Single-component polymers

There are several ways in which to incorporate nlo groups chemically into a polymer structure. The approach that has been used most widely is to bond the nlo groups to a saturated carbon backbone via a flexible aliphatic spacer (Fig. 4.5), forming side-chain polymers. In this way, the backbone confers polymeric handling properties and the side-group nlo properties, whole the flexible spacer allows freedom for the side-groups to be reorientated by an electric field for poling. 

There have been two main approaches to this target system. 

Side-groups with suitable polymerizable functional ends can first 

Vinyl addition has been widely used to produce nlo single-component side-chain polymers. The commercial potential for nlo polymers has meant that industrial research groups are reticent to publish full synthesis routes or polymer compositions, preferring to use code names. This makes the task of objective study of the latest literature difficult. 

AIBN-initiated addition polymerization has also been used to prepare a variety of nitrophenoxyazo and nitrophenoxystilbene dyes terminated with a vinyl function. The nlo dyes were copolymerized with mesogenic 

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Fig. 10.60 Compressive stress-strain behavior of PS and LLDPE at 25°C and crosshead speed of 25.4 mm/min. At a compressive stress level of 20 MPa the deformation of the soft LLDPE is large, in the dissipative region and nearly twenty times the PS deformation, which is of the order of 0.04, in the elastic nondissipative range. [Reprinted by permission from B. Qian, D. B. Todd, and C. G. Gogos, Plastic Energy Dissipation (PED) and its Role in Heating/Melting of Single Component Polymers and Multi-component Polymer Blends, Adv. Polym. Techn., 22, 85-95 (2003).]...

B. Qian, D. B. Todd, and C. G. Gogos, Plastic Energy Dissipation and its Role on Heating/ Melting of Single-component Polymers and Multi-component Polymer Blends, Adv. Polym. Technol., 22, 85-95 (2003). 

The above result seems to adequately describe the observed Brillouin scattering of a homogeneous single-component-polymer fluid near its glass transition (13). If a binary mixture is truly homogeneous, then Equation 11 also should be valid for this case. However, if the two components phase separate, then the distribution function given by Equation 10 is invalid and further analysis is required. 

The design of single-component polymer transport materials continues to interest researchers in this field. The use of such materials will completely eliminate solvent extraction, diffusional instability, and crystallization of the small molecules. One obvious route that has not been successful to date is the design of yet another aromatic-amine-containing carbon-backbone polymer. An alternative may be to explore the large class of glassy silicon-backbone polymers, such as polysilylenes (14) and polyphosphazenes (iS). 

Tsai ML, Liu C Y, Hsu M A and Chaw T J, White fight emission from single component polymers fabricated by spin coating, Appl. Phys. Lett. 82 (2003) 550-552. 

The automotive industry started to use plastics in 1946. Since then, its content steadily increases (see Figure 16.4). Today, the plastics for automotive apphcations are dominated by polymer alloys, blends, and composites. The reason for it is the need for automotive parts to show a wide range of performance characteristics that are virtually impossible to meet using a single-component polymer. Thus, for example, in Saturn, front fenders and rear quarter panels are from PA/PPE, door outer skins are from PC/ABS, the bumper fascias are TPO, etc. 

As noted earlier, there are now many hundreds, indeed thousands, of polymer blends in use or that have been described in the literature. The present section has merely given a few examples. It should also be remembered that even polymers often thought of as being single-component polymers are often blends, indeed all polymers are blends of molecules with different molar masses. More importantly, most polyethylenes (PEs) are blends. Those that are simply blends of different grades of PE to meet particular requirements for density or other properties, or are blends of PE with up to 15 wt% of other polymers to modify properties, are generally described simply as polyethylenes. Only those blends of PE with larger concentrations of a second polymer are usually described as blends. 

Wang, Y. Bansal, V. Zelikin, A.N. Caruso, F. Templated synthesis of single-component polymer capsules and their application in drug delivery. Nano Lett. 2008, 8 (6), 1741-1745. 

In 2008, Qian et al. synthesized two series of four-arm and eleven-arm star polystyrene with six different molar masses for each case. They determined surface tension of single component polymer film using a Wilhelmy plate technique... 

Just as topographic features can be used to control dewetting in single component polymer films, such templates also can be used to control polymer blend and block copolymer phase segregation. A difficulty with BCPs, however, is generating a template with sufficiently small feature sizes to match the natural phase separation... 

Tadmor, Z. and Gogos, C.G. (2006) Principles of Polymer Processing, 2nd edn, John Wiley Sons, Inc., Hoboken, NJ. Qian, B., Todd, D.B., and Gogos, C.G. (2003) Plastic energy dissipation and its role in heating/melting of single component polymers and... 

Demand for high performance plastics that are suitable to replace conventional materials has helped drive the development of polymer blending processes and techniques. Complementary to this, there is an increasingly strong desire for inexpensive plastics that meet the demands of specific products or applications by combining the properties of multiple single-component polymers. 

The morphology of polymer blends in bulk systems has been extensively studied because of the wide range of applications of polymeric materials owing to the improved mechanical and thermal characteristics compared with single component polymers. However, there are few reports on 2-dimensional morphology for polymer blend and its phase-separated structures. 

Miscible blends will be expected to exhibit rheological behavior similar to single component polymers. One of the simplest equations applied to miscible systems involves the relationship ... 

By varying the composition of a blend, the engineer hopes to obtain a gradation in properties that might be tailored for specific applications. This is true for miscible polymer pairs such as polyphenylene oxide and polystyrene that appear and behave as single-component polymers. 

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