Poly molecular composites

Conducting polymer composites have also been formed by co-electrodeposition of matrix polymer during electrochemical polymerization. Because both components of the composite are deposited simultaneously, a homogenous film is obtained. This technique has been utilized for both neutral thermoplastics such as poly(vinyl chloride) (159), as well as for a large variety of polyelectrolytes (64—68, 159—165). When the matrix polymer is a polyelectrolyte, it serves as the dopant species for the conducting polymer, so there is an intimate mixing of the polymer chains and the system can be appropriately termed a molecular composite. 

The copolymers obtained for the P(DMA)-itat-(HPA) (Scheme 9) library revealed relatively low PDI values below 1.3 and increasing Mn,opc values with increasing HPA content, as listed in Tables. It should be noted that a poly(methyl methacrylate) (PMMA) calibration was used for the calculation of the Mn pc values and this causes an overestimation for HPA containing polymers. The copolymer compositions were calculated from the H NMR spectra however, this method was not suitable for reliable conversion determination since the DMA-C//3 groups overlap in the NMR spectra not only with the HPA-O// group but also with broad backbone signals, which obstruct any reliable integration. Therefore, elemental analysis was used as an alternative method for the calculation of the molecular composition of the copolymers. 

Xie D, Zhang C, Wu L (2009) Preparation of poly(propylene carbonate) molecular composite. Wuhan Ligong Daxue Xuebao 31 15-18... 

Microcellular foaming, bimodal cell size distributions, and high open-celled contents of molecular composites of HT-polymers were reported by Sun et al. [33], investigating blends of a rod-like polymer polybenzimidazole with an aminated PSU and poly(phenyl sulfone) by using carbon dioxide as a blowing agent. The complex foaming behavior was related to phase separation within the otherwise... 

It was noted also that satisfactory compatibilization could be achieved by local miscibility (given by solubility parameters) rather than direct matching of the chemical and macro-molecular composition. This may require the copolymer to have several components, such as poly(styrene-co-ethylene)-b-poly(butene-co-styrene) (SEES), which has been found useful in compatibilization of HDPE and PET (Bonner and Hope, 1993). 

Some recent examples demonstrating the molecular dispersion of rod polymer molecules in coil polymer matrices due to ionic interactions were given by Parker et al. (1996). These systems were based on three types of ionic PPTA s (Figure 5.4) and polar polymers, such as poly(4-vinylpyridine) (PVP), poly(vinyl chloride) (PVC), poly(ethylene oxide) (PEO), and poly(styrene-co-acrylonitrile) (S-AN). Due to the ionic-dipole interactions the rod-coil polymer pairs formed molecular composites as revealed by optical clarity, polarized microscopy, Tg measurements, as well as TEM observations. More significantly the molecular composites based on amorphous matrix polymers (e.g., PVP) were all transparent and showed no phase separation upon heating. Therefore they are melt-processible. As would expected, the mechanical properties of the molecular composites were... 

Recently, combinations of polymers meeting the basic concept of molecular composites have been reported. Poly-(p-phenylene terephthalamide) miscibility with PA-6 and PA-66 was reported [Kyu et al., 1989]. The blends were prepared by rapid coagulation of methane sulfonic acid solutions in water. Above 70% of the rigid rod polymer, polyamide crystallization disappears implying a level of intermixing of the blend constituents. However, thermal treatment results in phase separation thus indicating metastability for this combination. 

Thermoset molecular composites reported by Chuah etal. [1989] investigated poly(p-phenylene benzobisthiazole) reinforcement of bisbenzocy-clobutene (BCB) terminated imide oligomers. Samples were prepared via extrusion of a solution of the blend followed by coagulation. Samples were compression molded to advance the thermosetting constituent. Phase separation (domain size of 100-200 nm) occurred during coagulation... 

One of the basic problems confronting molecular composites is the difficulty of finding miscible combinations of rigid rod polymers with flexible chain polymers. Poly(p-phenylene benzobisthiazole)/poly(-2,5(6)-benzimidazole block copolymers have been reported by Tsai et al. [1985] and are noted to exhibit better processability and mechanical properties than the simple blends of the block copolymer constituents. Chang and Lee [1993] prepared poly(p-benzamide)/Pl block copolymers and reported on the liquid crystalline behavior. Such approaches would appear to have future implications. As an example PA e.g., PA-66) block copolymers with rigid rod polyamides could be prepared and used in blends with PA-66 to yield the desired molecular composite. 

