Making Functional Biodegradable Polymers

Acrylic acid and derivatives have been free radically grafted onto the backbone of biodegradable polycaprolactone and poly(lactic-co-glycolic acid). These functionalized biocompatible materials are useful as drug delivery agents. 

Preparation of Poly[(Lactic-co-Glycolic Acid)-g-Acrylic Acid] 

To prepare the graft copolymer, poly [(lactic-co-glycolic acid) (5.7 g) was dissolved in acrylic acid (5.7 g) and, upon dissolution, treated with 98% 2,2 -azobisisobutyronitrile (0.014 g). The mixture was then heated to 70°C and continued heating until the reaction mixture solidified. The solid was then placed into a vacuum oven to remove unreacted acrylic acid, and the product was isolated. 

TABLE 1. Biodegradable poly[(lactic-co-glycolic acid) substrates free radically functionalized with grafted acrylic acid or 2-hydroxylethyl acrylate. 

The solution behavior of the Step 1 product was evaluated using a Coulter tester. In this test NaOH was used to raise the solution s pH to 9.6 whereupon a milky solution with an average particle size of 2 pwas formed. By one additional day, particle aggregation and precipitation became significant. When the solution pH was raised to 13.7, a clear solution formed with an average particle size of 347 run. 

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Title Methods of Making Functional Biodegradable Polymers... 

For much of the last century, scientists attempted to make useful plastics from hydroxy adds such as glycolic and lactic acids. Poly(glycolic acid) was first prepared in 1954, but was not commercially developed because of its poor thermal stability and ease of hydrolysis. It did not seem like a useful polymer. Approximately 20 years later it found use in medicine as the first synthetic suture material, useful because of its tendency to undergo hydrolysis. After the suture has served its function, the polymer biodegrades and the products are assimilated (Li and Vert 1995). Since then, suture materials, prosthetics, artificial skin, dental implants, and other surgical devices made from polymers and copolymers of hydroxy carboxylic acids have been commercialized (Edlund and Albertsson 2002). 

Albumin is a water-soluble protein representing 50% of total plasma mass and is the most copious protein in human blood plasma. The pre-proalbumins synthesized in the liver are further processed and released into the circulatory system. Albumin is known to degrade in all tissues in the body and shows excellent blood compatibility, making it a great choice of biodegradable polymer for medical applications [40]. Albumin can be effortlessly modified, due to the presence of functional groups and desirable solubility, into various shapes and forms such as membranes, microspheres, nanofibers and nanospheres. 

The principal used in polymer-clay nanocomposites leads the individual clay layers as well as the polymer chains to function more effectively with numerous improved properties such as high moduli, increased strength and heat resistance, decreased gas permeability and flammability, increased biodegradability of biodegradable polymers, and attractive electrical properties when compared to virgin polymers or conventional micro- and macrocomposites [37]. These properties make them ideal materials for applications in food packaging, structural automotive components, and electronics among others. 

Bhattacharya M., Jacob J., Vaidya U. Method of grafting functional groups to synthetic polymers for making biodegradable plastics. World patent (US) WO9747670 (1997). 

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