many industrial processes.2 For example, there has been considerable interest in using surfactant molecules to control and direct the synthesis of inorganic compounds with well-defined microstructures and morphologies.3 Novel zeolite-like mesoporous molecular sieves have been synthesized based on hexagonal and cubic surfactant aggregates. These materials are characterized by ordered porosity, narrow pore size distribution, and adjustable pore size (from 1.5 to 20 nm).4-6 To understand the formation of these complex materials in surfactant solutions, it is desirable to establish theoretical models that realistically account for both the behavior of the surfactants and the interaction of the surfactants with the condensing solutes. This paper will expand recent work on simple models of surfactants in aqueous solutions to include the effects of dissolved solutes on micelle formation. The interaction of the inorganic precursors with the surfactants and micelles is believed to play a key role in controlling the formation of mesoporous materials, but there is no detailed understanding of how the solute-surfactant interaction affects the final material. From experiments on mesoporous ceramic systems, it is known that the presence of the ceramic precursor can have a large effect on micelle structure and formation.6 The introduction of ceramic precursors has been shown to convert micelles from spherical to rodlike forms.7 Lamellar surfactant strucX Abstract published in Advance ACS Abstracts, November 15, 1996.
(1) Barnickel, P; Wokaun, A. Mol. Phys. 1990, 69, 1. (2) Evans, D. F.; Wennerstrom, H. The Colloidal Domain Where Physics, Chemistry, Biology, and Technology Meet; VCH Publishers, Inc.: New York, 1994; Chapters 4, 6, and 10. (3) Lisiecki, I.; Pileni, M. P. J. Am. Chem. Soc. 1993, 115, 3887. (4) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T-W.; Olson, D. H.; Sheppard, E. W.; McCullen, S. B.; Higgins, J. B.; Schlenker, J. L. J. Am. Chem. Soc. 1992, 114, 10834. (5) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J. Vartuli, J. C.; Beck, J. S. Nature 1992, 359, 710. (6) Monnier, A.; Schuth, F.; Huo, Q.; Kumar, D.; Margolese, D.; Maxwell, R. S.; Stucky, G. D.; Krishnamurthy, M.; Petroff, P.; Firouzi, A.; Janicke, M.; Chmelka, B. F. Science 1993, 261, 1299.
S0743-7463(96)00562-8 CCC: $12.00
tures are also frequently encountered in the synthesis of mesoporous ceramic materials.6 Controlling the micelle structure during synthesis is a key factor in the formation of mesoporous ceramics. The appearance of the wrong micelle structure, particularly the lamellar phases, can severely degrade the properties of the final product. The effect of solutes on micelle formation will be explored by combining a model of surfactant solutions developed previously8 with some simple models for dissolved solutes. The solutes are designed to mimic the behavior of ceramic precursors in solution. The solute parameters are generally chosen so that a system containing only the solute would condense to a solid under the thermodynamic conditions represented by the simulation. Two kinds of solutes are considered. One is characterized by a standard Lennard-Jones interaction, the other is a Lennard-Jones interaction; supplemented by a three-body term to produce a material with local tetrahedral ordering. The parameters governing the solute-solute and solute-head group interactions are varied to study the effects of the different interactions on micelle formation. 2. Surfactant and Solute Models The model surfactant solutions discussed in this paper are similar to those described in a previous study.8 The surfactant molecules are composed of a head site attached to a chain of tail sites, with head sites and tail sites bonded to each other via simple harmonic springs. The different sites along the surfactant chain are also subject to a harmonic bending potential that favors 180° angles in the tail. The solvent and solute particles are composed of a single site. The potential function for the model surfactant solution is of the form N
U)
φij(rij) + ∑ K(θijk - π)2 + ∑ B(rij - R0)2 + ∑ i Rijc (2.2)
