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Introduction to Macromolecules CHM5080 (CUHK) – CHEM588 (HKUST) – CHEM6108 (HKU)

Introduction to Macromolecules CHM5080 (CUHK) – CHEM588 (HKUST) – CHEM6108 (HKU). Lecturers: Chi WU (CUHK) chiwu@cuhk.edu.hk Ben Zhong TANG (HKUST) tangbenz@ust.hk Wai Kin CHAN (HKU) waichan@hkucc.hku.hk.

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Introduction to Macromolecules CHM5080 (CUHK) – CHEM588 (HKUST) – CHEM6108 (HKU)

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  1. Introduction to Macromolecules CHM5080 (CUHK) – CHEM588 (HKUST) – CHEM6108 (HKU) Lecturers:Chi WU (CUHK) chiwu@cuhk.edu.hk Ben Zhong TANG (HKUST) tangbenz@ust.hk Wai Kin CHAN (HKU) waichan@hkucc.hku.hk TA: Ms Shi Feng, Room 226C, 2609-6266, fengshi@cuhk.edu.hk Time/date:CUHK: L1 & L2 Science CentreFeb 10 & March 3 10:00-12:30 HKUST: Rm 2405 (Academic Building) March 17 & 31 14:00-17:30 HKU: P3, Chong Yuet Ming Physics Building April 14 & 28 Final Exam: CUHK/HKUST/HKU May 12,10:00-12:30 (Saturday) Textbooks: “Introduction to Polymers”, 2nd edition By R. J. Young and P. A. Lovell, 1991, Chapman & Hall, QD381.Y68 “Introduction to Macromolecular Science” By Petr Munk, 1989, John Wiley & Sons, QD381.M85

  2. CUHK 1. Concept of macromolecules 2. Structures of macromolecules 3. Characterization of macromolecules HKUST 4. Classification of polymerization reactions 5. Step (or condensation)polymerization 6. Chain (or addition) polymerization 7. Copolymerization HKU 8. Ionic polymerization 9. Coordination polymerization 10. Controlled radical polymerization 11. Synthesis of polymers with special properties Outlines

  3. Natural Macromolecules Proteins, DNA, RNA Polysaccharides (cellulose: plants & animals) Synthetic Macromolecules Polystyrene, polyethylene Poly(vinyl chloride) Polyesters, polyurethane, ... Oligomers (M > 104 g/mol) Small molecules Macromolecules * Homogeneous * No swelling in dissolution * Purification methods * Low viscosity * Simple structures * Inhomogeneous (size & mass) * Swelling in dissolution * Precipitation, GPC, … * High viscosity * Complicate structures. The Basics of Macromolecules The difference between small molecules and macromolecules

  4. * Primary structures Composition:number & types of atoms Configuration:how they are connected Homopolymer & heteropolymers: linear, branching, star, grafting, ladder, ... block, seqential, graft, random, ... * Secondary structures Comformation: folding, helix, sheet, ... * Tertiary structures Special arrangements of larger segments (helix & sheet) to form a complicate structure Spatial multi-chain aggregates, intra- and inter-chain interaction, e.g., triplethelix and enzyme * Quaternary structures Structures of macromolecules

  5. * Backbone contains only carbon atoms Polyethylene Low (H.P.) and high (L.P.) density PE - Polymeric hydrocarbons: Polypropylene isotactic, syndiotactic & atactic Polybutadiene 1,2 addition and 1,4 addition (cis & trans) Polyisoprene -(CH2C(CH3)=CHCH2)n- natural rubber Polystyrene The most representative polymer - Halogen-containing: Poly(vinyl chloride) -(CH2CCl)n- common polymer Polytetrafluoroethylene Teflon, The king of plastic Primary structures Polytrifluorochloroethylene Tough and inert - With polar side groups: Poly(methyl methacrylate) Organic glass Poly(hydroxyethyl methacrylate) Gel contains 35% water Polyacrylamide Typical water soluble polymer Polyacrylic acid Washing power, useful polymers Poly(vinyl alcohol), Poly(vinyl pyrrolidone), …. - Polymers with heteroatoms in the backbone: Polyether - PEO; Polyesters -(O-(CH2)a-CO)n-, PCL; Polycarbonates -(O-R-O-CO)n-; Polyamides -(NH-(CH2)a-CO)n-; Polyurethanes -(NH-R1-NH-CO-O-R2-O)n-; Polyureas; ...

