Novel block copolymers including acrylonitrile sequences and sequences including units derived from glutarimide units and processes for preparing same

There is disclosed novel block copolymers formed of acrylonitrile sequences and sequences containing at least about 50 mole percent of acrylamide units and at most about 50 of units selected from the group consisting of carboxyl, ester, amide, hydrazide and hydroxylamide units and formed by reacting a block copolymer having acrylonitrile sequences and sequences of glutarimide units with a low molecular weight compound having a functional group selected from the group consisting of hydroxyl, primary amino, secondary amino, hydrazo and hydroxylamino group. The reaction is effected at a pH of about 7.5 and higher, preferably in the presence of a solvent and/or swelling agent.

FIELD OF INVENTION 
This invention relates to novel block copolymers including acrylonitrile 
sequences, and more particularly to novel block copolymers comprised of 
acrylonitrile sequences and sequences including as a major portion units 
derived from glutarimide units and processes for preparing same. 
BACKGROUND OF THE INVENTION 
In copending application U.S. Ser. No. 188,224 filed Sept. 17, 1980 
allowed, there are disclosed novel block copolymers compositions comprised 
of acrylonitrile sequences and sequences of glutarimide units of a 
molecular weight of from about 10,000 to about 2,000,000 where the 
acrylonitrile sequences and sequences including glutarimide units are of a 
molecular weight of at least about 400 with the number of sequences being 
at least about 2 and preferably 5 and higher. The resulting block 
copolymers are relatively stable with regard to acids even at elected 
temperatures, but are reactive to basic materials. 
OBJECTS OF THE INVENTION 
An object of the present invention is to provide novel block copolymers. 
Another object of the present invention is to provide novel block 
copolymers having acrylonitrile sequences and sequences including units 
derived from glutarimide units. 
Still another object of the present invention is to provide novel block 
copolymers having acrylonitrile sequences and sequences including units 
derived from glutarimide units yielding swellable but water insoluable 
hydrogels. 
Still another object of the present invention is to provide novel processes 
for preparing such novel block copolymers. 
SUMMARY OF THE INVENTION 
These and other objects of the present invention are achieved by reacting a 
block copolymer having acrylonitrile sequences and sequences of 
glutarimide units with a low molecular weight compound having a functional 
group selected from the group consisting of hydroxyl, primary amino, 
secondary amino, hydrazo and hydroxylamino group, and to form novel block 
copolymers having acylonitrile sequences and sequences containing at least 
about 50 mole percent of acrylamide units and at most about 50 of units 
selected from the group consisting of carboxyl, ester, amide, hydrazide 
and hydroxylamide units. The reaction is effected at a pH of about 7.5 and 
higher, preferably in the presence of a solvent and/or swelling agent. 
BRIEF DESCRIPTION OF THE INVENTION 
As described in the aforementioned copending application (P/12245), the 
precursor block copolymers are comprised of acrylonitrile sequences and 
sequences including glutarimide units and of a molecular weight of from 
about 10,000 to about 2,000,000 where the acrylonitrile sequences and 
sequences including glutarmide units are of a molecular weight of at least 
40 with the number of sequences being at least about 2 and preferably 5 
and higher. Such block copolymers essentially a two phase structure with 
an acrylonitrile and glutarimide domains wherein the acrylonitrile and the 
glutarimide domains exhibit an amorphous structure. 
An acrylonitrile sequence is a continuous sequence of acrylonitrile units 
of a molecular weight of at least about 400, and preferably of at least 
about 600. The sequences including a major portion of glutarimide units is 
a continuous sequence having a molecular weight of at least about 400 and 
preferably at least about 750. The number of sequences per polymer chain 
is at least 2 and perferable from 5 or more. 
The novel block copolymer compositions of the present invention are readily 
prepared by treating the precursor block copolymers having acrylonitrile 
sequences and sequences comprised of a major portion of glutarimide units 
with a low molecular weight compound having a functional group selected 
from the group consisting of hydroxyl, primary amino, secondary amino, 
hydrazo and hydroxylamino group at a temperature of from about 0.degree. 
to about 185.degree. C., preferably of from 15.degree. to 65.degree. C. to 
form block copolymers having acrylonitrile sequences and sequences 
containing at least about 50 mole percent acrylamide units and at most 
about 50 mole percent of units selected from the group consisting of 
carboxyl, ester, amide, hydrazide and hydroxylamide units. 
The reaction is effected at a pH of 7.5 or greater, preferable in the 
presence of a solvent and/or swelling agent for the precursor block 
copolymer. Reaction times are from about 1 to 600 minutes, preferable 10 
to 120 minutes. 
The reactions are carried out under mild conditions at which the -CN groups 
are not reactive thereby resulting in novel block copolymers wherein the 
acrylonitrile sequences thereof are of like acrylonitrile sequences of the 
precursor block copolymer. Thus, the glutarimide units are converted to 
acrylamide and units selected from the group consisting of carboxyl, 
ester, amide, hydrazide and hydroxylamide units with the result that the 
flexible portion of the precursor block copolymer is convered to a major 
portion of hydrophobic groups i.e. effectively a hydrogel multiblock 
copolymer. An essential feature of the block copolymers of the present 
invention is that at least one acrylamide unit is in a closest vicinity to 
the aforementioned other units. 
The conversion of the hydrophobic block copolymers into hydrogels permits 
utilization thereof by the attendant shape charge when in contact with 
water, such as: 
1. Forming hydrogel layers on hydrophobic blocks copolymers for use to 
decrease drag in tubes, on propellers of ships, and for forming slippery 
layers on catheters, sound and other medical devices. 
2. Sealing sand or soil by introducing powdered precursor block copolymer 
into such a substrat and thereafter converting the block copolymer to 
hydrogel particles by adding an alkali thereto. 
3. Incorporating highly reactive groups into hydrogels where such reactive 
groups are effective in immobilizing enzymes. 
The properties of the novel block copolymers are preselectable by varying 
the mole percent of acrylonitrile units to glutarimide units of the 
precursor block copolymers as well as by varying the number and the 
molecular weight of the sequences. 
Recovery of the block copolymers of the present invention may be effected 
in a plurality of ways depending on the reaction system in which the novel 
block copolymers are formed. If the alkali is sufficiently volatile, the 
block copolymer is recovered by evaporation of the alkali, such as 
ammonia. The block copolymers are readily extracted from the reaction 
systems with a liquid miscible therewith but immiscible with the dissolved 
block copolymers. Such miscible liquids include water, aqueous solutions, 
low aliphatic alcohols, ketones, glycols and the like. The block 
copolymers may be recovered by neutralization of the alkali.