The term φ0(Rijc) is a constant chosen so that the pair interaction vanishes at the cutoff potential distance Rijc. Two types of cutoff are used in these calculations. The first is Rijc ) 2.5σij and results in a conventional cut-andshifted Lennard-Jones potential with a potential minimum of approximately ij and a hard-sphere radius of σij. The second is a short-ranged cutoff Rijc ) 21/6σij that gives a purely repulsive, short-ranged potential. All sites in the system, including the solvent, head, tail, and solute sites, interact with each other via a φij(rij) potential The three-body potential U3-body(rij,rjk,θijk) applies only to the solute sites and is similar to the three-body potential proposed by Stillinger and Weber to model the behavior of silicon.9 The three-body term has the form
U3-body(rij,rjk,θijk) ) Ae-γ(rij-σ3)e-γ(rjk-σ3)(cos θijk + 1/3)2 (2.3) where the site indexed by j forms the center of angle θijk. Because of the exponential factors, the three-body terms are fairly short-ranged and their evaluation can be combined with a neighbor list to speed up the calculation. The parameter A controls the magnitude of the interaction, σ3 is an interaction distance at which the three-body term becomes significant, and γ controls the rate of decay of the three-body interaction. The quadratic term containing cos θijk forces the system to favor the tetrahedral angle cos-1(-1/3). Simulations were run for solutes both with and without the three-body interactions. The solvent and surfactant parameters were chosen to mimic the relative energy scales of surfactants in aqueous solution. All parameters are defined in terms of the solvent-solvent interaction parameters and these are set equal to σSS ) 1.0 and SS ) 1.0. (The subscripts S, H, T, and U denote solvent, head, tail, and solute sites, respectively.) The head-head interactions are chosen to be short-range repulsive, and the tail-tail, tail-head, and tail-solvent interactions are all weakly attractive. The head-solvent interaction is comparable to the solventsolvent interaction. These parameters are chosen to represent a charged surfactant head group in aqueous solution attached to a weakly interacting hydrocarbon tail. The head-solvent interaction is chosen to be fairly strong so that the surfactant forms a micelle. If the headsolvent interaction were weak, the surfactant would be more likely to act like a hydrocarbon and the solventsurfactant mixture would most likely separate into two phases. The Lennard-Jones parameters for the surfactant and solvent system are listed in Table 1, along with the solute-solvent and solute-tail interactions. On the basis of previous work, a surfactant tail with six tail sites was chosen. When no solute is present, this system forms (9) Stillinger, F. H.; Weber, A. W. Phys. Rev. B 1985, 31, 5262.
Table 1. Parameters for All the Lennard-Jones Interactions Except the Solute-Head and Solute-Solute Interactions interaction
σ
Rc/σ
SS HS TS HH HT TT US UT
1.0 1.5 1.0 2.0 1.5 1.0 1.0 1.0
1.0 1.0 0.125 1.0 0.125 0.125 1.0 0.125
2.5 2.5 2.5 21/6 2.5 2.5 2.5 2.5
Table 2. Parameters for the Three-Body, Bond Angle Bending, and Bond-Stretching Potentials, as Well as the Particle Masses parameter K B A γ σ3
parameter 10.0 200.0 20.0 5.0 1.0
mH mS mT mU
2.0 1.0 1.0 1.0
spherical micelles at the surfactant concentrations studied in this work.8 The only parameters that were varied in this study were the solute-solute and solute-head group interactions. All other solute parameters were held fixed, aside from the three-body amplitude A, which was set equal to zero for some of the calculations (A ) 0 corresponds to removal of the three-body interactions and reduces the solute to a simple Lennard-Jones interaction). The three-body parameters were chosen so that the solute would be tetrahedrally coordinated in the solid phase instead of being 12-fold coordinated, which is the case for the ordinary Lennard-Jones solid. The three-body parameters, as well as the bond angle bending and bond stretching parameters are listed in Table 2. The bond-stretching parameter B is strong enough so that the root mean square fluctuation in the bond distance from its equilibrium value is about 5%. The nature of the solute was varied by adjusting the Lennard-Jones well depths for the solute-solute and solute-head interactions, as well as by choosing to include or leave out the three-body term in the solute-solute potential. The tendency of the solute to form a solid phase can be controlled by varying the well depth, UU, of the solute-solute interaction. Values of 2.0 and 4.0 were used. These well depths are sufficient to guarantee that a pure Lennard-Jones system would be in the solid phase at the temperature and pressure of these simulations.10 The three-body interactions appear to make the Lennard-Jones effectively more repulsive, and it is not clear that the pure UU ) 