Help to write to a file

Dear all:

I am having some problems to use the function "sink()". Basically I am doing
a loop over two files which contain unit-root variables. Then on a loop, I
extract every i element of both files to create an object called z. If z
meets some requirements, then I perform a unit root test (ADF test),
otherwise not. As this process is repeated several times, for each i I want
to get the summary of the ADF test on a common file. For that I use the
function "sink()". My code runs fine, but I do not get anything written on
the text file where my results are supposed to be saved. The code is below

setwd("C:\\Users\\Sergio Ren?\\Dropbox\\R")

library("urca")

P1<-read.csv("2R_EQ_P_R1_500.csv")
P2<-read.csv("2R_EQ_P_R2_500.csv")

d<-(1:1000)
sink ("ADF_results_b_1.txt")

for (i in seq(d))
{
z.1<-P1[i]*-1-P2[i]*-1
if (all(z.1<=0)) {r=1} else {if (all(z.1>=0)) {r=1} else {r=2}}
if (r==1) {ADF<-ur.df(ts(z.1), lags=1, type='drift')}
if (r==1) {summary(ADF)}
}
sink()

Any suggestion of what I might be doing wroong?