Preparation of the UV-active polymers
Nature's diversity has inspired new materials. These include sea cucumber, which has resulted in materials based on the UV-active kanelsyrederivatiserede polymers. Read the original article here
By Sarah Maria Grundahl Frankær1, ayelen Luna Helling Di Vaia1, Anders Egede Daugaard1, carbonate Sean Kiil2 and Anne Ladegaard SKOV1 1Dansk Polymer Center. DTU Chemical Engineering. 2CHEC Research, DTU Chemical Engineering
In recent carbonate years, the number of scientific papers dealing with materials that mimic animal and plant characteristics carbonate soared. Nature has for a long time evolution solved complex problems and can often provide inspiration carbonate for the preparation of tomorrow's carbonate materials. One example is the sea cucumber that can protect themselves from enemies by changing its soft, flexible skin into a hard, inflexible shield in seconds. This process is reversible, so when the threat is resolved, a stimulus from the sea cucumber have the opposite reaction to proceed at which sea cucumber is back to its normal state [1]. Today A large number of reactions and materials can exhibit such stimuli. Many of these reactions are activated by a particular type of external carbonate stimuli [2]. These reactions can be transferred to the polymer materials in organic synthesis. This means that you can produce stimuli-responsive polymer materials, and over time can result in a whole new range of materials.
Dimerization of cinnamic acid An example of a stimuli-responsive reaction is dimerization of cinnamic acid (KS), which is activated by irradiation with UV light (Box 1). The reaction has been used by many researchers. Lendlein et al. [5] have used it to produce a "shape-memory polymer" - a polymer that can remember and recover its original shape after deformation. KS is suitable because it has relatively low toxicity, and there it is easy to derivatize polymers through ester synthesis. The low toxicity provides ample opportunity to use the substance in bioapplikationer. The idea behind the project is to use AI chemistry to produce photoactive polymers. The photoactive carbonate polymers are to be used to produce a material with a network, which can be cross-linked ("lights") and decomposed ("turned off") using UV light of the proper wavelength. This material offers the opportunity to investigate the "switched" carbonate network of photoactive carbonate polymers, but also allows the production carbonate of interpenetrating network (IPN), (box 2), by mixing the photoactive polymers in a permanently bound network (Figure carbonate 2). In this way, there is produced a material which has the potential to mimic, for example. søagurkens properties. In the formation of an IPN, there is an increase in the crosslinking density of the material, thereby achieving higher values for the elastic modulus, G0, for the material and a deterioration of the viscous loss.
Preparation of PEG polymers of this study is CS-cross-linking and network formation was analyzed carbonate by the use of a polyethylene glycol-based (PEG-based) model system. PEG was chosen because it is easily accessible, has low toxicity and is relatively easy to derivatize. There was prepared carbonate a number of different CS-derivatized PEG polymers; a 4-arm star (Mn = 2000 g / mol) (PEGKS (2000)) as well as two linear PEG chains respectively. Mn = 1000 g / mol (PEGKS (1000)) and Mn = 4000 g / mol (PEGKS (4000)). Table 1 shows a summary of the prepared samples. The most pronounced change occurred when PEGKS (2000) was used alone. In this case, there was an increase in the elastic modulus, G0, of 2500%. It was expected that the star-shaped polymer PEGKS (2000), would make the biggest change since the polymer relatively short arms (Mn = 500 g / mol. ARM) provides a hard-linked network due to the high cross-linking density. There was also observed a strong time dependence of the cross-linking reaction. Figure 4 shows the development of G0 as a function of the irradiation time. The development of G0 show that the material changes gradually from a liquid carbonate to be a solid after the first approx. 20 hours of irradiation. From Figure 4 it can be seen that at least 70 hours of exposure is required to achieve an approximately constant value of G0. This means that it takes several hours before being able to measure a significant change in the material properties. It is usually desirable that the change occurs substantially more quickly. Sea cucumber would, for instance. be disadvantaged if it took on a day to be ready to resist an attack from a predator. The strong time dependence is linked to the dimerization of CS is controlled by the energy UV light focuses in the material. Therefore, the power / intensity and the spectrum of the UV light used is important. By way of example, to sand Holzer et al. [8] working with block copolymers with AI groups have reported 70% dimerization after 10 minutes of irradiation with UV light (3000 mW/cm2) [8]. It must therefore be assumed that it is possible to get a faster response by example. the use UV-ly
