Chemical and Biological UB

Transcription

1 Buffalo, New York

2 Chemical and Biological UB AlexandridhV AndreadhV KoffaV TzanakakhV Tsianou MountziarhV KalogerakhV TsamopouloV tissue engineering metabolic engineering stem cell biotechnology molecularly engineered materials

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4 air VOC reduction biomolecular structure & interactions water & ground environment health delivery carriers scaffolds Green chemistry benign processing ChemE s critical save the issues world! diagnostics surface modification energy clean energy catalysis, photovoltaics energy storage batteries, capacitors energy conservation efficient manufacturing

5 solvents self/directed assembly polymers particles Alexandridis lab

6 Self-Assembly National Research Council: Beyond the Molecular Frontier, NAP, Grand Challenge for Chemists and Chemical Engineers: Develop self-assembly as a useful approach to the synthesis and manufacturing of complex systems and materials. Mixtures of properly designed chemical components can organize themselves into complex assemblies with structures from the nanoscale to the mesoscale, in a fashion similar to biological self-assembly. SCIENCE VOL JULY 2005 PG 95

7 solvents self/directed assembly polymers particles

8 aqueous solvents interactions with organics formulations pharmaceutics, consumer products solubilization & dispersion benign synthesis of nanomaterials environment solvents self/directed assembly health biopolymers in solution, on surfaces drug delivery carriers, dissolution polymers particles alternative solvents reactions, separations Alexandridis energy lab nanomanufacturing hybrid materials electrolytes polymers, nanoparticles

9 SCM-EMP, October 22, 2010 Self-Assembly of Amphiphilic Block Copolymers Fundamentals and Applications PascalhV AlexandridhV Department of Chemical and Biological Engineering University at Buffalo The State University of New York Buffalo, NY Acknowledgements: NSF, NIH, NCNR-NIST, Dow Chemical, Kao Corp.

10 Outline self-assembly < > bio/nanotechnology bottom-up manufacturing: nm-micron length-scales molecular engineering block copolymer self-assembly fundamentals novelty - opportunities & challenges thermodynamics & structure intermolecular forces applications in formulations solvents as degrees of freedom and processing aids structure-property relationships applications in nanoparticle synthesis domains for metal nanoparticle synthesis and stabilization nanoreactors for semiconductor nanoparticle synthesis

11 Self-Assembly of Surfactants surfactant number N s v la o head tail v: volume of the hydrophobic portion of the surfactant molecule l: length of the hydrocarbon chain a o : effective area per head group Sphere N s =0.33 Cylinder N s =0.50 Planar bilayers N s =1 Vesicles Inverted N s 1 sphere N s 1

12 Polymers homopolymer random copolymer micro-phase separation: organization in the nanoscale block copolymer

13 Self-Assembly of Block Copolymers ordered morphologies formed by self-assembly of block copolymers (one-component system) depend on volume fraction of the blocks of the copolymer and on degree of segregation (χn) domain size (~10 nm) related to polymer chain dimensions a given block copolymer would attain a single ordered morphology above the order-disorder transition

14 A-B Block Copolymer + A_Solvent + B_Solvent isothermal structural polymorphism of PEO-PPO block copolymer in the presence of two immiscible solvents selective for each block Alexandridis, P.; Olsson, U.; Lindman, B. Macromolecules 1995, 28, Alexandridis, P.; Olsson, U.; Lindman, B. J. Phys. Chem. 1996, 100, Alexandridis, P.; Olsson, U.; Lindman, B. Langmuir 1997, 13, Alexandridis, P.; Olsson, U.; Lindman, B. Langmuir 1998, 14, Svensson, B.; Alexandridis, P.; Olsson, U. J. Phys. Chem. B. 1998, 102,

15 Amphiphilic Block Copolymers in Selective Solvents Opportunities (almost) everything you can do with dry block copolymers (almost) everything you can do with surfactants added degrees of freedom in product/process design expanded phase space extended structural length-scales higher loading capacity (actives, particles) local environment (gradient properties; partitioning; reactivity) higher mobility (faster equilibration; easier processing) structural transitions (faster trigger) self-healing (around thermodynamic equilibrium state) biomimetic (help connect synthetic to natural: cells, ECM) several industrial applications involving solvents Challenges need to establish the fundamentals (too) many interactions to control/modulate lack of robustness (more delicate systems) thermal stability mechanical properties polymer solvent

