Early Polymers

FIGURE 4.1 Polymers are one of the most common and versatile synthetic materials. They can be formed into almost any shape imaginable. 

Bakelite was the first truly synthetic polymer to be produced and was trademarked in 1907 by Belgian scientist Leo Hendrik Baekeland. This new material was formed from a combination of phenol and formaldehyde and as an early plastic enjoyed wide use in a variety of applications, from household objects, knobs, and radio casings to costume jewelry and telephones. The new plastic was hard wearing and chemically resistant. It could be infused with filler materials such as sawdust or fabric and easily molded to the desired shape. Nylon was another early and hugely successful polymer. Developed in the 1930s, this extremely durable and malleable polymer was particularly useful during World War II for its ability to be drawn into very strong fibers for parachute production. 

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The observation in 1949 (4) that isobutyl vinyl ether (IBVE) can be polymerized with stereoregularity ushered in the stereochemical study of polymers, eventually leading to the development of stereoregular polypropylene. In fact, vinyl ethers were key monomers in the early polymer Hterature. Eor example, ethyl vinyl ether (EVE) was first polymerized in the presence of iodine in 1878 and the overall polymerization was systematically studied during the 1920s (5). There has been much academic interest in living cationic polymerization of vinyl ethers and in the unusual compatibiUty of poly(MVE) with polystyrene. 

Although first prepared about 1930 by scientists at the German chemical company of IG Farben the early products showed no properties meriting production on technical grounds. However, towards the end of the 1930s commercial production of the copolymer commenced in Germany as Buna S. (The term Buna arose from the fact that the early polymers of butadiene were made by sodium (Na) catalysed... 

Horns and hooves were the raw materials for the early polymer preparations. These materials were ground up and treated in various ways so that they could be fabricated into such items as combs to use for ladies hair, and other specialty things of that sort. The next development was the use of cellulose from cotton or from wood as the raw material which was studied for making films and fibers. Work on the cellulose structure had provided information that it was a hydroxylated product, and by converting the hydroxyls to esters, the natural cellulose could be turned into a soluble material, which was spun into fibers and cast into films to make the first cellulose rayon-type material and cellulose films. 

Early polymer scientists examined natural polymers to gain insight into the complex chemistry that might be possible. Advances in analytical chemistry over the past 70 years have allowed detailed characterization of the chemistry of life and have provided us with an opportunity to easily revisit these early polymer discovery days and rediscover key polymer lessons from natural polymers. 

Single-molecule theories originated in early polymer physics work (45) to describe the flow behavior of very dilute polymer solutions, which are free of interpolymer chain effects. Most commonly, the macromolecular chain, capable of viscoelastic response, is represented by the well-known bead-spring model or cartoon, shown in Fig. 3.8(a), which consists of a series of small spheres connected to elastic springs. 

However, for nonspherical particles, rotational Brownian motion effects already arise at 0(0). In the case of ellipsoidal particles, such calculations have a long history, dating back to early polymer-solution rheologists such as Simha and Kirkwood. Some of the history of early incorrect attempts to include such rotary Brownian effects is documented by Haber and Brenner (1984) in a paper addressed to calculating the 0(0) coefficient and normal stress coefficients for general triaxiai ellipsoidal particles in the case where the rotary Brownian motion is dominant over the shear (small rotary Peclet numbers)—a problem first resolved by Rallison (1978). 

Enrichment of Co(II) by early polymers thus would occur at Ej (L) > -0.47 V, that is, for almost all biologically relevant ligands other than thiolates. In considerable contrast with this, amino acids have E (L) -0.05 V while the corresponding value for peptides is about zero, oligocarboxylates ranging from about -0.13 V (malate) down to some -0.26 V (citrate). The difference in Ej (L) caused by chemical evolution thus will suffice to promote step 1 if the absolute value of E (L) of the educts is not higher than some h-0.2 V - provided... 

ROMP techniques have been used to prepare a family of monomers displaying a single saccharide residue. These hydrophilic monomers 22 have been polymerized under a variety of conditions. Early polymers were prepared by the use of ill-defined RuCI, catalysts. Recently, catalyst 9b was used under a variety of conditions to produce polymers for the required biological studies. Suspension conditions using DTAB as surfactant is required to obtain high molecular weight polymers 23 (Eq. 16). 

Common polymers such as polystyrene (PS) and polymethylmethacrylate (PMMA) have been used as gate dielectric materials [7,20,46]. Their ready availability made them some of the early polymers investigated by researchers in the field [11,39,47]. However, the low capacitances of these films made them less attractive than other polymers. Poly(4-methylstyrene) has been explored as a possible polarizable gate insulator [48]. 

One of the key contributions to early polymer-supported asymmetric phosphine development was made by Kagan and co-workers with their report in 1973 of polymer-supported DIOP 101 [DIOP = 2,3-0-isopropylidene-2,3-... 

Two of the early polymers described in Table 8.1 were melt spun into monofilament sutures, which exhibit the tensile properties shown in Table 8.3. 

Nylons were one of the early polymers developed by Carothers. Today, nylons are an important thermoplastic, with consumption in the United States of about 1.2 billion lb in 1997 88 Nylons, also known as polyamides, are synthesized by condensation polymerization methods, often an ahphatic diamine and a diacid. Nylon is a crystalline polymer with high modulus, strength, and impact properties, and low coefficient of friction and resistance to abrasion. Although the materials possess a wide range of properties, they all contain the amide (-CONH-) linkage in their backbone. Their general structure is shown in Fig. 2.8. 

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