  6. (1-10 x 1013 cells) base Replication DNA P sugar DNA sugar sugar RNA Thymine Uracil DNA / RNA H OH 3 basic ones H 2 acidic ones Proteins H2N-C-COOH 5 polar ones R 10 non-polar ones regulatory sequences Genomes Genes DNA chains Segments exon (~1.5%) intron (~25%) Natural macromolecules: DNA, RNA, Proteins, Polysaccharides … infinitely different outside The living organisms (1-10 x 107) fundamentally similar inside Heredity four nucleotides Procaryotes + eucaryotes Adenine Thymine Guanine Cytosine purines pyrimidines Transcription Translation catalytic function ~30%

  7. Polysaccharides: Physical Forms and Variables Variables Monosaccharide substituents Glycosidic linkages Molecular size profile Substitution patterns Cross-linking Physical forms Powders Solutions Hydrogels Hydrocolloids Fibres Films

  8. 4)-b-D-Glcp-(14)-b-D-Glcp-(1 Cellulose Principal constituent of plant cell walls. Wood & Cotton are the major industrial sources

  9. amylose amylopectin 4)-a-D-Glcp-(14)-a-D-Glcp-(1 Starch ( Amylose & Amylopectin ) Major industrial sources of starch are wheat, maize (yellow maize & waxy maize starches), potato, rice, tapioca and sago. The ratio of amylose to amylopectin is characteristic of botanical origin.

  10. * Primary structures Composition:number & typs of atoms Configuration:how they are connected Homopolymer & heteropolymers: linear, branching, star, grafting, laddle, ... block, seqential, graft, random, ... * Secondary structures Conformation: folding, helix, sheet, ... * Tertiary structures Special arrangements of larger segments to form a complicate structure, e.g., helix Spatial multi-chain aggregates, intra- and inter-chain interaction, e.g., triplethelix and enzyme * Quaternary structures Structures of macromolecules

  11. Structure of a protein chain: Primary: Secondary and Tertiary Structures

  12. Stickers move randomly like a “gas” Stickers move in a more correlated fashion like a “liquid” Stickers are restricted like a “solid” *. Helical structure - Proteins, amylose and nucleic acids Energy vs Entropy Random coil vs Ordered conformation It requires two hydrogen bonds in the formation of the helix (not proline). It contains 3.6 amino acid residues per turn; subsequent residues are rotated 100owith a pitch of 5.4 A; and the translation is 1.5 A per residue. *. Chain folding of some regulated heteropolymer chains Secondary structures - Conformation

  13. T < ~32 oC T increases dcreases PNIPAM-g-PEO 80 1.8 pyrene: an imitated drug 60 1.6 I1/I3 T / oC 40 1.4 20 1.2 0 0 10 20 30 40 50 t / min A single polymer chain core-shell nanostructure Chi Wu, Xingping Qiu, Physical Review Letters, 79, 620 (1998); Macromolecules, 30, 7921 Secondary structures Applications One of the envisioned applications is the smart temperature-sensitive drug delivery device. Protein denaturation Heat denatured & chemical denatured

  14. * Primary structures Composition:number & typs of atoms Configuration:how they are connected Homopolymer & heteropolymers: linear, branching, star, grafting, laddle, ... block, seqential, graft, random, ... * Secondary structures Conformation: folding, helix, sheet, ... * Tertiary structures Special arrangements of larger segments to form a complicate structure, e.g., helix Spatial multi-chain aggregates, intra- and inter-chain interaction, e.g., triplethelix and enzyme * Quaternary structures Structures of macromolecules

  15. Secondary structure - helix Heat Chemical Tertiary structures - Arrangement of larger segments Particular spatial arrangement Enzymatic Catalysis Energy - adenosine triphosphate (ATP) Specific & fast Chymotrypsin - a “hydrophobic pocket - aromatic amino acids Trypsin - an ionized carboxyl - interacted with the basic groups

  16. A zig-zag chain A thread chain A random coil -b b o Step motion: D Rn = b or -b Let us start with a polymer chain in one dimensional space. It has N segments and each segment has a length of b. A random walk After N steps and if n steps are positive, R = bn + (-b)(N-n) = b(2n-N) The chance (probability) to find n positive steps is a binomial distribution because Pn is related to (p + q)N when p = q = 1/2. The mean value of n can be calculated as <R> = 0

  17. Hydrodynamic Radius (Rh) End-to-End Distant R = rN - ro In a good solvent, a chain is in the random coil state. Radius of gyration

