Di-Stimuli Responsive Diblock and Triblock Copolymer Particles

Transcription

1 Di-Stimuli Responsive Diblock and Triblock Copolymer Particles Nancy Weber, John Texter *, and Klaus Tauer Max Planck Institute for Colloids and Interfaces Department of Colloid Chemistry Golm, Germany * during sabbatical leave from Eastern Michigan University Ypsilanti, MI 48197, USA 1

2 What s Coming: block copolymer & particle synthesis not so common characterization technique: Ultrasonic Resonator Technology (URT) results for different PNIPAM block copolymers (such as PNIPAM, P1-PNIPAM, P1-PNIPAM-P2, PIL-PNIPAM, PIL-PNIPAM-PMMA) methods: URT, DLS, salt addition, FT-IR spectroscopy 2

3 bockcopolymer particles synthesis Ce 4+ NIPAM OH hydrophilic polymer OH aggregation of PNIPAM blocks (T>32 C) PSS - PNIPAM RT T > 32 C PNIPAM is hydrophobic at T > LCST, but contains still ca. 45 vol-% water and hence, it is quite a unique reaction space reactive particles (intermediates) sequental addition of monomers allows the synthesis of multi block copolymers and very special latex particles

4 4

5 Newton Laplace equation U 1 - compressibility - density 5

6 cell 1: water cell 2: sample DU = U 2 U 1 H 2 O sample sample volume: 200 µl 6

7 T < LCST sound wave not to scale diluted and more or less homogeneous solution 7

8 aggregation at T > LCST water is released and overall compressibility increases and hence, speed of sound decreases H 2 O H 2 O sound wave H 2 O H 2 O not to scale we are tracking hydration changes: the adhering layer of water molecules 8

9 U (m/s) sample H 2 O ,5 4,0 URT data evaluation sequence PSS PNIPAM block copolymer heating d U/dT (m/(s C)) 0,0-0,1-0,2-0,3-0,4-0, U (m/s) 3,5 3,0 2,5 2, LCST DU = U sample U water 9

10 d U/dT (m/(s C)) PNIPAM PEG-PNIPAM PSS-PNIPAM PDADMAC-PNIPAM double hydrophilic block copolymers (almost) no influence on LCST of PNIPAM 10

11 heating cooling hysteresis 34,0 33,5 33,0 32,5 32,0 31,5 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 c (wt-%) PEG-PNIPAM PDADMAC-PNIPAM PSS-PNIPAM PNIPAM PNIPAM PSS-PNIPAM PDADMAC-PNIPAM PEG-PNIPAM 300 mk / min (standard conditions) 11

12 concentration dependence of DLS data 10 5 PNIPAM 10 4 PEG-PNIPAM D i (nm) 10 3 PDADMAC-PNIPAM PSS-PNIPAM 10 2 T = 35 C ,01 0,1 1 c (wt-%) 12

13 hydrophilic - hydrophobic attachments to PNIPAM d U/dT (m/(s C)) 0,0-0,5-1,0-1,5-2,0 PEG(5k) - PNIPAM orig PNIPAM 1% PEG(5k) - PNIPAM - PS latex -2, increasing hydrophobicity 13

14 influence of the PEG chain length PEG - PNIPAM PEG - PNIPAM - PS 0,0 d U/dT (m/(s C)) -0,1-0,2-0,3-0,4-0,5 d U/dT (m/(s C)) 0,0-0,5-1,0-1,5-2,0-0,6-2, PEG g/mol PEG 10 6 g/mol 14

15 a case study PIL - PNIPAM two block copolymers hydrophobic effect of alkyl chains? PDADMAC - PNIPAM PEL behavior (double hydrophilic polymer) poly(1 - (11 - acryloyloxyundecyl) 3 methylimidazolium bromide (PIL)

16 0,1 d U/dT (m/(s C)) 0,0-0,1-0,2-0,3-0,4 PS latex sulfoniert sulfonated PDADMAC-PNIPAM PIL - PNIPAM -0,

17 D i (nm) PIL - PNIPAM PDADMAC - PNIPAM PS latex sulfonated URT and DLS reveal clear difference between PIL PNIPAM and PDADMAC - PNIPAM 17

18 Heating cooling cycle (PIL PNIPAM) a initial condensation as solution warms; b the whole solution has warmed; c the suspension is actively boiling; d the suspension is being cooled in ice; e clear solution after re-dissolution of poly(nipam) cores following cooling in (d).