EXAMPLES OF THE INVENTION 
The following examples are illustrative of conditions for the process of 
the present invention and it is to be understood that the scope of the 
invention is not to be limited thereby. 
EXAMPLE I 
A multiblock acrylonitrile-glutarimide-acrylamide copolymer of the 
following composition: 57.4 percent by weight of acrylonitrile units 
arranged into the sequences with average molecular weight of about 
1,500,33.2 percent by weight of glutarimide units and 9.4 percent by 
weight of acrylamide units arranged randomly into sequences with an 
average molecular weight of 1110, is admixed with an excess of 
2-animoethanol and maintained at 20.degree. C. After several hours, the 
resulting swollen mass is filtered and washed with methanol and had the 
following composition: 61 mole percent of acrylonitrile units, 9.8 mole 
percent of acrylamide units and 29.2 mole percent of 
2-hydroxyl-ethyl-N-acrylamide. The resulting block copolymer is a water 
swellable multiblock hydrogel showing the typical x-ray pattern of 
polyacrylonitrile with an amorphous halo. 
EXAMPLE II 
A solution of multiblock acrylonitrile-glutarimide-acrylamide copolymer of 
the following composition: 57.4 percent by weight of acrylonitrile units 
arranged into sequences with average molecular weight of about 1,500,33.2 
percent by weight of glutarimide units and 9.4 percent by weight of 
acrylamide units arranged randomly into sequences with an average 
molecular weight of 1110, is heated to 75.degree. C. and bubbled with dry 
air to remove HCl whereupon gaseous ammonia is introduced at a partial 
pressure of 1.2 atmospheres for two hours. The solution is subjected to 
air bubbling at ambient pressure and thereafter coagulated with water and 
formed an acrylonitrile-acrylamide hydrogel comprised of 61.8 mole percent 
acrylonitrile and 38.2 mole percent acrylamide. Thus illustrated a method 
of eliminating carboxylic groups from an acrylonitrile-acrylamide-acrylic 
acid hydrogel. 
EXAMPLE III 
A solution of a multiblock acrylonitrile-glutarimide-acrylamide copolymer 
of the following composition: 57.4 percent by weight of acrylonitrile 
units arranged into the sequences with average molecular weight of about 
1,500,33.2 percent by weight of glutarimide units and 9.4 percent by 
weight of acrylamide units arranged randomly into sequences with an 
average molecular weight of 1110, is heated to 75.degree. C. and bubbled 
with dry air to remove HCl whereupon gaseous dimethylamine is introduced 
for a period of 6 hours with the solution being maintained at a 
temperature of 30.degree. C. The resulting block copolymer is comprised of 
62 mole percent of acrylonitrile, 8.7 mole percent acrylamide and 29.3 
mole percent of N,N-dimethylacrylamide. 
EXAMPLE IV 
Polyacrylonitrile (M.W.=875,000) is dissolved in an aqueous solution of 
sodium rhodanide and sodium hydroxide (60 percent by weight and 5 percent 
by weight, respectively). The polymer solution is heated to 75.degree. C. 
until the polymer gelled (turned to dark red-brown) and then redissolved 
(honey-yellow color). The thus formed copolymer is precipitated by water 
and is a highly swellable multiblock copolymer (about 97 percent by weight 
of water) consisting of 11 mole percent of acrylonitrile, 52 mole percent 
of acrylamide and 37 mole percent of sodium acrylate. The solution is 
cooled and extruded into water to form a membrane about 0.5 mm. thick in a 
swollen state. The swollen membrane is washed and exposed on one side to a 
10 percent nitric acid solution. 
The membrane contracted as whole (the sodium acrylate is converted into 
acrylic acid) and a skin of yellow, turbid, non-swellable polymer about 
0.1 mm. thick is formed on the exposed side. Analysis of the skin revealed 
a multiblock copolymers of acrylonitrile-glutarimide-acrylamide (19.7 mole 
percent acrylonitrile; 66.8 mole percent of glutarimide; 13.4 mole percent 
of acrylamide; 0.1 mole percent of acrylic acid) with an average molecular 
weight of the acrylonitrile sequences of 550. The membrane is fixed in a 
frame and dried. 
The membrane is treated with an alcoholic solution of hexamethylene diamine 
whereby hydrophobic layer is cross-linked with free amino groups with 
concomitant increase in swelling capacity. The presence of free amino 
groups are convenient for bonding various active compounds, such as 
enzymes. 
Numerous modifications and variations of the present invention are possible 
in light of the above teachings and, therefore, within the scope of the 
appended claims, the invention may be practiced otherwise than as 
particularly described.