CN107163282A - Macroporous polymer resin of fast temperature response and preparation method thereof - Google Patents

Abstract

The invention provides a method for preparing a polymer macroporous resin with rapid temperature response, which comprises the following steps: under acidic conditions, under the action of an initiator, a hydrophilic temperature-sensitive monomer is grafted with polyvinyl acetal foam reaction to obtain a polymer macroporous resin with rapid temperature response; the hydrophilic thermosensitive monomer is any one of N-isopropylacrylamide, N-ethylacrylamide and N,N-diethylacrylamide one or more. The present invention uses oxidation-reduction to initiate polymerization, and for the first time introduces a polymer chain segment with temperature sensitivity into the macroporous polyvinyl formal precursor, and the obtained material maintains the unique interconnected structure of the polyvinyl formal foam material itself. The pore structure ensures that the resulting material can reach swelling equilibrium in just a few minutes at low temperature, and it only takes a few minutes to reach deswelling equilibrium at high temperature.

Description

Polymer macroporous resin with rapid temperature response and preparation method thereof

technical field

The invention relates to the technical field of polymers, in particular to a polymer macroporous resin with rapid temperature response and a preparation method thereof.

Background technique

In recent years, with the development of synthesis technology, a large number of smart materials, such as: shape memory materials, self-healing materials, and stimuli-responsive (optical, electrical, thermal, magnetic) materials have been designed and reported. Due to the diversity of structural design and chemical composition, polymer-based smart materials have always been a research hotspot and have attracted extensive attention of researchers. Among them, the most prominent are polymer materials with temperature response, which can be used as drug release materials, tissue engineering materials, gene release materials, etc.

Temperature-responsive polymer material refers to the behavior that its solution state will show a volume phase transition (Volume Phase Transition) at a certain temperature during the temperature change process. High critical solution temperature (UCST) polymers, and polymers that show immiscibility with increasing temperature are called low critical solution temperature (LCST) polymers. Among them, temperature-sensitive polymers with low critical solution temperature (LCST) have been widely studied in the past ten years. Many polymers, such as poly(isopropylacrylamide) (PNIPAAm), polyvinylcaprolactam (PVCL), and poly(N,N-diethylacrylamide) (PDEAAM), exhibit LCST phenomena in aqueous solutions. Taking PNIPAAm as an example, because it has a phase transition temperature (~33°C) close to the physiological temperature of the human body (~36.5°C), it is the most deeply studied temperature-sensitive material so far. Its volume phase transition around 32°C was first reported by Tanaka et al. When the outside temperature is lower than LCST, the hydrophilic groups N-H and C=O in PNIPAAm form hydrogen bonds with water molecules, and the polymer chains generate solvent When the external temperature rises above the LCST of PNIPAAm, the hydrophilic N-H and C=O groups form intramolecular hydrogen bonds, and the hydrophobic polymer chains shrink, drain and aggregate in water, and further from The water settles out. In general, the inclusion of hydrophilic components in thermosensitive gels can reduce the hydrophobic interactions between its molecular chains, leading to an increase in the phase transition temperature, while the introduction of hydrophobic components can lead to a decrease in the phase transition temperature. Such structural properties make thermosensitive hydrogels such as PINPAAm have broad application prospects in biomedicine, such as drug release and artificial organ muscles.

However, when the external temperature is higher than the LCST, the traditional PNIPAAm gel will form a dense skin layer (Dense skin layer) on its outer surface during the phase transition process to limit the outward diffusion of water molecules inside the gel; and when the temperature is low During LCST, the dense skin layer formed will also restrict the entry of external water molecules, making PNIPAAm show a significant response hysteresis to external temperature changes. At the same time, the vitrification phenomenon of the polymer chain during shrinkage will also make it respond The rate becomes slow, which largely limits its application in the actual process.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a polymer macroporous resin with rapid temperature response and a preparation method thereof, and the prepared polymer macroporous resin has a rapid temperature response characteristic.

The invention provides a kind of preparation method of the polymer macroporous resin of rapid temperature response, comprises the following steps:

Under acidic conditions, under the action of an initiator, the hydrophilic temperature-sensitive monomer and polyvinyl acetal foam undergo a graft reaction to obtain a polymer macroporous resin with rapid temperature response;

The hydrophilic thermosensitive monomer is any one or more of N-isopropylacrylamide, N-ethylacrylamide and N,N-diethylacrylamide.

