Characterisation of Branched Co-Polymers by Triple and Tetra-Detection GPC/SEC Sue Lewis Viscotek Europe, Crowthorne, UK. [email protected] Samples provided by Dr Robert Hunter of Unilever Research and Strathclyde University Introduction Experimental Polymers which are complex both in structure and composition present many difficulties for conventional GPC/SEC techniques. Triple detection GPC/SEC, using refractive index, light scattering and viscometer detectors overcomes these difficulties and shows the structural differences between samples by measuring molecular weight, intrinsic viscosity and molecular size across the distribution. By adding a UV detector signal (tetra detection) the compositional differences between samples can be identified and compensated for. 4 samples of co-polymer were analysed: 1 linear and 3 branched (Low, Mid and High). The samples were run on a Viscotek Tetra-Detector GPC system with OmniSEC software. Data on molecular weight, intrinsic viscosity and molecular size were obtained directly. Using the OmniSEC software branching view, the amount of branching was determined in the 3 samples relative to the linear reference. The UV detector was used together with the RI detector to show the chemical compositional differences in the branched samples. Chromatograms Linear co-polymer Branched co-polymer Data File: 2005-12-06_02;08;20_7-Low_Branching_02.vdt Method: UL1-LMW-0001.vcm Data File: 2005-12-06_01;06;15_6-Linear_02.vdt Method: UL1-LMW-0001.vcm -50.00 -40.00 Red = Refractive Index (RI) -58.00 -67.00 Green = Light Scattering (LS) -76.00 -85.00 Instrument: -94.00 -66.00 Refractive Index Response (mV) Blue = Viscometer (V) -58.00 -74.00 -82.00 -90.00 -98.00 -106.00 -103.00 Viscotek TDA-GPCmax system -114.00 -112.00 2 x Viscogel Columns -121.00 -122.00 -130.00 -130.00 5.00 7.50 10.00 12.50 15.00 17.50 20.00 22.50 25.00 27.50 THF @ 1ml/min 30.00 5.00 7.50 10.00 12.50 15.00 17.50 20.00 22.50 25.00 27.50 30.00 Retention Volume (m L) Retention Volume (mL) Results Calculated Data Mw 14,488 87,918 84,264 79,075 Mn 4,838 5,158 4,168 6,159 IV 0.0927 0.1080 0.0953 0.0946 Mark Houwink Overlays The Mark Houwink plot below shows clearly the progression of branching from Linear to Low to Mid/High. dn/dc 0.083 0.083 0.092 0.093 Branching view - Low Branching Sample The Mark Houwink plot for the linear sample was extrapolated and used to measure branching in the other samples. Overlay Plot: Log Intrinsic Viscosity Vs. Log Molecular Weight Method: UL1-Branching-Auto-0003.vcm 0.00 2005-12-06_00;35;13_6-Linear_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_01;37;17_7-Low_Branching_01.vdt : UL1-Branching-Auto-0003.vcm -0.10 2005-12-06_02;39;21_8-Mid_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_03;41;23_9-High_Branching_01.vdt : UL1-Branching-Auto-0003.vcm . 2 0 0 5 -1 2 -0 6 _ 0 0 ;3 5 ;1 3 _ 6 -L in e a r_ 0 1 .v d t / M e th o d : U L 1 -B ra n ch in g -A u to - 0 0 0 3 .vc m Sample ID Linear Low Branching Mid Branching High Branching 2005-12-06_01;37;17_7-Low_Branching_01.vdt - Branching Data View -0.20 0.500 0.400 -0.30 Lambda 0 2.68 3.82 4.99 0.200 -0.40 -0.50 0.000 -0.60 -0.70 -0.80 -0.400 -0.600 -0.90 -0.800 -1.00 Lambda is branching frequency, in this case expressed as branches per 1000 MMA units or 98,000 Da. The Mid and High samples are very similar in branching level but due to the sensitivity of the technique they are still clearly differentiated. -1.10 -1.000 -1.20 -1.200 -1.30 -1.400 -1.500 -1.40 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 2.000 7.0 2.400 2.700 3.000 3.300 3.600 3.900 4.200 4.500 4.800 5.100 5.400 5.700 6.000 6.300 6.600 7.000 Log Molecular Weight Log