  18. N ~ 102-1010 in poor solvent N ~ 102-1010 in theta solvent N ~ 102-1010; A rigid chain N ~ 102-1010 in good solvent Earth Moon Polymer size: Polymer size depends on solvent quality Let us imagine an increase in monomer size from 0.1 nm to 1 cm. R = bN1/3~ 5 cm - 50 m R = bN1/2 ~ 10 cm -1 km R = bN3/5~ 16 cm– 40 km R = bN~ 100 cm- 105 km

  19. Thin rod:Rg2 = L2/12 Thin disk:Rg2 = (1/2)R2 For an idea chain Experimental Methods 1) IR: vibration and rotation; 2) NMR: chemical shift; 3) chemical analysis, GC, UV and MS; and …. Short range Configuration 1) viscometry: h ~ Vh or Rh; 2) laser light scattering: Rg and Rh; 3) fluorescence: NRET; 4) x-ray and neutron scattering & diffraction; 5) relaxation: mechanical, electrial, optical, ... Long range Conformation

  20. * Primary structures Composition:number & typs of atoms Configuration:how they are connected Homopolymer & heteropolymers: linear, branching, star, grafting, laddle, ... block, seqential, graft, random, ... * Secondary structures Conformation: folding, helix, sheet, ... * Tertiary structures Special arrangements of larger segments to form a complicate structure, e.g., helix Spatial multi-chain aggregates, intra- and inter-chain interaction, e.g., triplethelix & enzyme * Quaternary structures Structures of macromolecules

  21. assembly Small molecules Conventional colloids assembly Macromolecules Polymeric colloids (supramolecules) Physical methods Chemical methods

  22. More Chains Assembled R R R c Self-assembly of rod-coil diblock copolymers in dilute solution Quaternary structures

  23. NH2 DNA P P Lipid bilayer -OOC Cell Membrane Proteins Non-cytosol Single-pass multi-pass Cytosol

  24. fn(M); fw(M); fz(M) M Schulz-Zimm Distribution Poisson Distribution Logarithmic normal distribution Molar mass distributons Mn , Mw , Mz, Mh, ... The end-group, colligative properties MS, light scattering, ultracentrifuge. Absolute methods viscosity, chromatography, FFF electrophoresis, flow birefrigence Relative methods The n-average molar mass The w-average molar mass The z-average molar mass

  25. Natural: DNA, protein, Polysaccharides ... Review Macromolecules Synthetic: different polymers ... Polydispersity, solubility, ... Difference between small and macro-molecules High-order structures R = <R2>1/2 = N2b The statistic nature of chain conformations Rg = <Rg2>1/2 = N2b/6 Rh ~ Rhard with the same D Different distributions of molar mass : Number- MN , weight- MW and Z- MZ ... Different scaling relationships between the size and mass of linear flexible coiled chains

  26. Experimental Methods For polymer chains,molar mass distribution, conformation chain size distribution are important because “M and R” are directly related to properties and performance. for low molar mass chains : end-group; vapor pressure osmometry; NMR; colligative properties; and MALDI-TOF-MS for high molar mass chains : membrane osmometry; ultracentrifugation; and static laser light scattering, Absolute methods which does not require at least two or more narrowly distributed standards with known molar masses fractionation; translational diffusion; viscocity; chromatographic methods; dynamic laser light scattering; and … Relative methods which requires calibration

  27. thermodynamics hydrodynamics In solution In bulk (solid) Macromolecules amorphous crystalline gels - hydrogels In solution: dissolution process Simple & Effective: ~1940’s developed on the basis of a “pseudo lattice” model. *The Flory-Huggins Theory G = H - TS when T = constant The Hildebrand’s solubility equation Condition : no volume change in the mixing F is the attraction force per molar chemical groups. d = e1/2 and e is the cohesive energydensity, i.e., the vaporization energy of unit volume liquid under zero pressure.

  28. po+p po for small molecules p /C = RT/M p for macromolecules p /C = RT/Mn solution solvent The end-group analysis Mn < 10,000 g/mol e.g., Nylon-6 H2N(CH2)5CO-(-NH(CH2)5CO-)n-NH(CH2)5COOH We can titrate the number of ends H2N- and -COOH For a monodisperse sample : M = W/n ; For a polydispersed sample, W = S niMi ; n = S ni , and Mn = W/n Colligative properties why Mn ? The boiling or freezing point change Membrane osmometry There will be special courses to cover them. Here we only ontline their basic principles. MALDI-TOF-MS and NMR

  29. V R = kBNA When one particle agitated by the thermal energy (kBT) undergoes a Brownian motion. It produces a pressure (in solution, it is often called osmotic pressure).