19 PIL - PNIPAM increasing ionic strength (KBr, NaBF 4 addition) changing the solution state 19

20 KBr addition/removal cycle a starting 1.9% (w/w) solution of PIL b just noticeable turbidity at abut 0.4 M KBr and hard foam due to diblock becoming essentially a nonionic surfactant due to high bormide binding; c highly turbid condensation product at 2.56 M KBr; d same as in (c) but in smaller culture tube; e after extensive dialysis (18 h) to remove excess KBr

21 KBr addition KBr temperature 10 4 PIL - PNIPAM / 23 C 10 3 D i (nm) ,0 0,5 1,0 1,5 2,0 C KBr (M) PIL - PNIPAM NaBF4 KBr particles size evolution of poly(ilbr-b-nipam) solution upon stepwise addition of 4.64 M aqueous KBr solution rather unexpected result (PNIPAM is turned off) also no URT response 21

22 PNIPAM behaves differently in PIL copolymers than in other block copolymers with PDADMAC, PSS, or PEG? 22

23 complex formation between PIL and PNIPAM 0,02 PIL + PNIPAM: components and physical mixture d U (m/(s C)) 0,00-0,02-0,04-0,06 D i (nm) ,08-0, PIL-2 PNIPAM PNIPAM+PIL-2 physical mixture of 1:1 by weight 23

24 PIL + PNIPAM: physical mixture equal masses d U (m/(s C)) -0,02-0,03-0,04-0,05-0,06-0, D i (nm) -0, formation of a complex between PIL and PNIPAM physical mixture of 1:1 by weight 24

25 R n n NIPAM n IL 0,00-0,02 R n =0.125 R n =1 d U (m/(s C) -0,04-0,06 R n =7 R n =13-0,08 c = 0.4 wt-% all mixtures are solutions (no visible turbidity)

26 complex formation between PNIPAM and PIL monomers and polymers O O CH 2 CH 2 N Br N CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 transmission transmission (2) (1) wavenumber (cm -1 ) amide band wavenumber (cm -1 ) imidazolium ring CH 2 CH C NH O C CH 3 CH 3 H PIL 1 PNIPAM+PIL1 PNIPAM b PIL - PNIPAM (NW23A) 26

27 blockcopolymer particles synthesis due to complex formation: change of properties of the reactive intermediate if hydrophilic precursor polymer is replaced by PIL ionic-like interior causes difficulties to incorporate nonpolar or hydrophobic monomers styrene almost no polymerization MMA performs a little better

28 PIL PNIPAM precursor copolymers D i (nm) PNIPAM d U/dT (m/(s C)) D i (nm) d U/dT (m/s C)) PIL - PNIPAM (NW18A) PIL - PNIPAM (NW23A)

29 PIL PNIPAM PMMA triblock copolymers precursor diblocks d U/dT (m/(s C)) D i (nm) d U/dT (m/(s C)) PIL - PNIPAM - PMMA (NW18B) PIL - PNIPAM - PMMA (NW23B) PIL - PNIPAM - PMMA (NW18B) PIL - PNIPAM - PMMA (NW23B)

30 explanation during cooling: the solubility of the PNIPAM block increases and pulls the presumably quite short PMMA into the water during heating: the whole precipitation occurs stepwise: 1. PMMA block causes aggregation as recorded by DLS at lower temperature 2. at higher temperature the hydration water is released as recorded by URT 30

31 Nancy Weber John Texter

32 Summary PIL PNIPAM diblock copolymers show responsiveness against temperature and salt PIL PNIPAM PMMA triblock copolymers show a transition temperature below room temperature URT is a powerful tool to study phase transitions and a complementary method to established techniques complex formation between imidazolium compounds and NIPAM determines the scene Thank You 32