Do a little research or sign up for a cruise, and you'll easily stumble upon countless packing lists for an expedition cruise to Antarctica. Most of them are generally the same with a few basic, non-negotiable items:
Layers: multiple layers starting with a thermal base layer, an insulating mid-layer, and a waterproof outer layer
*I personally recommend merino wool or Patagonia's Capilene line
Hats, scarves, and waterproof gloves
Thick, warm, wool socks
Sunglasses and sunscreen (it will be sunny, and the sun is strong!)
Having experienced Antarctica firsthand, I have come back with a few additional recommendations of my own that will go a long way toward keeping you safe, warm, dry, and comfortable. Antarctica is technically a desert, so it is very dry, and you will feel it right away!
Good chapstick and lotion (see above re: desert)
Eye drops - again, with the desert. In addition, many sea-sickness preventative medications are drying as well. Add a dry climate and wind, and your eyes will be begging for some drops!
Febreze or essential oils: News flash - penguins are stinky! Their guano has a particularly pungent scent from all the krill they consume, and if you happen to sit down or simply get some on your boots/pants...even the tiniest amount will be forever embedded into all of your belongings in your cabin. Febreze or essential oils will help mitigate!
Notebook: You will want to remember this trip forever and ever and take notes at the incredibly interesting lectures you'll attend. A notebook and pen are crucial.
Small bills (US or EURO): At some of the research bases, you can buy postcards and other small souvenirs, including a shot of vodka at Vernadsky research base!
Ski goggles: Forget sunglasses. On windy days, or if you are kayaking, ski goggles that fully protect your eyes will help immensely.