Molecular Weight 368.20 2005-12-06_01;37;17_7-Low_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_02;39;21_8-Mid_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_03;41;23_9-High_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 341.90 315.60 0.80 g` 0.70 Bn 289.30 263.00 236.70 0.60 210.40 184.10 0.50 157.80 0.40 131.50 105.20 0.30 78.90 0.20 52.60 26.30 0.10 -20.00 0.00 3.5 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.5 3.0 3.2 3.4 3.6 3.8 1.500 1.000 6.0 0.500 0.0 0.000 10.00 13.6 15.3 17.0 Retention Volume (mL) 20.00 R e fra ctive In d ex R esp on se (m V ) 2.000 RI / UV Ratio 7-Low_Branching_01.vdt Method: UL 12.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 Log Molecular Weight Log Molecular Weight 22.0 18.0 4.0 8-Mid_Branching_01.vdt Method: UL 2.000 1.500 12.0 1.000 6.0 0.500 0.0 0.000 13.6 15.3 17.0 6.4 6.5 7.5 0 2005-12 -06_01;37;1 7_7-Low_Branching_01 .vdt : UL1-Branching-Au to-0003.vcm 2005-12 -06_02;39;2 1_8-Mid_Branching_01 .vdt : UL1-Branching-Auto-0003.vcm 2005-12 -06_03;41;2 3_9-High_Branching_0 1.vdt : UL1-Branching-Au to-0003.vcm 7.0 0 6.5 0 Lambda 6.0 0 5.5 0 5.0 0 4.5 0 4.0 0 3.5 0 3.0 0 2.5 0 2.0 0 1.5 0 1.0 0 0.3 2 3.5 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 Log Molecul ar Weight 22.0 18.0 10.00 6.2 8.0 0 20.00 Retention Volume (mL) 9-High_Branching_01.vdt Method: UL 22.0 18.0 2.000 12.0 1.000 6.0 0.500 1.500 0.0 0.000 10.00 13.6 15.3 17.0 20.00 Retention Volume (mL) CONCLUSIONS • Triple detection GPC/SEC measures molecular weight, intrinsic viscosity, hydrodynamic radius and branching • The UV detector enables correction of differences in chemical composition for true molecular weight . • Tetra detection GPC/SEC enables complete characterisation of branched co-polymers R I / U V R a tio 400.00 2005-12-06_01;37;17_7-Low_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_02;39;21_8-Mid_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_03;41;23_9-High_Branching_01.vdt : UL1-Branching-Auto-0003.vcm 2005-12-06_0 1;37;17_7-Low_Branching_01 .vdt / Method: UL1-Branching -Auto-0003.vcm 0.90 Overlay Plot: Lambda Vs . Log Molecu lar Weight Method: UL1-Branchi ng-Auto-000 3.vcm Overlay Plot: Branching Vs. Log Molecular Weight Method: UL1-Branching-Auto-0003.vcm Overlay Plot: g' Vs. Log Molecular Weight Method: UL1-Branching-Auto-0003.vcm 1.00 R e fra ctive In d e x R e sp o n se (m V) 2005-12-06_01;37;17_7-Low_Branching_01.vdt / Method: UL1-Branching-Auto-0003.vcm The values of g’, branching number (Bn) and Lambda can be plotted against molecular weight to illustrate differences in branching within the set of samples as shown in the plots to the right. The branching frequency plot is particularly revealing as it shows how the branching is distributed across the molecular weight distribution. Using the integrated UV detector in the tetradetector instrument, the RI/UV ratio across each sample chromatogram was plotted (right). These show clearly that the chemical compositions of the 3 co-polymers samples are not the same. Using either measured or supplied values of the refractive index increment and UV absorption coefficients, the OmniSEC co-polymer method can be used to correct the concentration data. This results in even more accurate molecular weight and branching information. -0.200 R I / U V R a tio Bn 0 17.8 26.2 29.2 L o g In trin s ic V is c o s ity Rh 2.60 4.47 4.07 4.12 2005-12-06_01;37;17_7-Low_Branching_01.vdt / Method: UL1-Branching-Auto-0003.vcm Sample ID Linear Low Branching Mid Branching High Branching R efractive Index R esponse (mV) Refractive Index Response (mV) -49.00 6.2 6.4 6.5
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