Gelatin supplies 2 important functions in emulsion making. Gelatin functions as a peptizing agent and as a vehicle.
As a peptizer, it prevents silver halide from falling to the bottom of your beaker in one lump or a few large lumps. Instead, gelatin suspends the crystals in a creamy mixture.
As a vehicle, it supplies a viscous "melt" that can be coated and hardened and which remains intact through the processing procedure. It must be transparent and colorless.
If you select a material for emulsion making it must do all of the above. At EK we never found a single polymer that could do all of the above. We found two families of polymers that supplied the features of a peptizing agent and as a vehicle individually. That is about it.
Bill has had some success with the Silanes. I hope this is of use to all of us.
Yes, but in terms of image aesthetics is it really necessary. Salt prints, Van Dyke and Platinum don't need it.
Some salt prints use egg albumen which is gelatin! Gelatian supplies a glossy surface or carries matting agents for a matte surface or other effects. But needed? No, unless you want SPEED!!! Or perhaps COLOR, or even INSTANT!!!
There is also uniform coating, high speed coating and a host of other things.
I do not know if this would apply to what you are trying to accomplish and I do not know much about chemistry, but 2 things come to mind if looking for a type of plant that would make a gelatin like product.
One would be agar and the other carrageenan, one is a culture product of algae used for growing mushrooms and the other is obtained from seaweed used as a common ingredient in milk products like ice cream.
They are both gelatin-like.
I have no idea how these would react to any type of photographic process or if they would have application at all and I also don't think these would be very permanent.
Could these products be used in some type of non-silver based photography?
If you want an alternative to gelatin for coating negative-producing plates, just get into wet plate collodion. The chemistry is messy, the results are irregular, but you are dealing with a 100% animal-free product. Silver nitrate, collodion (cotton fibers dissolved in alcohol), ether, cadmium bromide, potassium bromide or iodide, sugar, ferrous sulfate, and cyanide (or hypo). All plant-based or inorganic.