Equimolar copolymers

General Copolymerization Studies. DHA-4VP System. In order to examine the copolymerizability of DHA with 4VP and to investigate some properties of the copolymer, equimolar amounts of DHA and 4VP were copolymerized in 2-propanol at 70°C. The powdery, off-white, purified polymer was soluble in DMF, slightly soluble in chloroform, and insoluble in water and tetrahydrofuran (THF). In contrast, poly(4VP) was soluble in THF, DMF, and chloroform. 

Table 2 Influence of the polymerization conditions on M of various copolymers (equimolar amounts of donor and acceptor monomers).

Similarly, a-methylstyrene, 24, and p-methoxystyrene, 25 can be copolymerized with 1 (R = H or CH3) producing copolymers, 26 and 27, reported to have alternating monomer sequence, 26 (Eqs. 6.3.3 and 6.3.4) [62]. In each instance copolymer equimolar in the two monomers is obtained. Its formation has been attributed to a charge-transfer interaction. 

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).]...

The radical-catalyzed polymerization of furan and maleic anhydride has been reported to yield a 1 1 furan-maleic anhydride copolymer (89,91). The stmcture of the equimolar product, as shown by nmr analyses, is that of an unsaturated alternating copolymer (18) arising through homopolymerization of the intermediate excited donor—acceptor complex (91,92). 

The equimolar copolymer of ethylene and tetrafluoroethylene is isomeric with poly(vinyhdene fluoride) but has a higher melting point (16,17) and a lower dielectric loss (18,19) (see Fluorine compounds, organic-poly(VINYLIDENE fluoride)). A copolymer with the degree of alternation of about 0.88 was used to study the stmcture (20). Its unit cell was determined by x-ray diffraction. Despite irregularities in the chain stmcture and low crystallinity, a unit cell and stmcture was derived that gave a calculated crystalline density of 1.9 g/cm. The unit cell is befleved to be orthorhombic or monoclinic (a = 0.96 nm, b = 0.925 nm, c = 0.50 nm 7 = 96%. 

Alternating equimolar copolymers of vinyl acetate and ethylene and alternating copolymers of vinyl acetate and acrylonitrile have been reported (127,128). Vinyl acetate and certain copolymers can be produced directly as films on certain metallic substrates by electroinitiation processes in which the substrate functions as one electrode (129). 

Random copolymers can be synthesized by step-giowth copolymeiization in an equimolar mixture of four monomers (1). 

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... 

Morphology of the anionically synthesized triblock copolymers of polyfp-methyl-styrene) and PDMS and their derivatives obtained by the selective chlorination of the hard segments were investigated by TEM 146). Samples with low PDMS content (12%) showed spherical domains of PDMS in a poly(p-methylstyrene) matrix. Samples with nearly equimolar composition showed a continuous lamellar morphology. In both cases the domain structure was very fine, indicating sharp interfaces. Domain sizes were estimated to be of the order of 50-300 A. 

Other hand, when an equimolar mixture of 2,5-DSP and l OEt is recrystallized from benzene, yellow crystals, comprising 2,5-DSP and l OEt in a molar ratio of 1 2, deposit. In the DSC curve of this crystal, a single endothermic peak is observed at 166°C, which is different from the melting point of either 2,5-DSP (223°C) or l OEt (156°C). Furthermore, the X-ray powder diffraction pattern of the crystal is quite different from those of the homocrystals 2,5-DSP and l OEt. Upon irradiation the cocrystal 2,5-DSP-l OEt affords a crystalline polymer (77i h = 1.0 dl g in trifluoroacetic acid). The nmr spectrum of the polymer coincides perfectly with that of a 1 2 mixture of poly-2,5-DSP and poly-1 OEt. In the dimer, only 2,5-DSP-dimer and l OEt-dimer are detected by hplc analysis, but the corresponding cross-dimer consisting of 2,5-DSP and l OEt is not detected at all (Hasegawa et al., 1993). These observations by nmr and hplc indicate that the photoproduct obtained from the cocrystal 2,5-DSP-l OEt is not a copolymer but a mixture of poly-2,5-DSP and poly-l OEt in the ratio 1 2. 

The polymerization rates of styrene and acrylonitrile monomer are not equal. If we were to initiate polymerization in an equimolar solution of the two monomers, the styrene monomer would initially be depleted at a faster rate than the acrylonitrile. Thus, the copolymer molecules initially produced would contain a higher concentration of styrene than acrylonitrile. As the reaction progressed, the styrene would be depleted from the solution and the comonomer ratio in the copolymer would gradually shift towards a higher acrylonitrile content. The final product would consist of polymer chains with a range of comonomer compositions, not all... 

The NMR spectrum of the copolymer prepared from an equimolar mixture of the monomers is shown in Figure 10. In this spectrum, five well separated regions of NMR peaks were observed. The assignments of the peaks (Table III) were made by using the existing spectral information on homopolymers of 1-hexene and 5-methyl-1,4-hexadiene as well as the intensity variations among the copolymers with different monomer charge ratios. 

Figure 10. 300 MHz IH-NMR spectrum of a deuterobenzene solution of an equimolar copolymer of 5-methyl-l,4-hexadiene and 1-hexene prepared with a EttAlCl/ S-TiCl, catalyst at 0°C in pentane solvent.

