Polymer Structures. Contents:

Transcription

1 Polymer Structures otets: A. Sythetic polymers derived from petroleum polyolefis (slides 2-4) polyesters ad others (5-6) B. Biological (atural) polymers [biopolymers] polysaccharides (slides 7-10) proteis (slides 11-12) microbial polyesters (slides 13-14). Poly(lactic acid): [sythetic, but derived from a aturally occurrig moomer] (15-16)

2 A. Sythetic polymers derived from petroleum Most commercial polymers are sythetic. The most abudat ad cheapest sythetic polyolefis polymers are polyolefis. Polyolefis are sythesized from olefis (the commo ame for alkees). lefis are obtaied from petroleum. A olefi is a hydrocarbo that cotais at least oe carbocarbo double bod. The simplest olefi is ethylee, The simplest polyolefi is polyethylee (PE). A simple represetatio of polyethylee is where the is the umber of moomer uits. I the polymerizatio, the double bod is lost.

3 If the polyethylee chai is produced to have few ad short braches (side chais) the result is high-desity PE (DPE) If the chai is produced to have may, loger braches, the result is low-desity PE (LDPE)

4 2 l 2 ther polyolefis poly(viyl chloride) (PV) (from ethylee chloride) 3 polypropylee (PP) (from propylee) 2 polystyree (PS) (from styree) Polyolefis are very stable. xidative degradatio is extremely slow. If ot recycled, they are ladfilled or icierated. They are ot biodegradable or compostable. The sigle most importat reaso for their stability is that they have carbo-carbo sigle bods i their backboe.

5 polyesters Polyesters cotai the ester group, 2 2 poly(ethylee terephthalate) (PET) PGA ad PL are biodegradable; the heteroatom (a atom other tha carbo) i the backboe leads to evirometal degradatio by hydrolysis. poly(ε-caprolactoe) (PL) polyglycolic acid (PGA) PET is ot biodegradable i spite of the oxyge i the backboe, because its high crystalliity impedes access of water molecules. Most recycled plastic is PET.

6 ther polymers sythesized from petroleum: 2 2 poly(ethylee glycol) (PEG) (a polyether) 2 poly(viyl alcohol) (PVA) (a polyalcohol) Both are evirometally degradable. PEG has a heteroatom i its backboe ad evirometally degrades by hydrolysis. PVA also degrades by hydrolysis, i spite of its -backboe, because the hydroxyl group o alterate carbo atoms leads to strog iteractios with water.

7 B. Biological (atural) polymers [biopolymers] starch (amylose ad amylopecti) The major polymer compoets of starch are amylose ad amylopecti. 2 2 amylose, a major compoet of starch Amylose is a liear polymer. It is α[1 4]-liked D-glucose. Its molecular weight rages from 2 x 10 5 to 2 x Amylopecti is brached at the hydroxymethyl positio; i.e., it has the same backboe as amylose, but with α[1 6]- liked D-glucose at brach poits. It has molecular weights up to 4 x 10 8.

8 cellulose 2 2 ellulose ad amylose differ oly i the geometric arragemet about the likage.

9 chiti ad chitosa 3 2 N 3 N 2 chiti hitosa is deacetylated chiti. hiti is aother abudat polysaccharide; it is foud i shellfish ad isects ad some fugi.

10 agar 2 Agarose, the mai compoet of agar. carrageea - 3 S 2 Agarose, carrageea, ad algiate are seaweed polysaccharides. They are gellig polysaccharides, ad form good cast films. They have bee used to form ecapsulatig gel beads for drug delivery systems.

11 Proteis N R Structural formula for a geeric protei R represets the side chai of a amio acid. Each specific protei is made up of a characteristic sequece of amio acids. Proteis are polymers formed by the codesatio polymerizatio of amio acids. The carboxyl group of oe amio acid jois with the amio group of aother amio acid, elimiatig a water molecule ad formig a amide likage, called i the case of proteis a peptide bod.

12 Abudat ad commercially importat proteis iclude both aimal ad plat proteis. aimal proteis: gelati (deatured collage) casei whey protei silk kerati plat proteis: soy protei zei from cor(maize) wheat glute potato proteis pea proteis

13 Microbial polyesters:polyhydroxyalkaoates (PAs) Bacteria produce polyesters, icludig polyhydroxyalkaoates (PAs). PAs typically occur as iclusio bodies deposited i graules i the cytoplasm. PAs serve as eergy ad carbo storage materials i bacteria. PAs accumulate whe carbo is i excess but some other utriet limits growth. They are cosumed whe o exteral carbo source is available. The most abudat PA i ature, ad the first to be discovered, is poly-3-hydroxybutyrate (PB). ther PAs have sice bee discovered, icludig those cotaiig hydroxyvalerate uits, as i poly-3-hydroxyvalerate (PV) PB PV

14 opolymers, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PBV), have a rage of properties depedig o compositio. The compositio of the copolymer is cotrolled through the ratio of feedstocks used: glucose or sucrose for butyrate; propioic acid for valerate.

15 . Poly(lactic acid) is a sythetic polymer, but derived from a aturally occurrig moomer, produced through fermetatio. ydrolyzed starch (or some other sugar feedstock) is fed microorgaisms to produce lactic acid, ( 3 ) o large scales. Poly(L-lactic acid) (PLA) is the chemically sythesized from lactic acid. PLA is a polyester ad is biodegradable. 3

16 Poly(lactic acid-co-glycolic acid) is a radom copolymer that has bee used for several types of biomedical applicatio, icludig microcapsules for drug delivery systems. It has also bee used to make orthopedic boe regeeratio-repair materials. 3 m 2 Poly (lactic acid-co-glycolic acid)