The present invention uses polyvinyl acetal foam as a raw material, and any one or more of N-isopropylacrylamide, N-ethylacrylamide and N,N-diethylacrylamide as temperature-sensitive monomers , the prepared polymer macroporous resin retains the unique open-pore structure of polyvinyl acetal foam, which makes the water molecules in the network of the material easy to diffuse when the external temperature changes, ensuring that the material has the characteristics of rapid temperature response.

The preparation method provided by the present invention is carried out under acidic conditions, and the acidic conditions are preferably any one of sulfuric acid aqueous solution, hydrochloric acid aqueous solution and phosphoric acid aqueous solution, or a mixture of multiple solutions.

Preferably, the acid concentration of the acidic condition is 0.01-1M.

The initiator of the grafting reaction is a water-soluble organic-inorganic redox initiation system, wherein the oxidant is preferably any one or more of manganese pyrophosphate, ammonium cerium nitrate, ammonium cerium sulfate and cerium perchlorate, and the reduction The agent is the polyvinyl acetal foam itself.

The concentration of the oxidizing agent is preferably 0.001-0.5M.

The hydrophilic thermosensitive monomer is preferably any one or more of N-isopropylacrylamide, N-ethylacrylamide and N,N-diethylacrylamide.

The concentration of the hydrophilic thermosensitive monomer is preferably 1-5M.

The molar ratio of the hydrophilic thermosensitive monomer to the grafting sites in the polyvinyl acetal foam is preferably (2.5-20):1.

The temperature of the grafting reaction is preferably 0-70°C, and the reaction time is preferably 6-72h.

In some specific embodiments of the present invention, the raw materials for the grafting reaction also include hydrophilic monomers, preferably acrylamide, methacrylamide and N-methylolacrylamide any one or more of them.

That is, under acidic conditions, under the action of an initiator, the mixture of the hydrophilic temperature-sensitive monomer and the hydrophilic monomer is grafted with polyvinyl acetal foam to obtain a polymer macroporous resin with rapid temperature response.

The existence of the above-mentioned hydrophilic segment can effectively improve the hydrophilicity of the obtained sample, and at the same time, it can also effectively increase its swelling degree below the LCST, and realize a larger temperature response characteristic of the material.

The molar mass ratio of the hydrophilic monomer to the grafting site in the polyvinyl formal foam is (2.5-20):1, preferably 10:1.

In the present invention, said M represents mol/L.

In the present invention, the graft polymerization is initiated by oxidation-reduction, and the temperature-sensitive segment is introduced into the polyvinyl acetal foam base to endow the material with temperature-responsive characteristics, and at the same time, the open-cell structure of the polyvinyl acetal foam material is still maintained after modification , the modified polyvinyl acetal foam material finally prepared has the characteristic of rapid temperature response, and the preparation process is simple.

The present invention also provides a polymer macroporous resin with rapid temperature response, which is prepared according to the above preparation method.

The pore size and distribution of the fast temperature-responsive polymer macroporous resin were measured by mercury intrusion porosimetry, and the results showed that the pore size was 2-200 μm, and the pore size was concentrated at 90 μm. At low temperature (20°C), the dry sample can reach water saturation within 3 minutes; at high temperature (48°C), the sample saturated with water at low temperature can reach dehydration equilibrium within 1 minute.

Compared with the prior art, the present invention provides a method for preparing a polymer macroporous resin with rapid temperature response, comprising the following steps: under acidic conditions, under the action of an initiator, a hydrophilic thermosensitive monomer and polyethylene Alcohol acetal foam undergoes grafting reaction to obtain polymer macroporous resin with rapid temperature response;

The hydrophilic thermosensitive monomer is any one or more of N-isopropylacrylamide, N-ethylacrylamide and N,N-diethylacrylamide.

The present invention uses oxidation-reduction to initiate polymerization, and for the first time introduces a polymer chain segment with temperature sensitivity into the macroporous polyvinyl formal precursor, and the obtained material maintains the unique interconnected structure of the polyvinyl formal foam material itself. The pore structure ensures that the resulting material can reach swelling equilibrium in just a few minutes at low temperature, and it only takes a few minutes to reach deswelling equilibrium at high temperature. Compared with traditional temperature-sensitive hydrogels, which take several hours or even days to reach the equilibrium of swelling and deswelling, the material shows an extremely fast response rate; and compared with most of the current reports in the literature using physical and chemical methods Compared with the temperature-sensitive hydrogel, the bulk polyvinyl acetal-based macroporous temperature-sensitive material prepared by the present invention has the characteristics of uniform pore size distribution and faster water absorption rate, and at the same time, its preparation method has mild reaction conditions and the method It is simple and easy to operate, and the preparation cycle is short, so it is easy to scale up the preparation.

detailed description

In order to further illustrate the present invention, the polymer macroporous resin with rapid temperature response provided by the present invention and its preparation method are described in detail below in conjunction with examples.