2.0 system remains a solid when the three-body interactions are included. The strength of the head-solute is also varied, by changing the well depth, HU. Four combinations of head-solute and solute-solute parameters were investigated. The hard-sphere interaction parameters, σUU and σHU, were the same for all simulations and only the Lennard-Jones well depths were varied. The parameters are summarized in Table 3. Systems A, B, and C represent different strengths of the head-solute interaction for a strong solute-solute interaction, while system D represents both a relatively weak head-solute (10) Hansen, J-P.; Verlet, L. Phys. Rev. 1969, 184, 151. This paper calculates the phase diagram for the Lennard-Jones fluid including the mean-field corrections to the long range part of the potential. However, this is unlikely to lower triple point temperature, estimate to be located at T ) 0.68, by more than 10-20%. Using this value, the triple point temperatures for UU ) 4.0 and UU ) 2.0 are T ) 2.72 and T ) 1.36, respectively.
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Table 3. Lennard-Jones Parameters for the Solute-Head and Solute-Solute Interactionsa
a
system
σHU
σUU
HU
UU
A B C D
1.5 1.5 1.5 1.5
1.0 1.0 1.0 1.0
2.0 4.0 6.0 2.0
4.0 4.0 4.0 2.0
All interactions have a long range cutoff Rc/σ ) 2.5.
and solute-solute interaction. The simulations labeled A, B, C, and D all included the three-body term in the potential. A second set of simulations A′, B′, C′, and D′, were performed without including the three-body term (A ) 0). The trajectories are integrated using the velocity Verlet algorithm recast as a three-point predictor-corrector with a time step of 0.005τ0, where τ0 ) (mSσSS/SS)1/2.11,12 All masses in the system were set equal to 1.0, except for the head group mass, which was set equal to 2.0. The nonbonded interactions were calculated using a linkedcell algorithm to construct a neighbor list.13 The simulations were done under constant temperature-constant pressure conditions, using the Andersen-Nose´ extended system formalism.14,15 Periodic boundary conditions were employed in all simulations. The temperature for all runs was set at kBT/SS ) 0.8, and the pressure was set at P/(SS/ σSS3) ) 0.1. This corresponds to a temperature below the critical point and a pressure above the vapor pressure of the solvent.16 The values of the volume mass MV and the temperature scaling mass MT in the extended system Hamiltonian were set at 0.01 and 1000.0, respectively. Using these parameters, the ratio of the root mean square fluctuations in the Hamiltonian to the average value of the kinetic energy was less than 1 part in 10 000. For this algorithm, such conservation is a good indication that the pressure calculation is being performed correctly. Each simulation contained 100 surfactant molecules, 200 solute molecules, and 3800 solvent molecules. The initial configuration was generated by starting the system at very low density with 100 surfactant and 4000 solvent molecules randomly distributed on a lattice and then allowing the system to condense to a liquid solution using constant pressure-constant temperature molecular dynamics. The initial configuration was taken shortly after the system had condensed, when the distribution of surfactant molecules was still fairly random. The solute molecules were introduced into the system by converting 200 of the solvent molecules to solute molecules and equilibrating for another 100 steps. This configuration was then allowed to evolve under constant pressureconstant temperature conditions in blocks of 50 000 steps. Each of the systems discussed here was allowed to run for a total of 200 000 steps. It is not known whether or not the structures obtained after this many time steps were fully equilibrated. However, the qualitative changes in the systems after 100 000 steps were usually minor. 3. Results The final configurations for the systems with threebody interactions after 200 000 timesteps are shown in Figure 1. To make the structures easier to visualize, four (11) Allen, M. P.; Tildesley, D. J. Computer Simulation of Liquids; Clarendon Press: Oxford, 1987. (12) Palmer, B. J.; Garrett, B. C. J. Chem. Phys. 1993, 98, 4047. (13) Auerbach, D. J.; Paul, W.; Bakker, A. F.; Lutz, C.; Rudge, W. E.; Abraham, F. F. J. Phys. Chem. 1987, 91, 4881. (14) Andersen, H. C. J. Chem. Phys. 1980, 72, 2384. (15) Nose´, S. J. Chem. Phys. 1984, 81, 511. (16) Smith, B. PhD thesis, Rijksuniversiteit Utrecht, The Netherlands, 1990.