16 Self-Assembly of Amphiphilic Polymers: Fundamentals Micelles in solution and ordered (lyotropic liquid crystals) phase behavior and structure thermodynamic origin of self-assembly degree of block segregation intermolecular and inter-micellar interactions dynamics: polymer and solvent mobility solvent location and self-assembled structure solution/material properties affected by self-assembly surface organization and interfacial interactions Practical considerations thermodynamic vs. kinetic stability processing and structure multicomponent systems natural polymers & surfactants health and environment cost (do more with less) micelle formation, shape, dimensions, and composition tuned by solvents & solutes

17 Model Amphiphilic Block Copolymers: Poloxamers Poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers MW = 2000 to (SDS has 12 bonds, Pluronic F127 about 800) PEO is very flexible; whereas Pluronics are triblock copolymers, they can be considered as diblocks for many purposes (cut the triblock in the middle) Segregation between PEO and PPO not strong (PPO retains polar character) LCST: PEO well-known to phase separate from water at high temperatures; the same happens for PPO but at lower temperatures PEO is crystalline up to oc but melts at lower T if some water is present Nonionic Commercially available as Poloxamers or Pluronics in a range of MWs and compositions

18 Block Copolymer + Selective Solvent = (Nano) Structure PEO-PPO block copolymer (P105) temperature-composition phase behavior in the presence of water (selective solvent for PEO) Alexandridis, P.; Zhou, D.; Khan, A. Langmuir 1996, 12, Alexandridis, P. Macromolecules 1998, 31, I 1 micellar cubic H 1 hexagonal V bicon. cubic Lα lamellar Ordered structures formed by diblock A-B copolymers of varying block compositions (in the absence of solvent)

19 Thermodynamics of Ordered Solvated Block Copolymers self-consistent mean-field modeling Predicted phase diagram Segment vol. fractions MW Scaling of spacing Experimental data (motivation) Svensson, M.; Alexandridis, P.; Linse, P. Macromolecules 1999, 32,

20 Lattice parameter, d (A) Log 10 Pressure (Pa) Log Pressure (Pa) Intermolecular and Inter-assembly Interactions 9 Osmotic pressure of Pluronic P105 gel Cryo-TEM micrograph of 1 wt % aqueous EO126- B45 solution. Zheng, Y.; Won, Y.-Y.; Bates, F. S.; Davis, H. T.; Scriven, L. E.; Talmon, Y. J. Phys. Chem. B. 1999, 103, l h =0.5 A 5 4 L 3 1 I 1 H 1 L a H P105 wt% l =1.1 A h P105 H O/EO= l =16.6 A p F127 H 2 O/EO=1.3 l p =11.5 A F Lattice parameters of Pluronic block copolymer gels 6.5 P F Lattice separation, d w or d h (A) 120 P Block copolymer (wt%) Osmotic stress is used to measure intermolecular forces in ordered assemblies formed by hydrated PEO-PPO block copolymers The 16.6 Ǻ (11.5 Ǻ) decay length is comparable to the radius of gyration of the PEO block Gu, Z.; Alexandridis, P. Macromolecules 2004, 37,

21 Self-Assembly of Amphiphilic Polymers: Applications intramolecular & supramolecular local environment compartments long-range order amphiphilic polymer solvent formulations metal nanoparticles semiconductor nanomaterials Lin YANG Unilever E. ANTONIOU TU-Crete Yining LIN Kazuhiro KAIZU Kao Corp.

22 Principle: Structure Solvent Structure 1. Phase behavior Solvent location 2. Lattice parameter 3. Interfacial area Solvent effects Solvent properties Solubility parameter : Octanol / water partition coefficient : δ LogP

23 Solvent Location and Lattice Parameters d (Lattice parameter) ~ a p (Interfacial area per one PEO block) 1 Φ int (Volume of interfacial region) 5 0 Glycerol Glycerol -5 p-xylene p-xylene -10 Triacetin Triacetin -15 Propylene carbonate Cosolvent (vol%) / (Cosolvent + Water) (Vol%) Propylene carbonate Alexandridis, P.; Ivanova, R.; Lindman, B. Langmuir 2000, 16(8), Holmqvist, P.; Alexandridis, P.; Lindman, B. Langmuir 1997, 13(9),

24 Solvent Effects on Phase Behavior and Structure Phase behavior P105 P105 P105 P105 Lα Lα Lα Lα V2 V1 I1 H1 I1 H1 L I1 H1 V1 L2 I1 H1 H2 I2 L2 L1 L1 L1 Water Glycerol Water Propylene carbonate Water Triacetin Water p-xylene Solvent location With decreasing solvent polarity, the solvent location changes from water-rich domains, to PEO-PPO interface, to PPO-rich domains Kaizu, K.; Alexandridis, P., unpublished data.

