Crystalline Properties of Late Generation Polyolefins

Transcription

1 Crystalline Properties of Late Generation Polyolefins R. G. Alamo FAMU-FSU College of Engineering, Tallahassee, Florida Polypropylenes with (3,1) Chain-Walking Defects (Late Ni -diimine catalysts) Precisely Halogen Substituted Polyethylenes (ADMET polymerization /hydrogenation) FSU: C. Ruiz-Orta, J.P. Fernandez-Blazquez, P. Kaner CU: A. Anderson-Wile, G.W. Coates UF: E. Boz, K. Wagener

2 Defects in the poly(propylene) molecule rr triad (stereo) 2,1 erythro (regio) Early Metallocene 2,1 threo (regio) 3,1 (regio) Late Metallocene Defects in propylene copolymers Mainly the comonomer unit : ethylene, 1-butene, 1-hexene, 1-octene

3 Solid State 13 C NMR cpmas Crystal Spectra give direct evidence for partitioning of defects (early metallocenes) PE CH 2 CH 2 CH CH 2 Branch CH 3 PB Propene CH CH 3 Ethyl Branch PB21.1 PB16.8 PB (3,1) ipp ppm The (3,1) defect, and 1-octene and 1-hexene (<13 mol%) are excluded. Ethylene, 1-butene, 1-hexene (> 15 mol%), stereo and regio defects are found in the ipp crystalline regions. Defect Type P CR * = (X C /X B ) Regio (2,1) Erythro 0.3 Stereo (mrrm) 0.5 Ethylene (1 21 mol%) Butene Hexene (>13 mol%) Hexene (< 13 mol%) 0 1-Octene 0 (3,1) Defect 0 X C : Crystal defect concentration X B : Chain defect concentration Alamo et al. Macromolecules, 2000, 33, 6105, Macromolecules, 2008, 41, 95, Polymer, 2009, 50, 832. Polymer, 53, 810, ppm PB

4 T mf ( o C) Melting of early Metal/MAO (metallocene) ipp and ipp copolymers Metallocene Random Propylene Copolymers fixed stereo and regio defects PE PB The (3,1) defect is rejected from the crystal ipp with (3,1) defects should follow the melting behavior of and copolymers Defect Content (mol %) Melting and heat of fusion follow expectations from the comonomer partitioning behavior. Jeon, Alamo et al. Macromolecules, Polymer, 2009, 50, 832.

5 T mp ( o C) Comparative Melting and Degree of Crystallinity Early vs. Late Metal/MAO ipp and copolymers Compared to early metal/mao ipp, ipp with (3,1)-associated defects have lower melting points and dramatically decreased crystallinity rac-4 ipp rac-1 ipp MiPP0.41 PE PB Cystallinity Content (%) / f w rac-4 ipp rac-1 ipp MiPP Defects per 100 monomers Defects per 100 monomers Why?

6 Late Metal/MAO Solution 13 C NMR characterization of defect microstructure (Large number of isolated and multi-monomer defects) (1,2) addition (2,1) + chain walking = (3,1) defect Ruiz-Orta, Alamo et al. Macromolecules 2011, 44, 3436

7 Early vs. Late Metal/MAO ipp and copolymers Early (M 1 ) and Late (M 2 ) Metal/MAO structures for 25 monomers: M 1 M 2 a b d a X B 4 25 Associated with chain walking is: Presence of ethylene runs of similar nature to the ethylene runs in propylene-ethylene copolymers Chain straightening or addition of three C instead of two in the main chain (chain becomes longer for the same number of monomer insertions) For equivalent defect content (4/25), ipp with (3,1)-associated defects have shorter crystallizable sequences. Ruiz-Orta, Alamo et al. Macromolecules 2011, 44, 3436

