library(purrr)
library(dplyr)
library(microbenchmark)

list <- map(1:1000, function(x) rep("a", 100))

f1 <- function(list){
  reduce(list, c)
}

f2 <- function(list){
  map(list, function(x) data_frame(char = x)) %>%
    bind_rows() %>%
    .$char
}

microbenchmark(f1(list), f2(list))