Edit: As Atspulgs comment suggest, you can achieve the same without jQuery using the querySelector:
document.head.innerHTML += '<link rel="stylesheet" href="styles.css" type="text/css"/>';
Older answer below.
You could use the jQuery library to select your head element and append HTML to it, in a manner like:
$('head').append('<link rel="stylesheet" href="style2.css" type="text/css" />');
You can find a complete tutorial for this problem here