25 Shear-induced Alignment and Orientation Transitions low-block copolymer content lamellar phases Lα Lα nm mm Zipfel, J.; Berghausen, J.; Schmidt, G.; Lindner, P.; Alexandridis, P.; Richtering, W. Macromolecules 2002, 35,

26 Solution Structure & Properties Tuned by Solvents In Progress: Structuring in Ionic Liquids nanostructure of ionic liquids ionic liquids & molecular solvents (interactions) nanostructure in ionic liquids (self-assembly) applications of structured ionic liquid media Smart Formulations US Patent 6,503,955: Pourable liquid vehicles dilution liquid gel Ivanova, R.; Lindman, B.; Alexandridis, P. Langmuir 2000, 16, Ivanova, R.; Lindman, B.; Alexandridis, P. J. Colloid Interface Sci. 2002, 252,

27 Self-Assembly of Amphiphilic Block Copolymers Fundamentals and Applications in Formulations thermodynamic origin of self-assembly phase behavior and structure mean-field modeling intermolecular and inter-micellar interactions degree of block segregation dynamics: polymer and solvent mobility location of solvent and self-assembled structure solution/material properties affected by self-assembly processing and structure

28 Self-Assembly of Amphiphilic Polymers: Applications intramolecular & supramolecular local environment compartments long-range order amphiphilic polymer solvent formulations metal nanoparticles semiconductor nanomaterials Toshio SAKAI Shinsyu University

29 Single-step synthesis of gold nanoparticles using PEO-PPO block copolymers Mixing of aqueous metal salt solution and aqueous solution of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer (Pluronic or Poloxamer) at ambient conditions Metal salt HAuCl 4 Pluronic P mm 5.0 mm (0.2 ml) (2 ml) 0 min 5 min 10 min 20 min 60 min 120 min Solvent: Water Sakai, T.; Alexandridis, P. Langmuir 2004, 20, Preparation of Metallic Nanoparticles, US Patent 7,718,094.

30 Unique features of PEO-PPO block copolymer media for metal nanoparticle synthesis PEO-PPO block copolymers act in tandem as reductants, colloidal stabilizers, and morphogenic agents Much more effective than homopolymer PEO or PPO Minimum number of components: metal salt, block copolymer (reductant/stabilizer) and solvent Single-step operation: simple mixing of aqueous metal salt solution and aqueous PEO-PPO block copolymer solution Ambient reaction conditions: room temp. and air-saturated water No external energy input required Environmentally benign materials and conditions Commercially available polymers (Pluronic or Poloxamer) Possibility of using various types of PEO-PPO block copolymers (MW, PEO/PPO ratio, architecture, block sequence, CMC) PEO-PPO block copolymers self-assemble in solution and on surfaces

31 Relationship between particle size and reaction mechanism Metal ion reduction and the resulting size/shape of metal colloids can be controlled by the amphiphilic character of PEO-PPO block copolymers (PEO-promoted reduction and PPO-promoted adsorption on particles) Longer polymer Longer PEO blocks Nucleation (AuCl 4 - reduction in the bulk solution) Smaller particles Higher PPO content Heating Less polar solvent Longer polymer Higher PPO content Polymer adsorption on seed Complexation of AuCl 4 - with polymers Complexation of AuCl 4 - with polymers AuCl 4 - reduction to form Au 0 AuCl 4 - reduction on surface Seed formation Growth (AuCl 4 - reduction on the particle surface) Particle formation Stabilization (AuCl 4 - reduction completion and stabilization) Larger particles Individual particles Aggregates Networks Growth Stabilization/no growth Sakai, T.; Alexandridis, P. J. Phys. Chem. B 2005, 109(16),

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33 Are lyotropic liquid crystal (LLC) structures required for shape control of metal colloids? Au colloid synthesis using: EO 100 PO 65 EO 100 (Pluronic F127) Higher metal ion reduction activity Micellar solution and heat-induced micellar cubic LLC EO 13 PO 30 EO 13 (Pluronic L64) Lower metal ion reduction activity Micellar solution, hexagonal and lamellar LLC Au colloid synthesis in various phases, conc. and temperature 3D ordering of Au colloids in LLC media Plates remain well dispersed in hexagonal and lamellar LLC Polyhedral particles well dispersed in micellar cubic LLC Thermoreversible formation of micellar cubic LLC containing Au colloids 600 nm 6 μm Lamellar LLC (70 wt% L64) Micellar cubic LLC (20 wt% F127) Normal light Polarized light at ~4 C at ~50 C