Example 1

Add 1500mL 0.01M hydrochloric acid solution, 50g polyvinyl acetal foam material, 0.2mol cerium perchlorate, and 7mol N-isopropylacrylamide (NIPAAm) into a 2500mL two-necked flask, seal it, and react at 0°C for 70h. After taking it out, it is washed with distilled water to neutrality, and dried in a vacuum oven to constant weight to obtain polyvinyl acetal foam grafted with poly-N-isopropylacrylamide.

The temperature responsiveness of the obtained material is characterized by the difference in water absorption rate at low temperature and high temperature, and the detection method is as follows:

Low-temperature water absorption rate: Accurately weigh a certain amount of the foam material (A) obtained above, soak it in low-temperature (20°C) distilled water for 3 minutes, take out the water on the filter for 30 seconds, and weigh it (B). The liquid absorption ratio of the foam material is calculated by the following formula: liquid absorption ratio=(B-A)/A. This process was repeated three times, and the average value of the measurements was taken as the water absorption capacity.

Water absorption rate at high temperature: Soak the sample after the above test in distilled water at a higher temperature (60°C) for 3 minutes, and measure its water absorption rate at high temperature according to the above method.

Take 0.1 g of the polyvinyl alcohol-based macroporous material grafted with polyisopropylacrylamide prepared above, and measure its absorption rate of distilled water at low temperature and high temperature according to the methods described above. At low temperature, the time to reach saturated absorption and the absorption rate are 3min and 45g/g respectively; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 2.5min and 20g/g, respectively.

Example 2

In a 2500mL two-necked flask, add 0.02M hydrochloric acid solution, 50g polyvinyl acetal foam material, 0.3mol cerium perchlorate, 1mol N-isopropylacrylamide and 6mol acrylamide, seal it, react at 10°C for 60h, and take out the sample Afterwards, it is washed with distilled water to neutrality, and dried in a vacuum oven to constant weight to obtain a polyvinyl acetal foam of graft copolymerization of poly-N-isopropylacrylamide and polyacrylamide.

Take 0.1 g of the obtained polyvinyl alcohol-based thermosensitive macroporous material, and measure its absorption rate for distilled water at low temperature and high temperature respectively according to the method described above. At low temperature, the time to reach saturated absorption and the absorption rate are 4min and 52g/g respectively; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 3min and 35g/g, respectively.

Example 3

In a 2500mL two-necked flask, add 1500mL 0.2M sulfuric acid solution, 50g polyvinyl acetal foam material, 0.08mol ammonium cerium sulfate, 5mol N-isopropylacrylamide and 1.8mol methacrylamide, seal it, and react at 20°C for 55h , After the sample was taken out, it was washed with distilled water to neutrality, and dried in a vacuum oven to constant weight to obtain a polyvinyl acetal foam of graft copolymerization of poly-N-isopropylacrylamide and polymethacrylamide.

Take 0.1 g of the obtained polyvinyl alcohol-based thermosensitive macroporous material, and measure its absorption rate for distilled water at low temperature and high temperature respectively according to the method described above. At low temperature, the time to reach saturated absorption and the absorption rate are 3min and 100g/g respectively; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 3.5min and 35g/g.

Example 4

In a 2500mL two-necked flask, add 1500mL of 0.4M sulfuric acid solution, 50g of polyvinyl acetal foam material, 0.04mol of ammonium cerium sulfate, 2.25mol of N-ethylacrylamide and 2.25mol of N-methylolacrylamide, seal, and store at 30°C After reacting for 48 hours, the sample was taken out, washed with distilled water until neutral, and dried in a vacuum oven to constant weight to obtain a polyvinyl acetal foam of graft copolymerization of poly-N-ethylacrylamide and polymethylolacrylamide.

Take 0.1 g of the obtained polyvinyl alcohol-based thermosensitive macroporous material, and measure its absorption rate for distilled water at low temperature and high temperature respectively according to the method described above. At low temperature, the time to reach saturated absorption and the absorption rate are 5min and 50g/g respectively; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 3min and 24g/g, respectively.

