Branched Polymer SEC Data

A synthetic dataset containing SEC chromatograms of linear, branched, and star polymers, designed for demonstrating branching analysis using multi-detector SEC.

Usage

sec_branched

Format

A tibble with 5,608 rows and 10 columns:

sample_id

Character. Sample identifier (e.g., "Linear-50K")

elution_time

Numeric. Elution time in minutes

ri_signal

Numeric. Refractive index detector signal

visc_signal

Numeric. Viscometer detector signal

mals_signal

Numeric. Multi-angle light scattering signal

topology

Character. Polymer topology: "linear", "branched", or "star"

mw

Numeric. Weight-average molecular weight in Da

branching_index

Numeric. Branching index g' (1.0 for linear)

intrinsic_visc

Numeric. Intrinsic viscosity in mL/g

rg

Numeric. Radius of gyration in nm

Source

Synthetic data generated for package testing and examples.

Details

The dataset includes polyethylene-like samples with three topologies:

• Linear polymers (g' = 1.0) at 50K, 100K, 200K MW

• Branched polymers (g' = 0.55-0.75) at same MW range

• Star polymers (g' = 0.50-0.60) at 50K, 100K MW

Key Observation: At the same molecular weight, branched polymers have smaller hydrodynamic volume and elute LATER than their linear counterparts. This is the basis for branching analysis by comparing SEC retention to absolute MW from MALS.

Branching Index (g'): g' = \([\eta]_{branched}\) / \([\eta]_{linear}\) at same MW

Values less than 1.0 indicate branching. Lower values mean more compact (more branched) structures.

Typical Workflow:

1. Apply step_sec_mals for absolute MW

2. Apply step_sec_viscometer for intrinsic viscosity

3. Use measure_branching_index to calculate g'

4. Plot Mark-Houwink relationship to compare topologies

See also

Other sec-data: sec_calibration_standards, sec_copolymer, sec_pmma_standards, sec_protein, sec_ps_standards, sec_raw_multidetector, sec_raw_standards, sec_raw_unknowns, sec_system_suitability, sec_triple_detect

Examples

data(sec_branched)

# Compare topologies
unique(sec_branched[, c("sample_id", "topology", "mw", "branching_index")])
#> # A tibble: 8 × 4
#>   sample_id   topology     mw branching_index
#>   <chr>       <chr>     <dbl>           <dbl>
#> 1 Linear-50K  linear    50000            1   
#> 2 Linear-100K linear   100000            1   
#> 3 Linear-200K linear   200000            1   
#> 4 Branch-50K  branched  50000            0.75
#> 5 Branch-100K branched 100000            0.65
#> 6 Branch-200K branched 200000            0.55
#> 7 Star-50K    star      50000            0.6 
#> 8 Star-100K   star     100000            0.5 

# Plot linear vs branched at same MW
if (requireNamespace("ggplot2", quietly = TRUE)) {
  library(ggplot2)
  library(dplyr)

  sec_branched |>
    filter(mw == 100000) |>
    ggplot(aes(elution_time, ri_signal, color = topology)) +
    geom_line() +
    labs(
      x = "Elution Time (min)",
      y = "RI Signal",
      title = "100K MW: Linear vs Branched vs Star",
      subtitle = "Branched polymers elute later (smaller Vh)"
    ) +
    theme_minimal()
}