**3.4 Polymethyl methacrylate microspheres**

The purpose of the study is to verify the behavior of bacteria with an organic microcontainers of appropriate size. The method is economical and easily manageable. Desired sphere size is about 1 μm. Polymeric methyl polymethacrylate microspheres (PMMA) were made up with radical polymerization and in particular with emulsion polymerization. The reagents we used are methyl methacrylate monomer (MMA), KPS start-up and water solvent. As the desired sphere size is approximately 1 μm, experiments were carried out changing the following parameters of the experiment: (a) the amount of solvent, (b) the amount of the authority, and (c) the amount of water. The experimental procedure was carried out in a 100 ml spherical flask, the solvent was added where, with the help of a heating plate under stirring, the temperature was maintained at 70°C. Then the monomer was added, and after 20 min stirring, the starter was added. The colloidal solution was left stirring for approximately 20 h. Polymerization took place under a nitrogen atmosphere. The following describes the puma synthesis mechanism consisting of (1) the starting stage where the authority gives free radicals and reacts with the monomer, (2) the phase of propagation is observed polymer development, and (3) the stage of termination at which two roots react with each other, and the polymerization is terminated by taking PMMA as a product. **Figure 9** summarizes the procedure (**Table 4**).

**Table 5** gives the quantities of reagents that led to PMMA microsphere synthesis with the largest size, in each of a series of experiments.

**Figure 10** shows the size of the microcontainers as a function of water (A), MMA (B), and C starter.

According to the above diagrams, it is observed that the largest size of PMMA microbeads synthesized results from the second series of experiments, i.e., by changing the amount of monomer by keeping the remaining parameters of the experiment constant. **Figure 11** shows the micrograph of the samples by SEM.

The SEM image above shows the size of the PMMA micro-containers with the largest diameter achieved. As observed from the above image, the sample shows a large multi-dispersion. The characterization of the size of PMMA micro-containers was subsequently made with the dynamic scattering of light. As described in the

*Self-Healing of Concrete through Ceramic Nanocontainers Loaded with Corrosion Inhibitors… DOI: http://dx.doi.org/10.5772/intechopen.93514*

### **Figure 9.**

*PMMA microcontainer synthesis mechanism.*


### **Table 4.**

*The size of microspheres resulting from both series of experiments.*


### **Table 5.**

*Quantities of reagents in each series of experiments with the corresponding size resulting each time.*

case of SiO2 micro-containers, a study was carried out to find the optimal sample concentration for the appropriate measurement of DLS. In this case, it was found that the optimal concentration is 10 mg/L. The following diagram, in addition to the size of the micro-containers resulting from the measurement, also lists the z-potential of the sample. This studies whether or not the suspension is stable. According to the DLS measurement, the resulting PMMA size is 780 ± 25 nm, which is in line with the SEM measurement. The ζ-potential is −38.6 ± 0.651, which attests to the stability of the samples. PMMA microsphere synthesis is economical, easily manageable and takes place in aqueous environment. For the production of a product, in industry, the above factors are very important.

### **3.5 Microcontainers with polyurea shell**

The ultimate purpose of this study is to trap the bacteria spores in the microcontainers with polyurea shells. This can be done if the spores of the microorganism are scattered in the drops of the oily phase, and the shell forms around them.

*(A) PMMA microsphere size changing the amount of solvent, (B) PMMA microsphere size changing the amount of monomer, and (C) PMMA microsphere size changing the amount of the beginning.*

**Figure 11.** *SEM image of the PMMA micro-container with a size of 711 ± 90 nm.*

The synthesis of polyurethane-coated microcontainers is achieved through interfacial polymerization (IP) in an oil emulsion in water (O/W emulsion). The synthesis of polyurea shell micro-containers is achieved by polymerization on the middle surface of two liquids that are not mixed together. This study investigated an oil emulsion in water (O/W emulsion). The reagents used are organic soluble monomer (toluene diisocyanate [TDI]), water-soluble monomer (ethylenediamine, EDA, diethylenediamine, DETA), ethylenediamine (EDA), oil phase (1-octadecene, paraffin), water phase (H2O), emulsifier (sodium sulphonate dodecyl, SDS), methyl ester poly ethylene glycol (PEG), polyvinylpyrrolidone (PVP), Triton x-100, catalyst (NH4Cl) and solvent (acetone). Four series of experiments were carried out by changing some parameters, keeping the remaining constants, in order to synthesize