It seems in Fig. 2g that all the experimental points are lying on a master surface, which is a first indication that there might be a physical law describing the correlation between the pore size and the molecular architecture of the amphiphile. However, because neither the one-phase nor the two-phase model was appropriate to describe the data (as shown elsewhere)," a new model was needed. It seems that in addition to the hydrophobic core (bright yellow), a certain fraction of the hydrophilic poly(ethylene oxide) (PEO) chain contributes to the size of the mesopore Dc (areas I and H in Fig. 3c). Only the remaining fraction of PEO is imbedded in the pore wall. By considering the total volume given by the number of units in the amphiphile chain and the stabilization of the interface I + II/III, it was finally possible to derive an equation that relates the mesopore size to the molecular composition of the amphiphile expressed as Vvb (see Eq. 1) ... 

Lauter, U., Meyer, W.H., Wegner, G., 1997. Molecular composites from rigid-rod poly(p-phenylene) s with oUgo (oxyethylene) side chains as novel polymer electrolytes. Macromolecules 30,2092-2101. 

Molecular composites as an extension of fiber reinforcement Molecular composites is designed to use rigid rodlike molecules as reinforcement for the flexible coil molecules as matrix. The patent applications on the molecular composites were made almost in the same age independently by Takayanagi in Japan in 1977 and by Helminiak in the United States in 1978. Takayanagi proposed thermoplastic nylon reinforced by poly(p-phenylene terephthalamide)(PPTA) and Helminiak proposed wet process using poly(p-phenylene benzobisthiazole)(PBT)-reinforced poly(2,5(6)benzimidazole) (ABPBI). In molecular composite (MC) [15,16,17], the fineness of reinforcement was pursued to its limit, i.e. to the molecular dimension. 

Crystallites may also be considered to act as reinforcing fillers. For example, the rubbery modulus of poly(vinyl chloride) was shown by lobst and Manson (1970,1972,1974) to be increased by an increase in crystallinity calculated moduli in the rubbery state agreed well with values predicted by equation (12.9). Halpin and Kardos (1972) have recently applied Tsai-Halpin composite theory to crystalline polymers with considerable success, and Kardos et al (1972) have used in situ crystallization of an organic filler to prepare and characterize a model composite system. More recently, the concept of so-called molecular composites —based on highly crystalline polymeric fibers arranged in a matrix of the same polymer—has stimulated a high level of experimental and theoretical interest (Halpin, 1975 Linden-meyer, 1975). 

Quite early solution blend work by Takayanagi et al. [83] of rigid aromatic polyamides (poly(p-phenylene terephthalate)) (PPTA) and flexible aliphatic polyamides, nylon 66 and nylon 6 (the latter will be discussed here) has been instrumental in developing the concept of molecular composites and although this lies more in the realm of lyotropic blends, it is often cited in the literature with regard to the effect of the PLC on the crystallization of other components in blends. PPTA has the structure... 

Baker, C.K., Y.J. Qiu, and J.R. Reynolds. 1991. Electrochemically induced charge and mass transport in polypyrrole/poly(styrenesulfonate) molecular composites. / Phys Chem 95 4446. 

The early work on properties of molecular composites was done by Hwang et al. (1983a, b). They performed experimental studies of solution processing of films based on poly(p-phenylene benzobisthiazole) with both poly(2,5 (6 ) benzimidazole (ABPBI) and poly(2,5 (6 ) benzothiazole) (ABPBT). The films were shown to possess very high modulus and strength values, which improve upon heat treatment. The uniaxial modulus of highly oriented molecular composites was shown to follow the linear rule of mixtures. 

Tsou et al. (1996) prepared molecular composites by dispersing rigid-rod molecules of ioiucally-modified poly(p-phenylene terephtalamide) in a polar poly (4-vinyl pyridine) (PVP) matrix. The mechanical properties of the molecular composite were found to increase with concentratimi and to attain maximum values at about 5 wt% of the PPTA anion. When specific interactions are not present, as in composites with nmi-anionic PPTA, the properties are significantly reduced compared to those of the PPTA anion/PVP composites. 

H. Akita, H. Kobayashi, Studies on molecular composite. IV. Block copolymer as a singlecomponent nano composite consisting of poly(p-phenylene benzobisthiazole) and thermoplastic aromatic polyamide. Polymer Journal 31 (10) (1999) 890-894. 

Miscibility, Structure, and Property of Poly (biphenyl dianhydride perfluoromethylbenzidine)—Poly(ether imide) Molecular Composites... 

One promising approach to producing a true molecular composite is to make rod and coil components thermodynamically miscible by introducing attractive interactions, such as hydrogen bonds (16-18), between them. This method has proven useful for enhancing miscibility in flexible-flexible blends. Even more useful (stronger) interactions may be ionic interactions, such as ion-ion and ion-dipole interactions various studies on ionomer blends have demonstrated that ionic interactions can enhance the miscibility of otherwise immiscible polymer pairs (79). Polymers studied include polystyrene, poly(ethyl acrylate), poly(ethyleneimine), nylon, and poly (ethylene oxide) (20-22). 

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