Polycarbonates propylene oxide with

CO2 and epoxides are polymerised into polycarbonates in the presence of zinc-based catalysts (e.g. ZnEy combined with water, tert-butylcatechol or pyrogallol (benzene with three -OH groups). For example, the polymerisation of propylene oxide with COj produces poly(propylene carbonate) (PPC), as shown in Figure 9.2. 

Propylene oxide can be copolymerized with other epoxides, such as ethylene oxide (qv) (25,29,30) or tetrahydrofiiran (31,32) to produce copolymer polyols. Copolymerization with anhydrides (33) or CO2 (34) results in polyesters and polycarbonates (qv), respectively. 

Carbon dioxide can itself be used as a feedstock as well as a solvent for the synthesis of aliphatic polycarbonates by precipitation polymerization. Propylene oxide [39] and 1,2-cyclohexene oxide [40] can both be polymerized with CO2 using a heterogeneous zinc catalyst (Scheme 10.21). 

Carbon dioxide is one of the most abundant carbon resources on earth. It reacts with an epoxide to give either a cyclic carbonate or a polycarbonate depending on the substrates and reaction conditions. Kinetic resolution of racemic propylene oxide is reported in the formation of both cyclic carbonate and polycarbonate. The fe ei value defined as ln[l-(conversion)(l+%ee)]/ln[l-(conversion)(l% ee)] reached 6.4 or 5.6 by using a Co(OTs)-salen complex with tetrabutylammonium chloride under neat propylene oxide or using a combination of a Co-salen complex and a chiral DMAP derivative in dichloromethane, respectively. 

Co(OAr)-salen complex [Ar = 2,4-(N02)2CeH3] with tetrabutylammonium chloride under neat propylene oxide, quite similar to the conditions for the cyclic carbonate synthesis, give polycarbonate with fe ei of 3.5. ° Without any additives, the use of Co(OAc)-salen provides the polycaronate with fe ei of 2.8. ... 

Table 6.2 shows the important applications of sodium hydroxide. Direct applications can be further broken down into pulp and paper (24%), soaps and detergents (10%), alumina (6%), petroleum (7%), textiles (5%), water treatment (5%), and miscellaneous (43%). Organic chemicals manufactured with sodium hydroxide are propylene oxide (23%), polycarbonate (5%), ethyleneamines (3%), epoxy resins (3%), and miscellaneous (66%). Inorganic chemicals manufactured are sodium and calcium hypochlorite (24%), sodium cyanide (10%), sulfur compounds (14%), and miscellaneous (52%). As you can see from the number of applications listed, and still the high percentages of miscellaneous uses, sodium hydroxide has a very diverse use profile. It is the chief industrial alkali. 

Polymeric nanocomposites are a class of relatively new materials with ample potential applications. Products with commercial applications appeared during the last decade [1], and much industrial and academic interest has been created. Reports on the manufacture of nanocomposites include those made with polyamides [2-5], polyolefins [6-9], polystyrene (PS) and PS copolymers [10, 11], ethylene vinyl alcohol [12-15], acrylics [16-18], polyesters [19, 20], polycarbonate [21, 22], liquid crystalline polymers [8, 23-25], fluoropolymers [26-28], thermoset resins [29-31], polyurethanes [32-37], ethylene-propylene oxide [38], vinyl carbazole [39, 40], polydiacethylene [41], and polyimides (Pis) [42], among others. 

These procedures for investigating blends can be combined with the chain-dynamics techniques presented in Sec. III.D. Addition of polycarbonate to a poly(hexaneamide)/poly(propylene oxide) blend hardens the material this has been attributed to restrictions in the mobility of the amine nitrogen in the polyamide caused by interfacial interactions among the other blend components [242]. The solid-state heteronuclear WISE (wzdeline 5cparation) experiment can be tailored to selectively highlight the interface... 

The development of catalysts based on transition metals by Ziegler and Natta [11] allowed the development of stereospecific propylene polymerization processes and ethylene polymerization in the 1950s. Several process schemes were developed at that time, of which some are still in use. The major problem in process development has been to deal with the heat of polymerization, an issue that was solved, for example, by using an inert solvent as a heat sink or by flashing of monomer followed by condensation outside the reactor. In the same period, polycarbonate and (somewhat later) poly(propylene oxide) (PPO) were developed. The main characteristic of the polymers developed so far was that they were bulk materials, to be produced in extremely large quantities. 

Because CO2 is a nontoxic, nonflammable, and inexpensive substance, there is continued interest in its activation with transition metal complexes and its subsequent use as a Cl feedstock (1,2). Even though CO2 is used to make commodity chemicals such as urea, salicylic acid and metal carbonates, efficient catalyst systems that exploit this feedstock as a comonomer in polymerization reactions have been elusive (3,4). One reaction that has been considerably successful is that of CO2 with epoxides to yield aliphatic polycarbonates (Scheme 1) (5). Of particular significance is the synthesis of poly(propylene carbonate) (PPC), because the starting materials—propylene oxide (PO) and CO2—are inexpensive. 

A few examples of polymerization reactions catalyzed by MOFs are reported [161]. Zn carboxylate [162] was shown to catalyze the polymerization of propylene with CO to polycarbonates (M = 75,000g/mol). Alkoxylation of propylene glycol or acrylic acid with ethylene/propylene oxide resulted in polyols. Radical polymerization of divinylbenzene was performed using [M Cbdcj CtedjJ (M=Cu, Zn) [163-165]. 

Even more complex are compositions that are physical mixtures of polymers. One important outlet for ABS resins is in blends (alloys) with other polymers such as nylons or polycarbonates. Polystyrene itself is blended with poly(propylene oxide). In each case, the blend can be tougher than constituent resins. Often these blends offer advantages of lower cost and easier fabrication. 

---