### *Self-Healing of Concrete through Ceramic Nanocontainers Loaded with Corrosion Inhibitors… DOI: http://dx.doi.org/10.5772/intechopen.93514*

polyuria shell containers. The experimental procedure followed in all four series of experiments is as follows: For the composition of the oily solution in a boiling glass, mix the organic soluble monomer with the organic phase and acetone. The stirring lasts a few minutes. The oil emulsion in water is formed when the oil solution is added to 50 ml of aqueous solution containing 5% w/w emulsifier. Stirring of the system takes place at ambient temperature and at 300 rpm/min for 5 min. The watersoluble monomer solution in the emulsion is added drip and stirring at 600 rpm. Then add 5% w/w NH4Cl and stir continuously for 3 h at 60°C. Finally, the sediment is centrifuged, washed with 30% ETOH, and left for drying [4]. In the first series of experiments, the possibility of forming polyurea shell micro-containers using two different water-soluble monomers (EDA and DETA) with an emulsifier SDS is studied. All other factors in the experiment remain the same. In the second series of experiments, the possibility of different emulsifiers (SDS, PEG, PVP, and Triton x-100) for the formation of polyuria shell micro pots is studied, using DETA as a water-soluble monomer. All other factors in the experiment remain the same. The third series of experiments studies the action of different phases of oil (1-Decaoctene and paraffin) using Triton x-100 as an emulsifier and as a water-soluble monomer DETA. All other factors in the experiment remain the same. The fourth series of experiments studies the dependence of the composition of micro pots on the quantity of peg emulsifier. Paraffin was used as an oily phase and DETA was used as a water-soluble monomer. All other factors in the experiment remain the same. **Figure 12** shows the synthesis of micro-containers of polyurea with different amines.

The mixture of the oil phase, containing the oil and TDI, is dispersed in the aqueous phase with the emulsifier, thus forming an oil emulsion in/water (O/W emulsion). Initially, in the aqueous phase, the hydrophobic groups of the emulsifier are covered by its hydrophilic groups, in such a way that micelles are formed (**Figure 10**). Adding the oil solution, the hydrophilic groups are diffused into

**Figure 12.** *Representation of the composition of polyurea micro-containers with different amines.*

### *Advanced Ceramic Materials*

the oil, while the hydrophilic along the drop covering it. The formation of the shell begins when regional isocyanate groups of TDI are hydrolyzed in the oil-water middle surface forming amines, according to the reaction:

$$\text{RNCO} + \text{H}\_2\text{O} \rightarrow \text{RNH}\_2 + \text{CO}\_2 \tag{1}$$

These amines react with non-hydrolyzed isocyanate groups, thereby forming a polyuria network. When the original shell is formed, the added amine (the watersoluble monomer) must penetrate the membrane and penetrate the oil phase to react with TDI (the organ soluble monomer). This makes the polyurea shell denser and more durable. As a result, the formation of a polymer shell (consisting of a polyuria network) is observed on the interface of the emulsifier and the oil phase, due to the reaction between amine and TDI. The temperature that the reaction takes place is the ambient temperature [4]. The series of experiments on the composition of polyuria shell micro-containers were carried out in order to find the most suitable experimental conditions for an efficient result. Thus, the experiments are related to each other by following each time the most promising result. Thus, in the first series SDS is used as an emulsifier and EDA and DETA are used as amines. Between the two amines, the other studies used DETA, as it showed the best micro-pot formation. The second study showed that PEG and Triton x lead to the formation of micro-containers. Below is the SEM image of the sample where DETA has been used as an amine while PEG has been used as an emulsifier. **Figure 13** shows SEM of the sample of polyurea shell containers from the second series of experiments, emulsifier PEG.

As well, the study of specific microcontainers is indicative that an average microsphere size has not been found as in all previous microsphere studies. The above image is not representative for the entire sample. An indicative study of the composition of microspheres with polyuria shell was carried out in this section. Polyuria has very good strength and is insoluble in most solvents. That is why it was chosen to study such a system. Experiments were conducted changing parameters of the experiment. Promising results give those cases where PEG and Triton x with amine DETA are used as emulsifiers and as an oil phase 1-octadecene.

### **Figure 13.**

*SEM image of the sample of polyurea shell micro-containers from the second series of experiments, emulsifier PEG.*

*Self-Healing of Concrete through Ceramic Nanocontainers Loaded with Corrosion Inhibitors… DOI: http://dx.doi.org/10.5772/intechopen.93514*