copies of the unit cell are shown in each figure. This gives the figures an artificial periodicity that should be ignored. The solvent molecules are not shown. Parts a and d of Figure 1 show well-developed, spherical micelles. Both of these systems are characterized by relatively weak solute-head group interactions (HU ) 2.0 ). System D, shown in Figure 1d, also has a weak solute-solute interaction (UU ) 2.0 ). For system D, the solute does not appear to have aggregated and is uniformly dispersed throughout the system, except in the interior of the micelles. For system A (Figure 1a), the solute-solute interactions are stronger (UU ) 4.0), and the solute in this case appears to have condensed on the surface of the micelles. There is much less free solute in the interstitial regions between micelles in system A than is visible in system D. This may signal the onset of the formation mesoporous materials. As the solute-head interactions are increased (HU ) 4.0, 6.0), there is a distinct change in the surfactant structures. This can be seen by comparing systems A, B, and C, where the solute-head interaction, HU, is increased from 2.0 to 6.0 while the solute-solute interaction, UU, remains fixed. The spherical micelles visible in systems A and D are not evident in systems B and C. Instead, the head groups appear to have been incorporated, along with the solute, into some kind of composite matrix. The formation of this matrix appears unusual, but direct incorporation of surfactants into a growing matrix in experimental systems may occur in the templated growth of zeolitic materials.17 The tendency for the head group to be incorporated into the matrix in this model can probably be controlled through either additional adjustments of the solute-solute interaction parameters or the inclusion of three-body terms into the head-solute interaction. In addition to the incorporation of the head groups into the composite matrix, the tail groups in both systems B and C also appear much more exposed to the solvent than in systems A and D, where the head groups effectively screen the tails from the solvent. The same general trends can be seen for systems A′, B′, C′, and D′, which do not include the three-body interactions. The final configurations for these systems are shown in Figure 2. Well-developed spherical micelles are visible in systems A′ and D′, which both have weak solutehead interactions. For the systems with strong solutehead interactions, B′ and C′, the solutes have completely disrupted the spherical micelles. The head groups are all tightly bound around the particles of condensed solute, while the tail groups are generally bunched together to minimize exposure to the solvent. However, much more of the tails is exposed to the solvent than would be the case in a spherical micelle. The calculations on systems with the strong headsolute interactions (B, C, B′, and C′), both with and without the three-body term, hint at what may be the beginning of a lamellar phase. Both Figures 1c and 2c show small regions that resemble portions of a lipid bilayer. These consist of roughly parallel sheets of head groups with surfactant tails located in between. The tails in these regions are approximately parallel. Similar behavior, although not as pronounced, is also seen in Figures 1b and 2b. Although the systems are too small to determine definitively whether or not a lamellar phase will form, the indications provided by these simulations are intriguing in light of the tendency of mesoporous ceramic systems to form lamellar phases when the ceramic precursors are introduced.18 Under most conditions, it is impossible to (17) Beck, J. S.; Vartuli, J. C. Current Opinion Solid State Mater. Sci. 1996, 1, 76.