MHz - H-tWR SPECTRAL DATA OF AN EQUIMOLAR COPOLYMER OF 1-HEXENE AND 5-METHYL-1,4-HEXADIENE... 

The formation of inter- and intrapolymer complexes has also been shown to affect the polymerization kinetics. For example, Ferguson and Shah (1968) investigated the influence of intrapolymer complexation on the kinetics of AA in the presence of copolymer matrices composed of either A-vinylpyrrolidone and acrylamide or A--vi nyl pyrrol idone and styrene. The polymerization rate reaches a maximum in the vicinity of AA to VP ratio equal to one for the VP/AAm matrix. This maximum in the polymerization rate is most pronounced in the presence of copolymer with the highest content of VP. When the hydrophilic acrylamide is replaced with the more hydrophobic styrene monomer in the copolymer matrix, the observed maximum in AA polymerization rate occurred at a lower than equimolar ratio of AA to VP. The hydrophilic groups of VP were interacting with the hydrophobic nucleus consisting of the styrene units in the VP/St copolymer, and were thus unable to participate in the formation of the complex unlike in the case of VP/AAm copolymer matrix. 

Thioetherification of PECH is feasibly performed in DA-solvents as already described in the patent (20J. For example, the highest substitution was obtained by the reaction of P(ECH-EO)(1 1 copolymer of epichloro-hydrin and ethylene oxide) and equimolar thiophenoxide in HMPA at 100°C for 10 h as DS 83% for sodium and 93% for potassium salts. The DS in our nucleophilic substitution was estimated by the elemental analysis as well as the titration of liberated chloride ion with mercuric nitrate (21). In the latter method, reacted medium was pretreated with hydrogen peroxide when the reductive nucleophiles which can react with mercuric ion were used. As described before for PVC, thiolation was also achieved conveniently with iso-thiuronium salt followed by alkaline hydrolysis without the direct use of ill-smelling thiolate. The thiolated PECH obtained are rubbery solids, soluble in toluene, methylene chloride, ethyl methyl ketone and DMF and insoluble in water, acetone, dioxane and methanol. 

Considerable effort has been carried out by different groups in the preparation of amphiphihc block copolymers based on polyfethylene oxide) PEO and an ahphatic polyester. A common approach relies upon the use of preformed co- hydroxy PEO as macroinitiator precursors [51, 70]. Actually, the anionic ROP of ethylene oxide is readily initiated by alcohol molecules activated by potassium hydroxide in catalytic amounts. The equimolar reaction of the PEO hydroxy end group (s) with triethyl aluminum yields a macroinitiator that, according to the coordination-insertion mechanism previously discussed (see Sect. 2.1), is highly active in the eCL and LA polymerization. This strategy allows one to prepare di- or triblock copolymers depending on the functionality of the PEO macroinitiator (Scheme 13a,b). Diblock copolymers have also been successfully prepared by sequential addition of the cyclic ether (EO) and lactone monomers using tetraphenylporphynato aluminum alkoxides or chloride as the initiator [69]. 

In a similar way, the grafting-from technique has been applied to the synthesis of poly(chloroethylvinylether) chains by grafted PCL segments, i.e., po-ly(CEVE-g-CL) graft copolymers. Purposely cationically prepared PCEVE were partially modified by the introduction of 5-10% hydroxyl groups [79]. An equimolar reaction of the pendant hydroxyl functions with HAI/BU2 provided diisobutyl aluminum monoalkoxides dispersed along the polyether backbone. 

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... 

Phosphazene copolymers have also been prepared by the thermolysis of equimolar mixtures of the phenyl/alkyl and dialkyl substituted P-trifluoroethoxy-phosphinimines. 

Unfortunately, we have found no way to estimate the relative amounts of 1,4 and 1,2-coupled units in these polymers. There are however some curious features of the results obtained with copolymers which suggest the operation of unusual select vities in the polymerization reactions. For example, the copolymer resulting from polymerization of equimolar 4-bromo-2,6-dichlorophe-noxide and 2,4,6-trichlorophenoxide (Mr, > 50,000) gave both an... 

If equimolar quantities of Mi and M2 are used in an azeotropic copolymerization, what is the composition of the feed after 50% of the copolymer has formed ... 

What will be the composition of copolymers produced in the first part of the polymerization of equimolar quantities of vinylidene chloride and vinyl chloride ... 

What is the composition of the first copolymer chains produced by the copol5Tnerization of equimolar quantities of styrene and methyl methacrylate in (a) free radical, (b) cationic, and (c) anionic copolymerization ... 

What is the composition of the first copolymer butyl rubber chains produced form equimolar quantities of the two monomers ... 

The copolymer described by Eq. 6-1, referred to as a statistical copolymer, has a distribution of the two monomer units along the copolymer chain that follows some statistical law, for example, Bemoullian (zero-order Markov) or first- or second-order Markov. Copolymers formed via Bemoullian processes have the two monomer units distributed randomly and are referred to as random copolymers. The reader is cautioned that the distinction between the terms statistical and random, recommended by IUPAC [IUPAC, 1991, in press], has often not been followed in the literature. Most references use the term random copolymer independent of the type of statistical process involved in synthesizing the copolymer. There are three other types of copolymer structures—alternating, block, and graft. The alternating copolymer contains the two monomer units in equimolar amounts in a regular alternating distribution ... 

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