8 Backbone Crystalline Carbons (%) Defect (b) (Mol%) Defect (d) (Mol%) Complex Polymer designation Late Metal/MAO ipps (two series) T ( C) Total defects (mol%) c M w (Kg/mol) d M w /M n d Rac-4 ipp Rac-4 ipp Rac-4 ipp Rac-4 ipp Rac-4 ipp Rac-4 ipp Rac-4 ipp Rac-1 ipp Rac-1 ipp Rac-1 ipp Rac-1 ipp Rac-1 ipp Rac-1 ipp Rac-1 ipp Rac-1 ipp N Ni Br 2 N N Ni Br 2 N rac -4 rac rac -1 rac At the same overall defect content, rac-4 ipp have shorter isotactic sequence runs. 100 M1 M2 Rac-1 Rac-1 Rac-4 Rac Early M 1 rac- 4 rac Ruiz-Orta, Alamo et al. Macromolecules 2011, 44,

9 T mp ( o C) Melting and Degree of Crystallinity rac-4 ipp rac-1 ipp MiPP0.41 PE PB Cystallinity Content (%) / f w rac-4 ipp rac-1 ipp MiPP Defects per 100 monomers Defects per 100 monomers 1.0 Equilibrium crystallinity equi. cryst. Defect (b ) equi. cryst. f c Flory, P. J. Trans. Faraday Soc. 1955, 51, Crist, B.; Howard, P. R. Macromolecules 1999, 32,

10 Intensity (a.u.) If, as expected the depression in Tm and crystallinity is due to differences in isotactic run length, then other properties that are a direct function of isotactic run length should be affected accordingly: Gamma content (expect higher contents in (3,1)iPP) Crystallite thicknesses (expect lower crystal thickness in (3,1)iPP) Crystallization rates and morphology (lower and more defective expected) Gamma Content 3 mol% ipp3.64 ipp3.51 ipp3.33 (3,1) ipp , (deg) Ruiz-Orta, Alamo et al. Macromolecules 2011, 44, 3436 Hosier, Alamo et al. Macromolecules, 2000, 33, 6105

11 l c (A) Crystallite Thickness and Morphology SAXS PE, ipp with (3,1) associated defects develop thinner and more segmented crystallites 20 (3,1) ipp PE (3,1) ipp PE16.9 (1.5x1.5m) 17 (1x1m) rac-1 ipp15.12 (2 x2m) (100% ) (0% ) (100% )

12 Are (3,1) associated defects generated according to random statistics? AABAAAAAAAAAAAABAAABABAAAAAAAABAAAAAA According to Flory s theory, if B units are non-crystalline, T m does not depend on the chemical nature of the co-unit. T 1 o m 1 T m R H u ln X A Will the melting and crystallinity behavior of (3,1)iPP agree with and copolymers on this basis? M1 Early M: X A = 1-X B M2 a b d a Multimonomer nature M 1 : X B = 4/25 = 0.16 M 2 : X B = 4/22 = 0.18 On crystallizable and non-crystallizable units, late M ipp have higher contents of non-crystallizable units

13 T mp ( o C) X c (%) Comparative Analysis on the basis of Equilibrium Theory M1 M2 a b d a T 1 o m 1 T m R H u ln X A Late M: Correction to X A from extra backbone C due to chain straightening Y A 2X A (3a 2X A 8 6 b c d 2 f 2st) rac-4 ipp rac-1 ipp MiPP (1-X A ) or (1-Y A ) (Mol%) (1-X A ) or (1-Y A ) (Mol%) rac-1 ipp MiPP0.41, and (3,1) ipp display the same Tm or crystallinity/defect composition behavior. The generation of (3,1)- associated defects is random Ruiz-Orta, Alamo et al. Macromolecules 2011, 44, 3436

14 Conclusions Late Metal/MAO ipp with (3,1) defects (3,1) is the most effective defect to decrease crystallinity. Crystalline ipp contain isolated and successive groups of (2,1) and (3,1)- enchainments. These are unique defects of a extended multimonomer nature that effectively lower the melting points and have a dramatic depression of crystallinity in reference to propylene 1-alkene copolymers. The thermodynamic properties adhere to the exclusion model, indicating that the (3,1)-associated defects are random-bulky or generated following random statistics.