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Figure 1. Final configurations for simulations including three-body interactions: (a, top left) system A; (b) system B; (c) system C; (d) system D. The head sites are colored red, the tail sites are colored blue, and the solute particles are yellow. Four copies of the unit cell are dislayed for each configuration.
form anything but the lamellar phase. The simulations suggest that this can be attributed to the tendency of the system to maximize the interfacial area between the micelles and the growing ceramic. Proper control of the interaction of the surfactant head group with the ceramic is therefore an important factor in maintaining the presence of spherical and cylindrical phases during the ceramic synthesis. The absence of three-body interactions has a distinct effect on the shape of the particles of condensed solute. The solute particles visible in Figures 2 are all much more compact and globular than the extended structures seen in the simulations containing the solute three-body terms. Figure 2a-c (systems A′, B′, and C′) is particularly (18) Huo, Q.; Margolese, D. I.; Ciesla, U.; Demuth, D. G.; Feng, P.; Gier, T. E.; Sieger, P.; Firouzi, A.; Chmelka, B. F.; Schu¨th; Stucky, G. D. Chem. Mater. 1994, 6, 1176.
interesting, since the systems represent in increasing solute-head interaction (HU ) 2.0, 4.0, 6.0) for a fixed solute-solute interaction (UU ) 4.0). As the head-solute interaction increases, the particles of condensed solute appear to become more elongated. The condensed solute particles in Figure 2a are nearly spherical and become increasingly prolate in parts b and c of Figure 2. This behavior can be rationalized by noting that the elongation of the solute particles increases the surface area and maximizes the number of favorable head-solute interactions. The solute in Figure 1a (system A) is not forming distinct clusters like those visible in Figure 2a (system A′), so it is difficult to determine whether the clusters are becoming more elongated with increasing head-solute interaction. The solute structures visible in parts b and c of Figure 1 are elongated, but since the head group of the surfactant is actually incorporated directly into the
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Figure 2. Final configurations for simulations including three-body interactions: (a), system A′; (b) system B′; (c) system C′; (d) system D′. The head sites are colored red, the tail sites are colored blue, and the solute particles are yellow. Four copies of the unit cell are dislayed for each configuration.
condensed solute, the amount of surface area of the solute particles is probably irrelevant. The tendency of the pure Lennard-Jones solute to form globular clusters relative to the solute with the threebody interaction is most likely a consequence of the higher numbers of nearest neighbors that are possible with the Lennard-Jones solute. The maximum number of nearest neighbors for the Lennard-Jones material is 12 while the maximum number for the three-body solute is 4. The Lennard-Jones solute can maximize the number of solutesolute interactions by forming a compact shape, and since a large number of these interactions is possible with the Lennard-Jones material, the solute condenses into a roughly spherical particle. For the three-body solute, the maximum number of solute-solute interactions is much smaller, so the solute-solute interactions may be competing with the more numerous, but weaker, solventsolvent interactions. This would allow for a more extended
and less compact particle. Experimentally, the behavior of the two different solutes may mimic systems where different coordination numbers are possible for the ceramic constituents. For example, aluminum ions in alumina can be either octahedrally or tetrahedrally coordinated. The higher coordination number may not be favorable for the formation of well-defined, ordered nanostructures. Using NMR techniques, Schmidt et al. found that most of the aluminum ions were tetrahedrally coordinated in the mesoporous materials they prepared.19 The systems with weak solute-head interactions also provide some interesting suggestions about the mechanism of solute nucleation and particle formation in the presence of surfactants. Parts a and d of Figure 2 clearly show that the solute particles are preferentially located (19) Schmidt, R.; Akporiaye, D.; Stooker, M.; Ellestad, O. H. J. Chem. Soc. Commun. 1994, 1493.
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Figure 3. Pair distribution functions, GHU(R), for the headsolute distance for systems A, B, C, and D.
Figure 5. Pair distribution functions, GUU(R), for the solutesolute distance for systems A, B, C, and D.
Figure 4. Pair distribution functions, GHU(R), for the headsolute distance for systems A′, B′, C′, and D′.