34 Self-Assembly of Amphiphilic Polymers: Applications intramolecular & supramolecular local environment compartments long-range order amphiphilic polymer solvent formulations metal nanoparticles semiconductor nanomaterials G. N. KARANIKOLOS NCSR Demokritos T. J. MOUNTZIARIS U-Mass Amherst

35 Reverse Micelles as Reactors for Nanoparticle Synthesis synthesis of compound semiconductor (ZnSe) nanocrystals (quantum dots) size-dependent luminescence broad excitation narrow and symmetric emission high brightness & sensitivity high extinction coefficients photochemical stability Amphiphile (PEO-PPO block copolymer) 5 nm HR-TEM images of ZnSe nanocrystals ~6 nm diameter formed by reacting 0.3 M diethyl-zinc solution in 40 nm heptane droplets with H 2 Se gas. DEZn in Heptane Diffusion Polar Phase (Formamide) H 2 Se in H 2 Gas Bubble H 2 Se in H 2 Karanikolos, G. N.; Alexandridis, P.; Itskos, G.; Petrou, A.; Mountziaris, T. J. Langmuir 2004, 20,

36 Block Copolymer Templates for Nanoparticle Growth Hexagonal (H 1 ): Cylindrical nanodomains Micellar Cubic (I 1 ): Spherical nanodomains under polarized light: H 1 I 1 2-phase Micellar (L 1 ): Spherical nanodroplets Two-Phase Region

37 Stable Liquid Crystal Templates for Nanowire Synthesis Karanikolos, G. N.; Alexandridis, P.; Petrou, A.; Mountziaris, T. J. Nanotechnology 2005, 16 (10), nm Stable Liquid Crystal Templates for Nanoplate Synthesis Xylene + PPO less polar domain Water/Zinc Acetate + PEO polar domain Xylene + PPO less polar domain 10 nm Lamellar Liquid Crystal Exposure to H 2 Se ZnSe thin layer formation Karanikolos, G. N.; Petrou, A.; Alexandridis, P.; Mountziaris, T. J. Nanotechnology 2006, 17,

38 Templated Growth Mechanism Local block copolymer structure without and with incorporation of nanoparticles at high density: (a) parent block copolymer (b) parent block copolymer selectively swollen with smaller nanoparticles at high density; the diameter of the particles is much smaller than the radius of gyration of the polymer leading to a homogeneous particle distribution with little effect on chain conformations (c) parent block copolymer selectively swollen with larger nanoparticles; the diameter of the particles is of the order of the radius of gyration of the chains, thus leading to significant perturbations of the block chain conformations which are energetically unfavorable (d) at high particle fractions in order to lower the chain conformational entropy the larger particles segregate into a central core In Progress: Nanoparticles in ABCs nanoparticles & polymer chains (interactions) nanoparticle effect on phase behavior & structure applications of ABC-nanoparticle hybrids

39 Self-Assembly of Amphiphilic Block Copolymers Applications in Nanomaterials Synthesis one-pot and one-step synthesis of metal nanoparticles PEO-PPO block copolymers as reducing, stabilizing and morphogenic agents interplay between polymer localization and metal ion reduction activity organized particle - polymer composites self-assembled domains as nanoreactors interplay between matrix dynamics and reaction kinetics self-assembled templates for semiconductor nanostructures interplay between polymer chains and growing nanoparticles 10 nm

40 Thank you!

41 aqueous solvents interactions with organics Alexandridis lab formulations pharmaceutics, consumer products solubilization & dispersion benign synthesis of nanomaterials environment solvents self/directed assembly health R biopolymers in solution, on surfaces drug delivery carriers, dissolution polymers particles energy alternative solvents reactions, separations electrolytes polymers, nanoparticles nanomanufacturing hybrid materials

42 Solvated Block Copolymers: Degree of Block Segregation The selective solvent swells the blocks of a given type and enhances their segregation from the block of other type. Evidence for intermediate-to-weak block segregation: (i) chemical nature of PEO and PPO (ii) random-coil-like scaling of lattice spacing with polymer MW (iii) segment volume fraction profiles predicted from mean-field theory (iv) ability to form many different phases at the same temperature by varying the solvent ratio (v) (vi) stability of bicontinuous cubic structures reduction in the number and stability of ordered phases upon decrease of the polymer MW in ternary isothermal systems, reminiscent of the order-disorder transition observed in neat block copolymers upon a decrease in c N

