Copolymer preparation

Figure 7.3 Fraction of nj sequences of the indicated length for copolymers prepared from equimolar feedstocks with rj r2 = 0.03 (shaded) and T1T2 = 0.30 (unshaded). [Data from C. Tosi, Fo/ym. 5ci. 5 451 (1968).]...

Table 7.5 Fraction of Mj Sequences of Length nj for Copolymers Prepared from Feedstocks of Different Composition for a System with rjr2 = 1...

The spectrum shown in Fig. 7.5 shows the appropriate portion of the spectrum for a copolymer prepared from a feedstock for which fj = 0.153 It turns out that each polyene produces a set of three bands The dyad is identified with the peaks at X = 298, 312, and 327 nm the triad, with X = 347 367, and 388 nm and the tetrad with X = 412 and 437 nm. Apparently one of the tetrad bands overlaps that of the triad and is not resolved. Likewise only one band (at 473 nm) is observed for the pentad. The identification ol these features can be confirmed with model compounds and the location and relative intensities of the peaks has been shown to be independent of copolymer composition. 

In this article the term acrylamide polymer refers to all polymers which contain acrylamide as a major constituent. Consequendy, acrylamide polymers include functionalized polymers prepared from polyacrylamide by postreaction and copolymers prepared by polymerizing acrylamide (2-propenamide, C H NO) with one or more comonomers. 

Copolymers are typically manufactured using weU-mixed continuous-stirred tank reactor (cstr) processes, where the lack of composition drift does not cause loss of transparency. SAN copolymers prepared in batch or continuous plug-flow processes, on the other hand, are typically hazy on account of composition drift. SAN copolymers with as Httle as 4% by wt difference in acrylonitrile composition are immiscible (44). SAN is extremely incompatible with PS as Httle as 50 ppm of PS contamination in SAN causes haze. Copolymers with over 30 wt % acrylonitrile are available and have good barrier properties. If the acrylonitrile content of the copolymer is increased to >40 wt %, the copolymer becomes ductile. These copolymers also constitute the rigid matrix phase of the ABS engineering plastics. 

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

Polymers of Styrene Derivatives. Many styrene derivatives have been synthesized and the corresponding polymers and copolymers prepared (61). Glass-transition temperatures for a series of substituted styrene polymers are shown in Table 3. The highest T is that of... 

Anionic Gopolymerization. Typical copolymers prepared by anionic copolymerization are shown ia equations 21—24 (30—32). 

Step-Growth Gopolymerization. A sample of a block copolymer prepared by condensation polymerisation is shown in equation 30 (37). In this process, a prepolymer diol (HO—Z—OH) is capped with isocyanate end groups and chain extended with a low molecular-weight diol (HO—E—OH) to give a so-called segmented block copolymer, containing polyurethane hard blocks and O—Z—O soft blocks. 

At the same time, however, considerable research was being done, especially in Germany, on a novel process called emulsion polymerization, in which the monomer was polymerized as an emulsion in the presence of water and soap. This seemed advantageous since the product appeared as a latex, just like natural mbber, leading to low viscosity even at high soHds content, while the presence of the water assured better temperature control. The final result, based mainly on work at the LG. Farbenindustrie (IGF) (10), was the development of a butadiene—styrene copolymer prepared by emulsion polymerization, the foremnner of the present-day leading synthetic mbber, SBR. 

In 1978 Hiils (Mumcu et al ) described the properties of a block copolymer prepared by condensation of polytetramethylene ether glycol with laurin lactam and decane-1,10-dicarboxylic acid. The materials were introduced as XR3808 and X4006. The polyamide XR3808 is reported to have a specific gravity of 1.02, a yield stress of 24 MPa, a modulus of elasticity of 300 MPa and an elongation of break of 360%. The Swiss company Emser Werke also introduced similar... 

The most important practical application of the organometallic complex photoinitiators is the possibility of using these types of initiators in modifying the pre-existing polymer chain, e.g., block, graft, and crosslinked copolymers preparation. 

