Crystalline polymers alcohol

The actual experimental moduli of the polymer materials are usually about only % of their theoretical values [1], while the calculated theoretical moduli of many polymer materials are comparable to that of metal or fiber reinforced composites, for instance, the crystalline polyethylene (PE) and polyvinyl alcohol have their calculated Young s moduli in the range of 200-300 GPa, surpassing the normal steel modulus of 200 GPa. This has been attributed to the limitations of the folded-chain structures, the disordered alignment of molecular chains, and other defects existing in crystalline polymers under normal processing conditions. 

In the case of crystalline polymers it may be that solvents can cause cracking by activity in the amorphous zone. Examples of this are benzene and toluene with polyethylene. In polyethylene, however, the greater problem is that known as environmental stress cracking , which occurs with materials such as soap, alcohols, surfactants and silicone oils. Many of these are highly polar materials which cause no swelling but are simply absorbed either into or on to the polymer. This appears to weaken the surface and allows cracks to propagate from minute flaws. 

Monolayers are best formed from water-insoluble molecules. This is expressed well by the title of Gaines s classic book Insoluble Monolayers at Liquid-Gas Interfaces [104]. Carboxylic acids (7-13 in Table 1, for example), sulfates, quaternary ammonium salts, alcohols, amides, and nitriles with carbon chains of 12 or longer meet this requirement well. Similarly, well-behaved monolayers have been formed from naturally occurring phospholipids (14-17 in Table 1, for example), as well as from their synthetic analogs (18,19 in Table 1, for example). More recently, polymerizable surfactants (1-4, 20, 21 in Table 1, for example) [55, 68, 72, 121], preformed polymers [68, 70, 72,122-127], liquid crystalline polymers [128], buckyballs [129, 130], gramicidin [131], and even silica beads [132] have been demonstrated to undergo monolayer formation on aqueous solutions. 

Ferulic acid, a phenolic acid that can be found in rapeseed cake, has been used in the synthesis of monomers for ADMET homo- and copolymerization with fatty acid-based a,co-dienes [139]. Homopolymerizations were performed in the presence of several ruthenium-based olefin metathesis catalysts (1 mol% and 80°C), although only C5, the Zhan catalyst, and catalyst M5i of the company Umicore were able to produce oligomers with Tgs around 7°C. The comonomers were prepared by epoxidation of methyl oleate and erucate followed by simultaneous ring opening and transesterification with allyl alcohol. Best results for the copolymerizations were obtained with the erucic acid-derived monomer, reaching a crystalline polymer (Tm — 24.9°C) with molecular weight over 13 kDa. 

Poly(vinyl) alcohol (PVA) is a semi-crystalline polymer, which is already widely used for various applications, either under the form of films or fibers. Compared to other polymers, as it is water-soluble at high temperature, it is easy to process from aqueous solutions. Carbon nanotubes can also be dispersed or solubilized in water via different functionalization approaches. It was quite natural for researchers to try to mix carbon nanotubes and PVA to improve the properties of the neat polymer. In this chapter, we will first examine the different methods that have been used to process CNT/PVA composites. The structures and the particular interaction between the polymer and the nanotube surface have been characterized in several works. Then we will consider the composite mechanical properties, which have been extensively investigated in the literature. Despite the number of publications in the field, we will see that a lot of work is still to be done for achieving the most of the exceptional reinforcement potential of carbon nanotubes. 

A three-dimensional crystalline polymer often can be described as a fringed micelle (chains packed as a sheaf of grain) or as a folded chain. Regions where the polymer chains exist in an ordered array are called crystalline domains. These crystalline domains in polymers are typically smaller than crystalline portions of smaller molecules. Furthermore, imperfections in polymer crystalline domains are more frequent, and one polymer chain may reside both within a crystalline domain and within amorphous regions. These connective chains are responsible for the toughness of a polymer. Sharp boundaries between the ordered (crystalline) and disordered (amorphous) portions are the exception but do occur in some instances such as with certain proteins, poly(vinyl alcohol), and certain cellulosic materials. Highly crystalline polymers exhibit... 

Studies on melt-formed samples showed that mechanical loss peaks a processes) occur above the glass transformation but below the melting point for various crystalline polymers. Such mechanical loss processes have been reported for linear polyethylene (two processes) 41), polypropylene (77), poly (vinyl alcohol) (77), and polytrifluoromonochloroethylene 37). These have been attributed to motion in or of the crystalline regions. For linear polyethylene a NMR broad-line narrowing process 65) and a T minimum 20) are also found in this temperature region. 

Polymeric nanocomposites are a class of relatively new materials with ample potential applications. Products with commercial applications appeared during the last decade [1], and much industrial and academic interest has been created. Reports on the manufacture of nanocomposites include those made with polyamides [2-5], polyolefins [6-9], polystyrene (PS) and PS copolymers [10, 11], ethylene vinyl alcohol [12-15], acrylics [16-18], polyesters [19, 20], polycarbonate [21, 22], liquid crystalline polymers [8, 23-25], fluoropolymers [26-28], thermoset resins [29-31], polyurethanes [32-37], ethylene-propylene oxide [38], vinyl carbazole [39, 40], polydiacethylene [41], and polyimides (Pis) [42], among others. 

