I have never heard the acrylic resin referred to as "Plexiglas". Plexiglas is the tradename owned by Rohm and Hass for its solid acrylic sheeting. It was,by the way, invented in my wife's home town in Germany. (Just an aside)

I do believe Rohm and Hass ( I think it is now just Rohm) is the biggest supplier of acrylic resins to the paint industry. They publish an E-Mail newsletter for the painting industry to which I subscribe.

You seem to feel that acrylic paints are somewhat inferior at proteting the wooden substrate? My experience is that acrylics are vastly superior to oil paints for general exterior housepainting. They allow the house to breath, are far more color fast and its elastic nature allows it to flex with the wooden substrate better.

Being from the old school, I still like oil primers for their ability to not raise the grain, to seal in tannins and other stains and to penetrate deep into the wood's fiber. That being said, the newer acrylic primers seem to be approaching the performance of oil primers.

I have used some of the new Behr Ultra acrylic self-priming housepaint on a pergola I built three years ago. It has just come through its 3rd Oregon winter looking great. It got a "prime" coat of the paint and a finish coat, with minor touch-up due to construction dings during assembly. Apparently, its nano technology is not just some advertising agent's hype.