Figure 6. Pair distribution functions, GUU(R), for the solutesolute distance for systems A′, B′, C′, and D′.
in the regions where micelles are either in contact or nearly in contact. Although less pronounced, this also appears to be happening in Figure 1a where the highest concentrations of solutes are in the regions where micelles are nearly touching. Whether the clusters nucleate at these sites or whether they form elsewhere and then drift to the points of contact between micelles has not been determined. The possibility that the clusters nucleate at the contact points between micelles may be due either to preferential nucleation at the interface between two micelles or to a nonuniform distribution of ceramic material on the micelle surface. Additional insight into the behavior of these systems can be found by examining the pair distribution functions. The head-solute pair distributions for systems A-D are shown in Figure 3. The pair distribution functions for all systems were calculated during the last 50 000 steps of each simulation. The systems characterized by the weaker head-solute interactions, A and D, show a single nearest neighbor peak centered at R ) 1.7 and little additional structure. The systems with the strong head-solute interaction, B and C, show a much larger nearest neighbor peak as well as additional structure beginning at R ) 2.8. The extra structure in systems B and C is probably due to the aggregation of the solute, which does not appear to occur in systems A and D. The head-solute distribution functions for systems A′-D′, shown in Figure 4, exhibit similar behavior in the first neighbor peak, but all the distribution functions show additional secondary structure. As in the case of systems A-D, the height of the nearest neighbor peak tracks the strength of the headsolute interaction. The amount of secondary structure
appears to correspond closely with the amount of aggregation visible in Figure 2. The solute-solute pair distribution functions for systems A-D are shown in Figure 5. The aggregation of the solute is clearly visible in the large increase in secondary structure seen for systems B and C compared to systems A and D. There is a hint of aggregation apparent in the modest secondary peak in system A, but nothing like the large second, third, and fourth neighbor peaks visible in both systems B and C. The solute-solute distribution functions for systems A′-D′ are shown in Figure 6. All of the distribution functions show well-defined secondary structure, which agrees with the formation of distinct solute aggregates visible in each of the systems. The degree of secondary structure tracks the tendency of the solute to form spherical clusters. The systems showing the most secondary structure are A′ and B′, followed by system C′ and then D′. This is quite different from systems A-D, where the most secondary structure was exhibited by systems B and C, followed by systems A and D. However, in all cases the presence of secondary structure in the solute-solute distribution function appears to reflect the presence of solute aggregation. 4. Conclusions The inclusion of solute in these simulations, both with and without three-body interactions, shows that the presence of the solute can have a pronounced effect on the structure of micelles formed by a given surfactant. The simulations suggest that increasing the interaction between the solute and surfactant head group will disrupt spherical micelles and convert them to some other
Micelle Formation
structure, possibly a lamellar phase. This has important consequences for material synthesis, because the lamellar phase is usually the least desirable. A key factor in producing high-quality mesoporous ceramics is the control of the interaction strength between the surfactant head groups and the ceramic precursor. The differences in the structures of the condensed solutes for the systems with and without the three-body interactions indicate that the coordination number of the solute may play a role in the nucleation of the solute in the presence of surfactants. The simulations suggest that the lower coordinated solute nucleates more uniformly over the surface of the micelle, while the more highly coordinated solute nucleates exclusively at the points of contact between different micelles. However, no experimental studies on the role of coordination number in forming mesoporous ceramic materials have been performed at this time. The simulations also suggest that the initial clusters of solute particles tend to appear at the points of contact between different micelles. Whether this is due to clusters of solute preferentially nucleating at these points or whether the clusters are nucleating at random in the system and then moving to these points is difficult to determine at present. The fact that the clusters appear at the points where micelles contact each other may be an
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important factor in organizing the large scale structure of the micelles during synthesis. A large number of questions about these systems still remain. One area that will form the basis of future work is the issue of finite size effects. Although the simulations described here represent a substantial number of particles, they still remain too small to see what kinds of large scale structures will form, if given the chance. Because of the simplicity of the molecular model, it should be possible to achieve system sizes on the order of 50000-1000000 particles using advanced algorithms on parallel architecture computers. The larger aggregates sizes possible with these numbers of particles will make it possible to study what happens in the later stages of aggregate growth in these systems. Efforts in this direction are currently underway. Acknowledgment. This work was funded under the Laboratory Directed Research and Development program as part of Pacific Northwest National Laboratory’s Advanced Processing Technology Initiative. Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830. LA960562P
