Injectable polymers chemical structure

Some types of the polymers were investigated in detail. The photoconductivity of polyethylene with quantum efficiency 10 5-10 10 is caused by impurities, Schottky type contact injection, and hole transport [82,83], The crystallinity increase is accompanied by a photocurrent increase. There is no clear correlation between the chemical structure and the photocurrent. 

Biodegradable polymers are similar in terms of their chemical structure to conventional thermoplastics such as polyethylene, polypropylene and polystyrene. They can be processed using standard polymer processing methods such as film extrusion, injection moulding and blow moulding. 

Finally, the most likely value of x in the CPs of interest here is about 2.5 eV or less. Therefore, an ohmic contact for electrons should have a work function of at most 3 eV. This is the case for the alkali metals from Li (2.9 eV) to Cs (2.15 eV) these elements are also, for the same reason, good n-dopants of the CPs slight diffusion into the polymer may then generate an n+ contact favorable for electron injection. The most widely used low-work-function cathode in CP EL is, however, Ca (2.9 eV) [269]. One could try to increase x by a proper choice of the monomer chemical structure, but unless one succeeds in avoiding having Eg reduced simultaneously, the emission will be shifted to the red part of the spectrum. 

Shape memory polymers make up another class of injectable biomaterials for vascular applications, yet are relatively new in the field of endovascular embolization. Shape memory polymers are chemically structured so that they are able to reversibly take on a different physical shape in response to some stimuli (Small et al, 2007). Usually these different shapes include a compact form and an expanded form of the polymer. In the case of endovascular embolization, the expanded polymer can be pre-formed to fit specific contours of an individual aneurysm (Ortega et al, 2007). Upon interacting with some type of stimuli, such as heat or cold, the material is compacted into a shape that can be delivered through a microcatheter. The process of using shape memory polymers to embolize an aneurysm is shown in Fig. 7.5, along with samples of expanded SMPs (Ortega et al, 2007). 

Thus,the relationship between the modulus of as-spun fibers and the modulus of injection molded test pieces is not clear,but the flexural modulus is depending upon the BB mol% of polyarylates and the BB mol% might be used as the parameter of the rigidity of polymer chains.We observed many plate-like fibrils and a few needle like fibrils on the cross section of the flexural fractured test pieces of Me-HQ/BB/Cl-PEC(m/n=9/l).Then we prepared TLCPs with more rigid chemical structure,Me-HQ/BB/Cl-PEC(m/n=9.5/0.5),which showed a similar flexural modulus of 39 GPa as Me-HQ/BB/Cl-PEC(m/n 9/l),but X-ray diffraction pattens and SEM of these 2 polymers were quite different.The injection molded test pieces of Me-HQ/BB/Cl-PEC(m/n-9.5/0.5) showed lower degree of orientation and fewer fibrils than those of m/n=9/l as shown in Fig.7 and8(8). 

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