You can try this :
Html code :
<input type="button" id="bthPopUp" value="Test Popup title" onclick="OpenPopUp()" />
function OpenPopUp() {
var win = window.open('', 'Window', 'menubar=0, location=0 ,toolbar=0, resizable=1 ,status=1, scrollbars=1');
if (win.document) {
win.document.title = "My New Title";
}
}
Hope it helps you.