I am planning to fabricate spongy like polymeric scaffold for tissue engineering applications. Is there any possibility to make spongy material with block copolymeric system?
This question can be answered by specific example on polyuerthanes which are used widely as spongy polymers. Polyurethanes are linear polymers that have chains containing urethane groups (-NHCO2). These polymers are made by reaction of a diisocyanate (OCN-R-NCO) with a diol (HO-R-OH). If the reaction is done by exclusion of moisture,then solid tough polymers are obtained.
If little water is added deliberately during the polymerization, a side reaction occurs: R-N=C=O + H2O → [R-NH-COOH] → R-NH2 + CO2(g)
The evolved CO2 acts as blowing agent within the polymer matrix causing foaming which ends up in forming spongy polymer. We can have an alternative to the mentioned processing by injecting within the polymer a blowing agent “usually simple organic volatile compound”.
Sponge-like materials will generally be foams with a structural polymer of viscoelastic character. The viscoelastic component gives elasticity to the structure while the viscous component has a time-retarding character. A contrast is between a natural rubber foam (elastic) and a polyurethane foam (viscoelastic). Control of foam density, pore size and its distribution contribute to properties. A two phase material can be a thermoplastic polyurethane that can contain a polyol from polycaprolactone as a biocompatible material that may be important for tissue engineering. Alternatively a cross-linked polyurethane can be prepared from castor oil (ricinoleic acid with reactive hydroxyl groups) with a diisocyanate (this component is not bio-friendly, though with complete reaction the problem is minimised). A foam is produced from the small amount of moisture in the castor oil, though known amounts of moisture may need to be added to give reproducible foams. I have made these foams with cellulose filler to enhance stiffness. Thermoplastic elastomeric foams are more difficult to make since a melt is required. I have limited examples in this answer, however many other related polymer systems can be used.. and they are generally cross linked or of two-phase structure.
@Dr.Nizar Matar Thank you for your explanation. But what would be the effect if I want to go with Amphiphillic block copolymer system? IF i can go with Amphiphillic block copolymer system whether hydrophobic group must be more or hydrophillic group must be more? and Is there any case that only a polymer which can be made into hydrogel only will be having the ability to make foams or spongy like structures?
The urethane systems use a reaction between water and isocyanate to produce the foaming gas (CO2). You can also use blowing agents to produce foam. These materials decompose to produce gas, usually nitrogen. You can also physically inject gas into your system. Both of these other processes can be somewhat tricky and may take a bit of work.
I do not know what your interest or what material you would be interested. In addition to polyurethane formulations, you can also get expanded materials (hardness ranging from soft to hard) such as copolymer of ethylene and vinyl acetate.
Below are some links if you are interested to work
http://www.scielo.br/pdf/po/v24n1/a10v24n1.pdf
http://www.periodicos.ulbra.br/index.php/acta/article/view/145
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