Page 184 - Academic Press Encyclopedia of Physical Science and Technology 3rd Polymer

P1: GKY/MBQ P2: GLQ Final Pages
Encyclopedia of Physical Science and Technology en012i-947 July 26, 2001 11:11

692 Polymers, Inorganic and Organometallic

TABLE V Some Common Aluminosilicate Minerals, General Formulas, and Applications
Structural type Example General formula Applications
Sheet Mica K(Mg, Fe) 3 [(HO) 2 AlSi 3 O 10 ] Electronics (capacitors, diodes), cosmetics (powders)
3D Feldspar K[(AlO 2 )(SiO 2 ) 3 ] Glass, ceramics, semiprecious stones
Zeolites Na 13 Ca 11 Mg 9 KAl 55 Si 137 O 384 Water softener, gas separation and purification
Molecular sieves (A) Na 12 [(AlO 2 ) 12 (SiO 2 ) 12 · xH 2 O] Small-molecule (4 ˚ A) absorber (e.g., H 2 O)
Molecular sieves (X) Na 86 [(AlO 2 ) 86 (SiO 2 ) 106 · xH 2 O] Medium-molecule (8 ˚ A) absorber (e.g., CH 3 OH)

tin in which tin is part of or pendant to the polymer back- (Fig. 35D) using free radical, ionic, or coordination cata-
II
bone. Examples of the former are Sn X 2 (X = Cl, OCH 3 ), lysts. These polymers have the Sn moiety pendant to the
which has an extended chain structure of three-coordinate polymer backbone. Some of these polymers readily re-
Sn with two X units in the chain (Fig. 35A), and lease the tin moiety in water and have potent antifouling,
IV
(CH 3 ) 3 Sn Y(Y = F, azide), which is a strongly asso- antifungal, and antibacterial properties. However, their
ciated polymer of five-coordinate Sn with Y units toxicity to the environment has precluded widespread
forming bridges between tin moieties (Fig. 35B, C). commercial applications. In an effort to circumvent the
IV
(CH ) 2 Sn F 2 forms a 2D infinite-sheet structure in which rapid hydrolytic release problem, styrene polymers with
3
each Sn is in an octahedral environment with the methyl n-Bu 3 Sn bonded directly to the phenyl group have been
groupslyingaboveandbelowtheplaneofthesheetandthe prepared.
F atoms forming bridges to four Sn atoms. Other types of Unusual “cage” oligomeric organotin carboxylates that
tin-containing polymers with Sn O M (M = Si, Ti, are prepared by the condensation of organostannoic acids
and B) units in the chain have also been prepared. Some with carboxylic acids or their salts are mainly tetramers

of these polymers have uses as plasticizers, fungicides for and hexamers with formula [RSn(O)O CR ] 4or6 . Evi-
2
paints, fillers and reinforcing agents, and resin additives dence suggests that the reaction proceeds through the for-
to enhance thermal and mechanical properties. mation of ladder type intermediates (see Fig. 6) prior to
Vinyl esters such as tributyltin methacrylate can un- closure to yield a stable drum-shaped product (Fig. 35E;
dergo polymerization to poly(tributyltin methacrylate) only one of six carboxylate units is shown).

FIGURE 36 Examples of transition metal coordination polymers.