On-line LC(GPC/SEC)-NMR of Complex Mixtures

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1 On-line LC(GPC/SEC)-NMR of Complex Mixtures 1 Jian Wu, Miroslav Janco Analytical Sciences, Core R&D The Dow Chemical Co. Collegeville, PA (International Symposium GPC/SEC and Related Techniques)

2 Outline Background Solvent suppression by PFG diffusion LC-NMR of polymer mixtures Polymer Blend of pstyrene and p(sty/ba) GPC-NMR of polymers (composition as a function of MW) Mixture of psty, pba and pba-b-mma (on-flow/stop-flow) Mixture of psty and psty-b-butadiene P(BO/EO) mixture in different mobile phases Grafting of polyol to PDMS by GPC-2D-NMR 2

3 LC(GPC)-NMR of Complex Mixtures Application Polymer composition as a function of MW Polymer grafting/blending Impurity and metabolite analyses Instrument setup CryoFit (30µL Flow cell) 20 µl (HPLC) 100 µl (SEC) UV ELSD A cryofit insert for a 5 mm cryoprobe in a 600 MHz spectrometer enables higher sensitivity. L 15 = ft; 15 ; 0.25 ID = mm 2 mm ID Operation modes: Stop flow and On flow 3

4 Solvent suppression by PFG diffusion NMR Spectra of pmma, pba, p(mma/ba) Mixture in THF A) Without solvent suppression B) With solvent suppression THF THF MMA -OCH 3 Good solvent suppression is critical to LC-NMR BA -OCH ppm ppm First to propose and demonstrate the PFG-diffusion method in LC(GPC)-NMR for solvent suppression. This method is based on the different diffusion properties between polymers and small molecules. (Ref: Wu, D.; Chen, A.; Johnson, C. J. Magn. Reson. A 1995, 115, Wu, J.; Beshah, K. ACS Symposium, 2003, 834, ) 4

5 On-line HPLC-NMR Reversed-phase Peak 2 psty HPLC Mixture of p(sty-b-mma) and psty Solvent gradient: 100% CH 3 CN to 100% CHCl 3 in 10 min Column: Supelco C18 (250x4.6 mm ID) Detection: 254 nm Peak 1 psty-b-mma Peak 1: psty-b-mma H 6S 2-4 Peak 2: psty H 2 C psty 4 1 5

6 GPC-NMR of psty, pba, pba-b-mma mixture phase: CHCl3 4kMobile Detector: t ELSD Sample Concentration: 10mg/g/component Column set: 2PLgel Mixed D (300x7.5 mm ID) pst tyrene Mn~ ~630k pba A-b-MMA Mn n~87k pba Mn~2 GPC Peak H 2 2 C psty pstyrene Mn~630k 1-2 Peak 2 8 pba-b-mma Mn~87k 12 7S H Peak H 2 C O pba O 9 pba Mn~24k

7 On-flow GPC-NMR of psty, pba, pba-b-mma mixture pstyrene pba pmma pba Low MW BA MMA High MW Styrene 7 The data showed NMR chemical signals as a function of MW, with high-mw psty eluting first and low-mw pba eluting last.

8 GPC chromatograms of pstyrene and psty-b-butadiene Mixture ELS psty-b-bd ELS pstyrene MW: 222k MW: 7k tensity Int UV Retention time (min.) The GPC chromatograms of the pstyrene and psty-b-butadiene mixture with ELS (green) and UV (blue) detections. A Waters UltraStyragel Linear column (30 cmx7.8 mm ID) was used with THF as eluent (flow rate: 0.8 ml/min). 8

9 On-line GPC-NMR on pstyrene and p(sty-b-butadiene) Mixture GPC (min) H 2 C 1 2 psty t1 (min) F2 (ppm) 5.5 Proton Chemical Shift The on-flow GPC-NMR on the mixture of pstyrene and psty-b-butadiene, showing the unsaturated protons of butadiene and the aromatic protons of styrene as a function of GPC retention time. 9

10 On-line GPC-NMR of p(bo/eo) copolymer mixture in THF A p(butylene Oxide(BO)/Ethylene Oxide (EO)) mixture showed multiple GPC peaks Our objective was to understand the polymer composition as a function of its MW GPC Peak 1 p(bo/eo) Peak 2 pbo Peak 2: pbo BO EO Peak 1: p(bo/eo) THF THF BO Mobile phase: THF Column set: 2PLgel Mixed D (300x7.5 mm ID) The Challenge: The EO signal partially overlaps the THF signal. 10

11 On-line GPC-NMR of p(bo/eo) copolymer mixture in CHCl 3 Improved method: Changing g mobile phase to CHCl C 3! GPC EtOH Peak 2: pbo EtOH Peak 1 Peak 2 p(bo/eo) pbo BO EO Peak 1: p(bo/eo) BO Mobile phase: CHClC 3 Column set: 2PLgel Mixed D (300x7.5 mm ID) The GPC-NMR data shows that the high MW peak contains both EO and BO, while the low MW polymer peak is composed of homo pbo. 11

12 On-flow GPC-NMR of p(eo/bo) copolymer mixture High Mw This data shows that the EO/BO ratio changes as a function of MW, with low MW polymers containing mostly pbo. EO/BO molar ratio ~1.0/0.30 ~1.0/0.28 ~1.0/0.31 ~1.0/0.38 EO ~1.0/0.53 BO ~1.0/0.96 ~1.0/2.53 Low Mw ~1.0/

13 On-line GPC-2D NMR of PDMS/EO/PO Polymer Mixture Objective: To understand how the Polyol is grafted to PDMS GPC PDMS/PEO/PPO PEO/PPO Mobile phase: CHCl 3 Column set: 2PLgel Mixed D (300x7.5 mm ID) Proposed Grafting Chemistry 13 The CryoFit / CHCl 3 provides excellent sensitivity for 2D NMR experiment The GPC-2D NMR generates both 13 C and 1 H NMR data plus their correlation. This enables detailed structural elucidation at the molecular level.

14 Summary Demonstrated solvent suppression methods by PFG diffusion in LC(GPC)-NMR Successfully addressed polymer blending by LC-NMR and studied polymer composition as function of MW by GPC-NMR Using GPC-NMR, we completely characterized a p(bo/eo) mixture Showed the BO content increased as the MW decreased The low-mw polymer peak is composed of homo pbo Enabled our business to re-design synthesis Successful characterization of the PDMS/PEO/PPO polymer by GPC-2D NMR Understood its grafting chemistry Provided critical inputs for its synthesis 14

15 Acknowledgments John Rabasco Yuhua Tong Kebede Beshah David Redwine Jun Qi Jim Alexander Stewart Williams David Meunier Alan Nakatani Bruce Bell Zhe Zhou Paul O Connor Tianlan Zhang Jim DeFelippis Matt Miller Wayde Konze Robert Krull, Bruker Biospin 15