Example 5

In a 2500mL two-necked flask, add 1500mL 0.6M sulfuric acid solution, 50g polyvinyl acetal foam material, 0.004mol cerium ammonium nitrate, 5mol N-ethylacrylamide and 1mol N-isopropylacrylamide, seal it, and react at 40°C for 36h , after the sample was taken out, it was washed with distilled water until neutral, and dried in a vacuum oven to constant weight to obtain a polyvinyl acetal foam of graft copolymerization of poly-N-ethylacrylamide and polyisopropylacrylamide.

Take 0.1 g of the obtained polyvinyl alcohol-based thermosensitive macroporous material, and measure its absorption rate for distilled water at low temperature and high temperature respectively according to the method described above. At low temperature, the time to reach saturated absorption and the absorption rate are 2.5min and 43g/g respectively; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 3min and 15g/g, respectively.

Example 6

In a 2500mL two-necked flask, add 1500mL 0.8M nitric acid solution, 50g polyvinyl acetal foam material, 0.15mol cerium ammonium nitrate, 1.2mol N-ethylacrylamide and 1mol acrylamide, seal it, react at 50°C for 24h, and take out the sample Afterwards, it is washed with distilled water to neutrality, and dried in a vacuum oven to constant weight to obtain a polyvinyl acetal foam of graft copolymerization of poly-N-ethylacrylamide and polyacrylamide.

Take 0.1 g of the obtained polyvinyl alcohol-based thermosensitive macroporous material, and measure its absorption rate for distilled water at low temperature and high temperature respectively according to the method described above. At low temperature, the time to reach saturated absorption and the absorption rate are 2.5min and 30g/g; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 2min and 14g/g, respectively.

Example 7

In a 2500mL two-necked flask, add 1500mL 1M nitric acid solution, 50g polyvinyl acetal foam material, 0.15mol cerium ammonium perchlorate, 0.7mol N-isopropylacrylamide and 0.3mol methacrylamide, seal, and store at 70°C After reacting for 24 hours, the sample was taken out, washed with distilled water until neutral, and dried in a vacuum oven to constant weight to obtain a polyvinyl acetal foam of graft copolymerization of poly-N-isopropylacrylamide and polymethacrylamide.

Take 0.1 g of the obtained polyvinyl alcohol-based thermosensitive macroporous material, and measure its absorption rate for distilled water at low temperature and high temperature respectively according to the method described above. At low temperature, the time to reach saturated absorption and the absorption rate are 2.5min and 50g/g; at high temperature, the time to reach shrinkage equilibrium and the absorption rate are 2min and 35g/g, respectively.

It can be seen from the above examples that the temperature-sensitive material prepared by the present invention has a very fast temperature response characteristic.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (9)

1. the preparation method of the macroporous polymer resin of a kind of fast temperature response, it is characterised in that comprise the following steps：

Under acid condition, in the presence of initiator, the temperature sensitive monomer of hydrophily carries out graft reaction with Pioloform, polyvinyl acetal foam, Obtain the macroporous polymer resin of fast temperature response；

The temperature sensitive monomer of hydrophily is in NIPA, N- ethyl acrylamides and N, N- acrylamide Any one or more.

2. preparation method according to claim 1, it is characterised in that the initiator is water-soluble organic and inorganic oxidation Reduction initiating system.

3. preparation method according to claim 2, it is characterised in that in the initiator, oxidant is manganese pyrophosphate, nitre Any one or a few in sour cerium ammonium, Cericammoniumsulfate and perchloric acid cerium, reducing agent is Pioloform, polyvinyl acetal foam itself.

4. preparation method according to claim 1, it is characterised in that the raw material of the graft reaction also includes hydrophily list Body, the hydrophilic monomer is any one or more in acrylamide, Methacrylamide and N hydroxymethyl acrylamide.

5. preparation method according to claim 1, it is characterised in that the graft reaction is in aqueous sulfuric acid, hydrochloric acid water Carried out in the mixed solution of any one or more in solution and phosphate aqueous solution.

6. preparation method according to claim 1, it is characterised in that the acid concentration of the acid condition is 0.01~1M.

7. preparation method according to claim 1, it is characterised in that the temperature of the graft reaction is 0~70 DEG C, reaction Time is 6~72h.

8. preparation method according to claim 1, it is characterised in that the temperature sensitive monomer of hydrophily and Pioloform, polyvinyl acetal The mol ratio of graft site is (2.5~20) in foam：1.

9. the macroporous polymer resin of fast temperature response prepared by the preparation method described in any one of claim 1~8.