Copolymerization ceiling temperature

With most common monomers, the rate of the reverse reaction (depropagation) is negligible at typical polymerization temperatures. However, monomers with alkyl groups in the a-position have lower ceiling temperatures than monosubstituted monomers (Table 4.10). For MMA at temperatures <100 °C, the value of is <0.01 (Figure 4.4). AMS has a ceiling temperature of <30 °C and is not readily polymerizable by radical methods. This monomer can, however, be copolymerized successfully (Section 7.3.1.4). 

Propagation reactions in radical polymerization and copolymerization arc generally highly exothermic and can be assumed to be irreversible. Exceptions to this general rule arc those involving monomers with low ceiling temperatures (Section 4.5.1). The thermodynamics of copolymerization has been reviewed by Sawada.85... 

Copolymerizations of other monomers may also be subject to similar effects given sufficiently high reaction temperatures (at or near their ceiling temperatures - Section 4.5.1). The depropagation of methacrylate esters becomes measurable at temperatures >100 °C (Section 4.5.1).96 O Driseoll and Gasparro86 have reported on the copolymerization of MMA with S at 250 °C. 

In the copolymerization of isopropenylferrocene with a-methyl-styrene at 0°C, using varying molar ratios of isopropenylferrocene and a-methylstyrene, traces of polymer formation were obtained only at a 30/70 ratio of the two monomers, as shown in the data in Table III. Because a-methylstyrene has a much lower ceiling temperature than styrene, we also decided to use styrene as a comonomer under conditions similar to those employed with a-methylstyrene. The reaction temperature for the copolymerization with a-methylstyrene was 20°C. 

An interesting feature of the styrene-S02 system, —which indeed is true of all SO2 copolymerizations with comonomers capable of homopolymerizing—, is the existence of a ceiling temperature above which the formation of alternating units, SMS, is forbidden. The number fraction of M sequences of length n is... 

Aldehyde Copolymer Self Developing Electron-beam Resists. The ceiling temperature for the copolymerization of aliphatic aldehydes is usually below 0°C and the copolymers are easily depolymerized into monomeric aldehydes above 150°C under vacuum. This depolymerization into monomers also occurs on electron-beam or X-ray exposure as evidenced by combined gas-liquid partition chromatography-mass spectrometry. As a result, the copolymers of aldehydes behaved as self-developing positive resists and almost complete development was accomplished without any solvent treatment. Electron-beam exposure characteristics of the aliphatic aldehyde copolymers studied here are... 

Polymerization of captodative olefins is seen to be a potentially wide area of interest in polymer chemistry. Contrary to impressions in the literature, such olefins can homo- and copolymerize to high molecular weight polymers. Results to the contrary can be explained in terms of excessive steric hindrance by large electron-donating substituents, which should lead to slow propagation rates and low ceiling temperatures. 

A typical example showing that we are able to build macromolecules at will is given by C. P. Pinazzi and co-workers in the first chapter of the second section, Chapter 27. They report how model polyenes can be built and how they react. In Chapter 28 K. F. O Driscoll illustrates the limitations in polymerization. For every vinyl monomer, a ceiling temperature exists, above which depropagation exceeds polymerization. If two vinyl monomers are copolymerized at a temperature at which one depropa-gates, the polymer formed will have an unusual composition and sequence distribution. 

For every vinyl monomer there exists a ceiling temperature above which it is thermodynamically impossible to convert monomer into high polymer because of the depropagation reaction. If two vinyl monomers are copolymerized under conditions such that one or both may depropagate, the resultant polymer will have an unusual composition and sequence distribution. Existing theoretical and experimental works are reviewed which treat of copolymer composition, rate of copolymerization, and degree of copolymerization. 

Copolymerization is characterized by a ceiling temperature of 64°C. above which no polymerization takes place. 

The copolymerization must be conducted below the ceiling temperature. Isopropyl percarbonate (IPP) has been chosen because of its... 

A major limitation of a-methylstyrene in free-radical polymerizations is its very low ceiling temperature of 61 °C.347 As a result, AMS is utilized commercially only in radical copolymerization. Nonetheless, it is among the most active CCT monomers with Cc = 9 x 105 at 50 °C for 9a as CCT catalyst.348 This value is relatively unchanged at 40 °C. This high value reflects the low kp = 1.7 M 1 s 1 so that kc = 5 x 105 M-1 s 1. 

H5P, an a-methylstyrene derivative, seems to have a low ceiling temperature and consequently did not homopolymerize but underwent copolymerization with styrene, methyl methacrylate, and n-butyl acrylate. Based on the homopolymerization attempts, it appears that 2H5P is present as isolated monomer units in these copolymers. The co-polymerization parameters of 2H5V and 2H5P with styrene, methyl methacrylate, and n-butyl acrylate have also been determined. The results are shown in Figure 3 The copolymerization experiments were done to 5 conversions. 

Melt copolymerization requires high temperatures (T > 200 °C). In spite of the six-membered ring it has the extrapolated ceiling temperature T = 1800 °K, well above the decomposition temperature 43). Polyglycolide (mp = 224-226 °C) is converted into multifilament yam by usual melt-spinning and -drawing procedures giving products with tenacities (5-10 g/den) close to polyethyleneterephtalate fibres. 

The copolymerization of BCMO with THF above its ceiling temperature will be examined. The more reactive THF forms alternating copolymer only above 60 mol % content of THF in the mixture. At lower THF concentrations BCMO-BCMO dyads are also formed 33). 

The use of poly(olefin sulfones) in resist applications was first demonstrated by Bowden and Thompson at Bell lahoratories. They prepared them hy radical copolymerization of (liquid) SO2 with a whole range of olefins, at reaction temperatures deliberately kept low because of the low ceiling temperatures of poly(afk-ene sulfones). For poly(butene sulfone), Tc 64°C. The resulting copolymers possess a regular 1 1 alternating composition. 

The ceiling temperature for the copolymerization of sulfur dioxide with various vinyl compounds is shown in Table I [17] and is said to follow the relationship ... 

Olefins with electron withdrawing substituents (—CN, —COOH, —COOR) cannot enter into copolymerization with sulfur dioxide. The reactivities of the olefins with sulfur dioxide is obtained by using cyclohexene as a standard at — 20°C, far below the ceiling temperature where depropagation is negligible [18]. 

In a similar manner vinyl f-butyl carbonate copolymerizes with SO2 [61b]. Vinyl f-butyl carbonate and vinyl acetate have the same ceiling temperature ( —20°C), as was observed in the VAc/SOa copolymerization. No polymer is obtained above this temperature and the yield of polymers increases as the temperature is lowered to — 80°C (85% yield). 

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