As a result of the reactions that occur during free-radical polymerization, the reacting monomer)s) may be arranged in different ways on the polymer chain. Consequently, most free-radical polymerizations yield atactic polymers, which are noncrystaUine. However, in cases where the pendant group is small enough to fit into a crystalline lattice, crystalline polymers are formed — for example, poly(vinyl alcohol). Besides, if the monomer is symmetrical, free-radical polymerization may also yield crystalline polymers, e.g., polyethylene and polytetrafluoroethylene. 

Semi-crystalline polymers such as polyethylene are less affected by organic liquids, but nevertheless, the amorphous phase is susceptible to attack. Both alcohols and surface active agents can eventually lead to crack formation. Severe conditions are used for laboratory quality control tests of the... 

Takayanagi s first comparison between the predictions of his model and the observed mechanical behaviour covered a wide range of crystalline polymers, including polyethylene, polyvinyl alcohol, polytetra-fluoroethylene, polyamide, polyethylene oxide, polyo. ymethylene and polypropylene. Attempts were made to define relaxation processes as associated with either the crystalline regions or the non-crystalline regions, and in the former case specific molecular mechanisms were proposed, e.cj. a local twisting mode of molecular chains around their axes and a translational mode of molecular chains along their axes. 

Polyvinylidene chloride appears as a crystalline polymer excelling in chemical resistance and low permeability, but it is difficult to process and thermally unstable. Both homopolymers vinyl acetate and vinyl alcohol ap-... 

It is well-known that many polymers, synthetic and natural, form physical, thermoreversible aggregates in dilute solutions, whereas in moderately concentrated solutions gels can be formed. Examples are poly(vinyl chloride), polyacrylonitrile, poly(vinyl alcohol), atactic polystyrene, mixtures of syndiotactic and isotactic poly(methyl methacrylates), liquid crystalline polymers, gelatin, agarose, carrageenans etc. 

Linear increases in crystallinity with increasing MWNT concentration of a MWNT/poly(vinyl alcohol) (PVA) composite were observed in DSC melting endotherms. This suggested that each CNT had a discrete crystalline polymer layer associated with it, which was supported by evidence from SEM imaging [69]. Indeed, others have observed polymer... 

Electrical conductivity measurements have been reported on a wide range of polymers including carbon nanofibre reinforced HOPE [52], carbon black filled LDPE-ethylene methyl acrylate composites [28], carbon black filled HDPE [53], carbon black reinforced PP [27], talc filled PP [54], copper particle modified epoxy resins [55], epoxy and epoxy-haematite nanorod composites [56], polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blends [57], polyacrylonitrile based carbon fibre/PC composites [58], PC/MnCli composite films [59], titanocene polyester derivatives of terephthalic acid [60], lithium trifluoromethane sulfonamide doped PS-block-polyethylene oxide (PEO) copolymers [61], boron containing PVA derived ceramic organic semiconductors [62], sodium lanthanum tetrafluoride complexed with PEO [63], PC, acrylonitrile butadiene [64], blends of polyethylene dioxythiophene/ polystyrene sulfonate, PVC and PEO [65], EVA copolymer/carbon fibre conductive composites [66], carbon nanofibre modified thermotropic liquid crystalline polymers [67], PPY [68], PPY/PP/montmorillonite composites [69], carbon fibre reinforced PDMS-PPY composites [29], PANI [70], epoxy resin/PANI dodecylbenzene sulfonic acid blends [71], PANI/PA 6,6 composites [72], carbon fibre EVA composites [66], HDPE carbon fibre nanocomposites [52] and PPS [73]. 

Three poly(n-alkyl acrylates) PA-H, PA-16, PA-18 and two poly-(vinyl alcohol aliphatic acid esters) PVA-1A and PVA-16 have been synthesized. They are white crystalline polymers at room temperature, characterized with IR, DSC, SALLS-photometer and polarizing microscope. Only PA-I4 and PVA-IZf are effective for 0/ diesel oil. The influences of molecular weight, molecular weight distribution and amount of addition of PA-1i+ and PVA-lif upon the pour-point depression of oil are very alike. These results reveal the length of n-alkyl side-chain of the polyesters plays the most important role in depressing the pour-point of petrolic oil and the order of linking in the ester group seems in no relation to this effect. 

The novel partially crystalline polymer (3) with munber-average molecular weight (M ) of up to 5700 was prepared imder various conditions by catalyzed self-condensation of 3-hydroxypropyl methoxycarbonylethyl sulfide (4) or 3-hydrox5 ropyl carboxyethyl sulfide (5) (22). The degree of crystallinity, melting temperature (Tm and temperature of initial decomposition (Ta) were 36-46%, 37-47°C, —61 to —70°C, and 164-260°C, respectively. The monomers (4) and (5) were prepared by an addition of methyl 3-mercaptopropionate and 3-mercaptopropionic acid with allyl alcohol [107-18-6] catalyzed by AIBN [2,2 -azobis(2-methylpropionitrile), azobisisobutyronitrile, azodiisobutyro-dinitrile, 2,2 -azobis(2-methylpropanenitrile), a,a -azodiisobutyronitrile, 2,2 -azo-bis(isobut5T onitrile), 2,2 -dicyano-2,2 -azopropane, Porofor-57, 2,2 -dimethyl-2,2 -azodipropionitrile, 2,2(-azobis(2-methylpropionitrile))] [78-67-1]. 

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