Chemistry, synthesis, and characterization of functional polymers

Transcription

1 Chemistry, synthesis, and characterization of functional polymers Heikki Tenhu Laboratory of Polymer Chemistry University of Helsinki, Finland

2 Present research topics in the laboratory Controlled adical Polymerisation (ATP, Polyelectrolyte Complexes AFT) Stimuli esponsive Hydrogels Environmentally esponsive Polymers Nanocomposites Globules and Mesoglobules in Aqueous Media New Cellulose/Polysaccharide Gold/Silver/Copper Nanoparticles Derivatives Fluorinated Polymeric Surfactants New Waterborne Coating Formulations Self-organization of Block Copolymers Computer Simulation of Polymer Systems with Complex Topology Characterization of Structures and Intermolecular Interactions of Polymers with Complex Architectures Semiflexible liquid crystals, simulation by Dr. Anna Zarembo

3 Examples of aqueous responsive polymers: poly(nisopropylacrylamide) and poly(n-vinyl caprolactam) Virtanen, Janne: Self-Assembling of Thermally esponsive Block and Graft Copolymers in Aqueous Solutions Doctoral dissertation, University of Helsinki 2002 Laukkanen, Antti: Thermally responsive polymers based on N-vinylcaprolactam and an amphiphilic macromonomer, Doctoral dissertation, University of Helsinki 2005

4 Controlled radical polymerization Matyjaszewski, K. Prog. Polym. Sci. 30 (8-9) (2005)

5 Case 1: ATP (Satu Strandman, Anna Zarembo, Sami Hietala, Vladimir Aseyev) Synthesis of novel multifunctional initiators for star polymers Synthesis and characterisation of well-defined amphiphilic star block copolymers Self-assembling properties of the amphiphilic stars in aqueous solutions

6 Multifunctional ATP initiators H H Strandman, S. et al. J. Polym. Sci. Part A: Polym. Chem. 42 (2004) esorcinarene-based ATP Initiators for Star Polymers Strandman, S., Tenhu, H. Polymer 48 (2007) Star Polymers Synthesised with Flexible esorcinarene-derived ATP Initiators H H H H H H 1: 2: = H = CH 3 Type 1 Same number and structure of the initiating sites! Type 2 (with spacer) 3: = H 4: = CH 3

7 Synthesis of the amphiphilic stars MMA, DPE CuCl/2,2 -bipy 90 C tba, EC Cu/PMDETA 100 C (PMMA) 4 TFA CH 2 Cl 2 22 C (PMMA-b-ptBA) 4 (PMMA-b-PAA) 4

8 Saline solutions: CNTIN & Kratky representation on 4-armed stars (PMMA 73 -b-paa 143 ) 4 Strandman, S. et al. Polymer 47 (2006) Supramolecular Assemblies of Amphiphilic PMMA-b-PAA Stars in Aqueous Solutions mg/ml 4 wormlike chain 5 mg/ml h = 62 nm and 270 nm mg/ml 50 (qg) 2 P(q) 3 2 rod coil Debye-Bueche 1.25 mg/ml h (mean) = 111 nm Intensity mg/ml τ / μs 1 0 polydisp. rod hard sphere q g g = radius of gyration q = amplitude of the scattering vector = (4πn 0 /λ 0 )sin(θ/2) P(q) = particle scattering function = θ / θ=0

9 cryotem and modeling of 4-arm stars (PMMA 73 -b-paa 143 ) 4 no salt, ph M NaCl, ph nm no salt: simulation for block ratio 1:1

10 Sticky star mg/ml (collaboration with Katja Jankova mg/ml and Sören Hvilsted) G',G'' / Pa mg/ml 22 mg/ml 0,1 20 mg/ml 0,01 0,01 0, ω / rad/s Dynamic moduli of the polymer solutions in water at 20 C 10 G', G'' / Pa An image of a 42 g/l sample in water at 20 C Temperature / C Temperature dependence of the moduli of 26 mg/ml at 1 Hz oscillation frequency.

11 Case 2: AFT (Markus Nuopponen, Jun Shan, Katriina Kalliomäki et al.) Thermoresponsive block copolymers, polymer protected gold nanoparticles, stereo block polymers

12 Conventional vs Controlled adical Polymerization Short life-time apid polymerization Uncontrolled sidereactions Poor control over chain ends and molecular weights oad molecular weight distribution Extended life-time of growing chains No irreversible chain tranfer Narrow molecular mass distribution Accurate control over molecular mass and chain ends

13 AFT (eversible Addition Fragmentation Chain Transfer) Polymerization k P n * P - tr + m X P n -X + P m * k -tr k p monomer k p monomer S S CH 3 CH 3 S CH 3 S C S C C C 2 H CH S S H H2 2 CN CH 3 CH CH 3 cumyl dithiobenzoate 4-cyanopentanoicacid dithiobenzoate S,S -bis(a,a'-dimethyl-a''- acetic acid)-trithiocarbonate

14 AFT polymerization monomer A monomer B initiator Wide range of polymerizable monomers High molecular mass polymers Polymerizations in aqueous systems

15 Poly(N-isopropylacrylamide) - PNIPAM H 2 C C H N H C H C H 3 CH 3 N-isopropylacrylamide Thermoresponsive polymer Soluble in water below 32 ºC Phase separation above cloud point

16 Amphiphilic diblock copolymers with PNIPAM and hydrophobic blocks S S C H CH H 3 C C CH2 C C CH H n n H2 H2 2 CN N H Hydrophobic polystyrene CH(CH 3 ) 2 Hydrophilic PNIPAM Intensity b c a diameter / nm Size distributions of the aggregates at 20 C. a = PS48-PNIPAM346, b = PS75-PNIPAM118, c = P(t-BMA)135-PNIPAM123. Cryo-electron microscopy images of aggregates

17 Tacticity isotactic polymer atactic polymer Lutz et al Macromol apid Commun. 2004, 25, 486

18 A B A stereoblock polymers of NIPAM A-B-A stereoblock polymers with atactic PNIPAM as a hydrophilic block (either A or B) and a non water-soluble block consisting of isotactic PNIPAM were synthesized using AFT polymerizations. a-i-a atactic hydrophilic i-a-i isotactic water insoluble

19 A B A stereoblock polymers of PNIPAM When dispersed in water (low concentrations), the stereoblock polymers form, depending on the chain composition, branched micelle structures or spherical flower-like micelles. Stability and thermally induced collapse of micelles is strongly affected by block sequence 100 Turbidity i-a-i a-i-a Te mperature ( C) Turbidity of aqueous solutions of PNIPAM polymers. i2-a28-i2 ( ), i2-a40-i2 ( ), a12-i10-a12 ( ), a12-i5-a12( ) and a24.3 (line) measured by UV-vis spectrometry (c = 1.0 g L-1, heating rate = 0.2 C min-1).

20 Gold nanoparticles protected with AFT polymers ne-step synthesis of Au-PNIPAM-PMAA with a gold core, a PNIPAM inner shell and a PMAA corona. S C S PNIPAM-PMAA + HAuCl 4 LiB(C2H 5) 3H THF/methanol SS S S Au S S S SS PMAA blocks controll the colloidal stability of aggregates PNIPAM blocks showed an effect on the polarity of the immediate surrounding of the gold core

21 To conclude: Enormous progress in synthetic methods has taken place during the last ten years Controll over molar mass and its distribution, even over the stereostructure is possible by simple radical polymerization reactions Complex polymer structures Fine tuning of polymer structures will lead to a multitude of new applications, e.g. to new smart carriers of active substances