Chemistry Reference
In-Depth Information
Thermoplastic, light-stable polyurethanes derived from caprolactone polyesters
and diamines have been prepared by interfacial polycondensation of diamines with
polyester diol bis(chloroformate)s. The effects of varying the molecular weight of
the polyester diol and varying the diol initiator, as well as of methyl substituents on
the caprolactone rings used to prepare the polyester, and of the diamine structure,
have been determined. The polyester diol bis(chloroformate)s were prepared by
ring-opening of e-caprolactone or methyl e-caprolactone in the presence of 1,4-
butanediol, 1,3-butanediol, 2-butene-1,4-diol, trimethylolpropane monoallyl ether,
or neopentyl glycol, followed by phosgenation [256].
A phosgene-free process for preparing urethane and carbonate monomers and poly-
mers has been reported [257]. The process involves reaction of CO
2
with amines
(e.g. 4,4
0
-methylenebis(cyclohexylamine)), alcohols, or amino alcohols in the pres-
ence of an amidine- or guanidine-type base (e.g. N-cyclohexyl-N
0
,N
0
,N
00
,N
00
-tetra-
ethylguanidine), followed by treatment of the resulting ammonium carbamate or
carbonate salt with a primary or secondary hydrocarbyl halide of a specified struc-
ture in a polar, aprotic solvent (e.g. N-methylpyrrolidinone). When hydrocarbyl
dihalides or -polyhalides are used in the second step, polyurethanes and polycar-
bonates are formed.
5.4.2
Polyketones, Polyureas
Besides the aforementioned urethane polymers, phosgene may also be used to
prepare polymers via the C
O linkage, such as polyketones, polyureas, etc. For ex-
ample, the preparation of aromatic polyether-polyketones by a two-stage Friedel-
Crafts polycondensation has been reported. A monomer system comprising an
aromatic dicarboxylic acid chloride (or phosgene)/polynuclear arene mixture or a
polynuclear aromatic carboxylic acid chloride containing a hydrogen atom amen-
able to electrophilic substitution is mixed with a Lewis acid, a Lewis base (op-
tional), and an inert solvent. The mixture is partially polymerized in a first reaction
zone, and then passed through a second reaction zone along with an inert solvent
or an inert gas-saturated inert solvent to complete the polymerization without
fouling of the polymerization reactor. This method has been used for the poly-
merization of terephthaloyl chloride with 4,4
0
-diphenoxybenzophenone [258]. A
poly(arylene ether ketone) is prepared by polymerizing a polynuclear aromatic
monomer bearing both an acid halide function and an active hydrogen atom, or by
co-polymerizing phosgene or an aromatic diacid dihalide with a polynuclear aro-
matic monomer having two active hydrogen atoms, in the presence of a Lewis acid
and, optionally, a controlling agent (especially a Lewis base) and/or a non-protic
diluent. A thermally stable, linear polymer is obtained, which has a high molecular
weight and is largely free of pendant groups resulting from ortho-substitution of
para-linked aromatic rings in the polymer backbone [259].
A process for the preparation of aryl polyether-polyketones by electrophilic
polymerization has been disclosed [260]. The polymers, having excellent high-
temperature resistance, are prepared by the reaction of carboxylic acid halides in
b