Using the above method, Bamford and Han [59] have succeeded in synthesizing and characterizing copolymers in which each block is an alternating copolymer. The block copolymers prepared are of general structure ... 

Bowmer and Tonelli [161] have also studied the thermal characteristics of the whole range of ethylene-vinyl chloride copolymers prepared by partial reductive dechlorination of PVC using tri-n-butyltin-hydride. Naqvi [162] has substantiated further his explanations for the thermal stability characteristics of ethylene-vinyl chloride copolymers reported by Braun et al. [159] using the results of Bowmer and Tonelli [161] as a basis. 

The amount of the copolymer to be added into a binary blend depends on several factors. Since the copolymer preparation is an expensive process, it should be used to its maximum efficiency. The amount of copolymer (w) required to saturate a unit volume of blend is given by ... 

In this chapter techniques of block copolymer preparation involving thermally labile azo compounds are reviewed. Upon heating, aliphatic azo compounds evolve nitrogen thus forming two carbon centered free radicals. 

The epoxy-acrylic resin referred to above is a graft copolymer prepared by the polymerisation of acrylic monomers in the presence of the epoxy resin in such a way that grafting of the acrylic onto the epoxy takes place. Water dispersibility is achieved by neutralising carboxyl groups in the acrylic polymer chain with ammonia or amine. Amino or phenolic resins are used as crosslinkers. Alternatively, solvent-borne epoxy-amino or epoxy-phenolic lacquers can be used. 

Several wide-porous affinity and size-exclusion chromatographic supports were prepared by Ivanov, Zubov et al. by means of acylation of aminopropyl-glass supports by copolymers of N-vinyl pyrrolidone (N-VP,1) and acryloyl chloride (AC,2), M = 7700 and 35000 respectively [50, 51]. The copolymers prepared by free radical copolymerization contain their units almost in equimolar proportion, with high tendency to alternation expected from the copolymerization parameters (rj = 0.035, r2 = 0.15 [52]). Residual carbonyl chloride groups of the chemisorbed copolymer could be transformed to 2-hydroxyethylamides which were solely... 

While sequence distributions are usually subject to more experimental noise than composition data, this is often outweighed by the greater information content. In principle, reactivity ratios can be estimated from a single copolymer sample. The consistency in reactivity ratios estimated with eqs. 45 and 46 for copolymers prepared with different monomer feed compositions and/or obtaining the same result from cqs. 50 and 51 (4 aab—Ai ab) and cqs. 52 and 53 (r aba-Aiba) arc... 

Figure 7.4 Molecular weight distributions for HEA BA S copolymer prepared...

Table 9.9 Block Copolymers Prepared by Macromonomer RAFT Polymerization under Starved-Feed Conditions.380"595...

Table 9.28 Diblock Copolymers Prepared by RAFT Polymerization1...

Other block copolymers prepared using similar strategies include PEO (anionic) with second block poly(4-vinylpyridme).M ... 

In this section of our review, we shall discuss the morphological aspects and structure-property relationships of a few specific copolymeric systems which we think will represent the general features of siloxane containing multiphase copolymers. More detailed discussions about the properties of each copolymer system may be found in the references cited during our review of the copolymer preparation methods. On the other hand an in-depth discussion of the interesting surface morphology and the resultant surface properties of the siloxane containing copolymers and blends will be provided. 

Polyethylene, a thermoplastic, is the largest selling plastic material. LDPE is a branched polyethylene whose branches prevent close packing and gives low density. HDPE is polyethylene that has essentially no branching, so the molecules pack very well, which leads to high density and high crystallinity. LLDPE is actually a copolymer prepared at low temperature and low pressure from a mixture of ethylene and about 10% of a C4-C8 olefin. 

Horlbeck, G., Siesler, H. W., Tittle, B., and Trafara, G., Characterization of polyether and polyester homo- and copolymers prepared by ring-opening poljnnerization with a new catalytic system. Macromolecules. 10. 284-287, 1977. 

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