  30. D D The concept of “blob” in polymer science rb = Rg D > Rg The diameter decreases D < Rg rb ~ D

  31. N’ N” N V V V

  32. Laser Light Scattering

  33. i ~ lo -4 i ~ r --2 For N particles i ~ a ‘2 ~ V 2 I = Ni j i q Laser light scattering (LLS) m = a E = 4p eo a ’E P = mp + m E = Eosin(2p vt - f ) Es = k (d2P/dt2) H = e ocE i = <EsHs> = e oc<Es2> Rvv(q) = KCMw Rayleigh ratio : Rvv(q) = Ir2/Io = KCM For a large particle : why <Rg2>Z ? The z-average ?

  34. Cuvette 400祄 pin-hole Focus Lens Position-sensitive Detector Laser Spectra-Physics Helium Neon Laser632.8 nm Wavelength Diode Laser Pumped Nd:YAG Laser532nm Wavelength Laser Monitor diode Cell housing and index matching vat Encoder Stepping motor Static, Classic LLS(time average intensity) Rotating Arm PhotonCounter Polymer : 5x103 - 107 g/molParticles : 2 - 2000 nm Dynamic, Modern LLS(digital time correlator) Preamplifier/Discriminator Dilute solution / suspension C = 10-3 - 10-6 g/ml Photomultiplier tube Laser Light Scattering Spectrometer incorporated with differential refractometer

  35. A2 <R > 2 1/2 g z 1/Mw Static LLS Angular and Concentration dependence of <I> 1 < < 2

  36. slow I I t w + Dw w w w - Dw w0-G w0 w0+G The Siegert relation Dynamic laser light scattering * Intensity fluctuation : The fast the movements, the fast the fluctuation Dynamic LLS fast * Doppler frequency shift : w ~ 1015 Hz ; Dw ~10 5-10 7 Hz It is rather difficult to detect Dw . * Time correlation function:

  37. 0.80 12.00 8.00 ) G 0.60 G( 4.00 0.00 -2 1 - 10 10 0.40 (t,q)-A]/A -1 G / ms (2) 0.20 [g 0.00 0.0 20.0 40.0 60.0 80.0 100.0 t / ms A typical time correlation function of the chains in solution

  38. size temperature The folding of a single homopolymer chain Physical Review Letters 83, 4105 (1999) The transition on surface Physical Review Letters 86, 822 (2001) JACS, 123, 1376 The transition in mixed solvents No additional knotting Physical Review Letters 79, 4092 (1998) Macromolecules, 28, 5225 (1995); 28, 5388 (1995); 28, 8381 (1995); 29, 4998 (1996); 30, 0204 (1997); 30, 7921 (1997); 31, 2972 (1998). Physical Review Letters 77, 3053 (1996) The molten globular state

  39. The collapsing of a single homopolymer chain Mw-1

  40. = 1.54 mm Width ~ 20 ns Ultra-fast infrared laser heating pulse induced conformation change

  41. Kinetics of the coil-to-globule transition of single polymer chains

  42. Time dependent scattering intensity after the laser heating pulse

  43. standards Field w flow Size exclusion chromatorgraphy for small M : Ve = V0 + Vi for large M : Ve = V0 V = V0 + Vi In general : Ve = V0 + s Vi Ve = A’ + B’log ([h]M) Ve = A + B log (M) A’ and B’ In practice , one can obtain Ve and calculate [h]M . If knowing [h], one can find M. * differential refractometer ; * viscometer ; * UV ; and * small angle light scattering Detectors from Ve to M Field flow fractionation (FFF) C(x) = C0 exp(-x/l) where l = D/u = kT/f If d << l < 400 nm, it will be a normal FFF - Smaller ones come out first. If d >> l > 2 mm, it will be a steric FFF - Larger ones come out first.

  44. Temperature glassy melts viscoelastic Shear stress G : the shear modulus Rigidity E : the Young’s modulus Elasticity Normal stress F F D L D L L L Viscoelastic Properties of Bulk Polymers Small molecules (liquid) Crystals and glass Macromolecules (melts) Crystalline and amorphous Stress : F/A = s Several concepts Strain : DL/L = g s = Gg s = Eg The tensile strength : The elongation at break J = 1/G(Compliance) Viscosity (h) E = 2G (1 + m ) m = -(Dd/d)/(DL/L)

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