TMCS

A decisive breakthrough to a T range above 230°C was achieved with a polycarbonate based on spitobisiudan (SBI-PC, (8)) (203) or 3,3,5-trimethyl cyclohexane (TMC-PC, (7) whereia the cyclohexane ring bears three methyl groups) (204). 

The neady symmetrical composition of SBI-PC (T = 230° C) makes birefringence disappear iu homopolymers, but the material becomes very britde due to the blocking of the free rotation of the aromatic rings, which puts its technical appHcation iu question. Only a copolymerization with 80 wt BPA-PC reaches sufficient levels of impact resistance but T is lowered to 170°C and birefringence iucreases to 80% of that of BPA-PC (195,196). In contrast, TMC-PC as a homopolymer already has sufficient impact resistance at a T of 238°C and a birefringence of 83% of that of BPA-PC (195,205) (Table 7). 

Table 7. Properties of TMC-Polycarbonate and its Copolymers with BPA-Polycarbonate ...

Fig. 26. Qualitative compatison of substrate materials for optical disks (187) An = birefringence IS = impact strength BM = bending modulus HDT = heat distortion temperature Met = metallizability WA = water absorption Proc = processibility. The materials are bisphenol A—polycarbonate (BPA-PC), copolymer (20 80) of BPA-PC and trimethylcyclohexane—polycarbonate (TMC-PC), poly(methyl methacrylate) (PMMA), uv-curable cross-linked polymer (uv-DM), cycHc polyolefins (CPO), and, for comparison, glass.

TMS triflate [27607-77-8] is an extremely powerful sdylating agent for most active hydrogens. It surpasses the sdylating potential of TMCS by a factor of nearly 10. It readily converts 1,2- and 1,3-diketones into disilylated dienes (7). 

Cehte or firebrick packing for glc columns is often treated with TMCS, DMCS, or other volatile silylating agents (see Table 1) to reduce tailing by polar organic compounds. A chemically bonded methyl siUcone support is stable for temperature programming to 390°C and allows elution of hydrocarbons up to C q (20). 

Another approach is to copolymerise bis-phenol A with the bis-phenol of trimethylcyclohexanone (bis-phenol TMC) commercial materials were introduced in 1992. 

The TMC polycarbonate homopolymer has a glass transition temperature of 238°C, nearly 100°C above that of the bis-phenol A polycarbonate. Therefore, copolymers will have intermediate glass transitions depending on the relative proportions of TMC and bis-phenol A. Commercial grades (marketed by Bayer as Apec HT) have Vicat softening points from 158 to... 

Procedure. Treat 10 mg of sucrose with 1 mL of anhydrous pyridine, 0.2 mL of HMDS, and 0.1 mL of TMCS in the plastic-stoppered vial (or similar container). Shake the mixture vigorously for about 30 seconds and allow it to stand for 10 min at room temperature if the carbohydrate appears to remain insoluble... 

Another, and less surprising, example of ruthenium(IV) lies in the oxo complexes with macrocycles like 14-TMC (Figure 1.53). 

Potential Usage of TMC-Based Copolymers in Tissue Engineering.232... 

The cylindrical porous scaffolds based on TMC-DLLA copolymers were prepared by salt-leaching method. Two-ply porous nerve guides were prepared by a combination of dip-coating (inner layer) and fiber-winding (outer layer) techniques. 

In contrast to TMC-DLLA, the mechanical properties at equilibrium water uptake of TMC-CL copolymers are not significantly different from those in the dry state as shown in Table 8.1. 

Like the in vitro studies, the in vivo degradation of the TMC-CL copolymers containing 89% CL showed no change in shape or size after one year. As the degradation of the TMC-CL copolymers was so slow, a mature fibrous capsule remained throughout the year. Histological results of the TMC-CL copolymers were similar to those obtained from TMC-DLLA or other commonly used biodegradable polymers. 

Potential Usage oe TMC-Based Copolymers in Tissue Engineering 8.5.4.1 TMC-DLLA Copolymers in Heart Tissue Engineering... 

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