43 Lattice Mean-Field Theory for Self-Assembly Prediction Assumptions space divided into lattice cells of equal size flexible polymers mean-field approximation in two dimensions nearest neighbor interactions through c-parameters Capabilities multicomponent systems multiblock copolymers multibranched polymer architecture computational efficiency Helmholtz free energy for multicomponent system * * ( A - A ) ( A - A ) - ln ( U -U int int * Internal energy arising from internal states A int i A n Ai Mixing entropy ln - nxc ln * x c B P ABi U n r xc xc x AB Interaction energy 1 M U L f P i Ai 2 i A A B B ' ' P ln g ABi c BB' ABi AB P A' B' i f A' i U f c P n * Ai ABi xc AB xc ) BB', g AB internal energy and degeneration of the state species volume fraction nearest neighbors interaction parameter fraction of species A in state B number of chains of component x in conformation c degeneration of a conformation c of component x The quantities marked with asterisk correspond to the reference pure amorphous system

44 Micelle Dimensions and Composition Tuned by Solvent micelle association no. micelle core radius micelle radius SANS experiments under conditions of variable solvent contrast indicate that ethanol partitions in the micelle while glycerol partitions in the aqueous phase Alexandridis, P.; Yang, L. Macromolecules 2000, 33,

45 Drying and Swelling of Lyotropic Liquid Crystals Equilibrium properties Ordered structures may affect transport properties Transport properties Self-assembled or ordered structure e.g., intermolecular interactions, water activity, scaling laws, etc. Transport properties (kinetics) may also affect ordered structure e.g., drying or swelling of polymers, polymer dissolution, etc. Diffusion in Matrix vs. Evaporation from Surface Self-Assembled Structure vs. Hydration Level x Water vapor (RH) Water vapor Water vapor h(t) t = 0 t = t_intermediate t = t_final time Gu & Alexandridis, Langmuir 2005, 21, 1454.

46 Drying rate (g/m 2.hour) Drying rate (g/m 2.hour) Drying: Self-Assembled Structure vs. Hydration L64 P105 F127 PEG4000 PEG L64 P105 F127 PEG4000 PEG PEO content % RH 2 85% RH Water content (wt%) Corrected water content (wt%) Drying rate decreases when PEO content of the copolymer increases interactions between PEO and water stronger. PEO content: L64 (40%) < P105 (50%) < F127 (70%) < PEG4000 = PEG20000 When the drying rate is plotted against corrected water content based on PEO, the drying rates for different polymers overlap, indicating that hydration level, rather than the ordered structure, affects primarily the drying rate. Gu & Alexandridis, Langmuir 2005, 21, 1454.

47 Relative viscosity 8wt% P105 40wt% glucose Solution Viscosity wt% P105 40wt% glucose Micelle Shape & Volume Plain water 40 wt% glucose in water 1 8wt% P105 1wt% P105 1wt% P105 1wt% P Temperature ( C) Solution viscosity increase upon addition of glucose Kaizu, K.; Alexandridis, P. unpublished data. 60 C coincides with micelle shape change from sphere to ellipsoid and is attributed to the dehydrating effect of glucose on the micelle corona 55 C 8wt% P105 shape change interactions 8wt% P105

48 Amphiphilic Polymers for Metal Nanoparticle Synthesis PEO-PPO copolymers act in tandem as reducing, stabilizing and morphogenic agents PEO-PPO block copolymers Metal ions Metal ion reduction Metal colloid formation Size/shape control Colloidal stabilization Spherical Ag nanoparticles in PO 19 EO 33 PO 19 formamide solutions at ~100 C Ag nanonetworks in EO 37 PO 58 EO 37 formamide solutions at ~100 C Sakai, T.; Alexandridis, P. Chem. Mat. 2006, 18(10), Spherical Au nanoparticles in EO 37 PO 58 EO 37 aqueous solutions at ~25 C 100 nm 100 nm Polyhedral Au particles in EO 37 PO 58 EO 37 formamide solutions at ~100 C Au nanoparticles remain dispersed for a year in 5 mm EO 37 PO 58 EO 37 aqueous solutions at ~25 C Sakai, T.; Alexandridis, P. Langmuir 2005, 21(17), nm 100 nm Au plates in EO 37 PO 58 EO 37 aqueous solutions at ~25 C Sakai, T.; Alexandridis, P. Nanotechnology 2005, 16(7), S344-S353. {111} {100} {111}