Polycarbonate polysulfone block copolymers

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

The more certain approach leading to products in which the different component species must necessarily alternate along the chain is that involving the combination of two oligomers having mutually reactive end groups such that each species can react only with the other (equation 7). This procedure, which has been used particularly in recent work on polycarbonate-polysulfone and polysiloxane-polysulfone block copolymers, yields multiblock products with structures defined... 

The oligomer molecular weights were characterized by both UV-visible spectra (20, 21) and/or potentiometric titrations (22, 23). Details of the measurements are provided in these papers. The block copolymers also were characterized by intrinsic viscosity and in some cases by membrane osmometry and gel permeation chromatography. Additional characterization studies are continuing and will be reported later. A typical synthesis of a 5000-5000 polysulfone-S-polycarbonate-A copolymer via interfaciar polymerization is described below. 

Figure 3. High-temperature mechanical behavior of bis-A-polysulfone/bis-A-polycarbonate (16,000/17,000) block copolymer. Compression molded at 260°C.

Figure 8. Dynamic mechanical spectrum at higher temperatures for bis-S-polysulfone/bis-A-polycarbonate (10,000/10,000) block copolymer...

Two-phase, yet optically transparent, glass-glassy block copolymers can be produced from polycarbonate and polysulfone oligomers either by increasing average block weight beyond 16,000 g/mol or by increasing... 

Figure 11. DSC thermogram for bis-T-polysulfone/bis-A-polycarbonate (10,000/10,000) block copolymer. Heating rate, 40 K/min. Range, 5 meal/sec. (A) After annealing at 573 K (300° C) for 30 min. (B) Dried polymer powder, no thermal pretreatment.

Th-FFF can be applied to almost all kinds of synthetic polymers, like polystyrene, polyolefins, polybutadiene, poly(methyl methacrylate), polyisoprene, polysulfone, polycarbonate, nitrocelluloses and even block copolymers [114,194,220]. For some polymers like polyolefins, with a small thermal diffusion coefficient, high temperature Th-FFF has to be applied [221]. Similarly, hydrophilic polymers in water are rarely characterized by Th-FFF, due to the lack of a significant thermal diffusion (exceptions so far poly(ethylene oxide), poly(vi-nyl pyrrolidone) and poly(styrene sulfonate)) [222]. Thus Th-FFF has evolved as a technique for separating synthetic polymers in organic solvents [194]. More recently, both aqueous and non-aqueous particle suspensions, along with mixtures of polymers and particles, have been shown to be separable [215]. 

By the process shown in Reaction 17, block copolymers have been constructed with hard blocks derived from polysulfones, polycarbonates, poly(BPA-terephthalates), etc. 

Several classes of polymeric materials are found to perform adequately for blood processing, including cellulose and cellulose esters, polyamides, polysulfone, and some acrylic and polycarbonate copolymers. However, commercial cellulose, used for the first membranes in the late 1940 s, remains the principal material in which hemodialysis membranes are made. Membranes are obtained by casting or spinning a dope mixture of cellulose dissolved in cuprammonium solution or by deacetylating cellulose acetate hollow fibers [121]. However, polycarbonate-polyether (PC-PE) block copolymers, in which the ratio between hydrophobic PC and hydrophilic PE blocks can be varied to modulate the mechanical properties as well as the diffusivity and permeability of the membrane, compete with cellulose in the hemodialysis market. 

Commercial membranes for CO2 removal are polymer based, and the materials of choice are cellulose acetate, polyimides, polyamides, polysulfone, polycarbonates, and polyeth-erimide [12]. The most tested and used material is cellulose acetate, although polyimide has also some potential in certain CO2 removal applications. The properties of polyimides and other polymers can be modified to enhance the performance of the membrane. For instance, polyimide membranes were initially used for hydrogen recovery, but they were then modified for CO2 removal [13]. Cellulose acetate membranes were initially developed for reverse osmosis [14], and now they are the most popular CO2 removal membrane. To overcome state-of-the-art membranes for CO2 separation, new polymers, copolymers, block copolymers, blends and nanocomposites (mixed matrix membranes) have been developed [15-22]. However, many of them have failed during application because of different reasons (expensive materials, weak mechanical and chemical stability, etc.). 

Bosnyak, et (3) have prepared copolymers of poly(bisphenol-A-terephthalate) and bisphenol-A-poly-carbonate. These randomly coupled block or segmented copolymers are shown schematically in Equation 1. These materials deformed uniformly in tension, in contrast to homo-bisphenol-A polycarbonate where necking is observed (3). Block copolymers of bisphenol-A polycarbonates and bisphenol-A polysulfone have been investigated by McGrath, et al. (4,5,12). 

Other elastomer blends of commercial utility have been cited in the literature [96-98]. Polyolefin blends have been utilized in many forms to achieve modifications yielding environmental stress rupture resistance and to improve impact strength, flexibility, and filler acceptance [99,100]. The addition of ethylene-propylene rubber (EPR) or blends of EPR and high-density PE to PP has been specifically utilized for improving the low-temperature impact strength [101]. Low-modulus materials can be produced from EPR-PP blends containing more than 50% of EPR. These products include those under the trade names TPR, Somel, and Telcar [102-105]. Addition of rubber inclusion has been shown to yield definite improvements in the environmental stress rupture resistance [106]. Other examples of commercial rubber-based blends are impact-PS, ABS and bisphenol A polycarbonate blends and polysulfone blends made of a block copolymer of polysulfone and nylon 6 [107]. 

---