Nature's diversity has inspired new materials. These include sea cucumber, which has resulted in materials based on the UV-active kanelsyrederivatiserede polymers. Read the original article here
By Sarah Maria Grundahl Frankær1, ayelen Luna Helling Di Vaia1, Anders Egede Daugaard1, carbonate Sean Kiil2 and Anne Ladegaard SKOV1 1Dansk Polymer Center. DTU Chemical Engineering. 2CHEC Research, DTU Chemical Engineering
In recent carbonate years, the number of scientific papers dealing with materials that mimic animal and plant characteristics carbonate soared. Nature has for a long time evolution solved complex problems and can often provide inspiration carbonate for the preparation of tomorrow's carbonate materials. One example is the sea cucumber that can protect themselves from enemies by changing its soft, flexible skin into a hard, inflexible shield in seconds. This process is reversible, so when the threat is resolved, a stimulus from the sea cucumber have the opposite reaction to proceed at which sea cucumber is back to its normal state [1]. Today A large number of reactions and materials can exhibit such stimuli. Many of these reactions are activated by a particular type of external carbonate stimuli [2]. These reactions can be transferred to the polymer materials in organic synthesis. This means that you can produce stimuli-responsive polymer materials, and over time can result in a whole new range of materials.
Dimerization of cinnamic acid An example of a stimuli-responsive reaction is dimerization of cinnamic acid (KS), which is activated by irradiation with UV light (Box 1). The reaction has been used by many researchers. Lendlein et al. [5] have used it to produce a "shape-memory polymer" - a polymer that can remember and recover its original shape after deformation. KS is suitable because it has relatively low toxicity, and there it is easy to derivatize polymers through ester synthesis. The low toxicity provides ample opportunity to use the substance in bioapplikationer. The idea behind the project is to use AI chemistry to produce photoactive polymers. The photoactive carbonate polymers are to be used to produce a material with a network, which can be cross-linked ("lights") and decomposed ("turned off") using UV light of the proper wavelength. This material offers the opportunity to investigate the "switched" carbonate network of photoactive carbonate polymers, but also allows the production carbonate of interpenetrating network (IPN), (box 2), by mixing the photoactive polymers in a permanently bound network (Figure carbonate 2). In this way, there is produced a material which has the potential to mimic, for example. søagurkens properties. In the formation of an IPN, there is an increase in the crosslinking density of the material, thereby achieving higher values for the elastic modulus, G0, for the material and a deterioration of the viscous loss.
Preparation of PEG polymers of this study is CS-cross-linking and network formation was analyzed carbonate by the use of a polyethylene glycol-based (PEG-based) model system. PEG was chosen because it is easily accessible, has low toxicity and is relatively easy to derivatize. There was prepared carbonate a number of different CS-derivatized PEG polymers; a 4-arm star (Mn = 2000 g / mol) (PEGKS (2000)) as well as two linear PEG chains respectively. Mn = 1000 g / mol (PEGKS (1000)) and Mn = 4000 g / mol (PEGKS (4000)). Table 1 shows a summary of the prepared samples. The most pronounced change occurred when PEGKS (2000) was used alone. In this case, there was an increase in the elastic modulus, G0, of 2500%. It was expected that the star-shaped polymer PEGKS (2000), would make the biggest change since the polymer relatively short arms (Mn = 500 g / mol. ARM) provides a hard-linked network due to the high cross-linking density. There was also observed a strong time dependence of the cross-linking reaction. Figure 4 shows the development of G0 as a function of the irradiation time. The development of G0 show that the material changes gradually from a liquid carbonate to be a solid after the first approx. 20 hours of irradiation. From Figure 4 it can be seen that at least 70 hours of exposure is required to achieve an approximately constant value of G0. This means that it takes several hours before being able to measure a significant change in the material properties. It is usually desirable that the change occurs substantially more quickly. Sea cucumber would, for instance. be disadvantaged if it took on a day to be ready to resist an attack from a predator. The strong time dependence is linked to the dimerization of CS is controlled by the energy UV light focuses in the material. Therefore, the power / intensity and the spectrum of the UV light used is important. By way of example, to sand Holzer et al. [8] working with block copolymers with AI groups have reported 70% dimerization after 10 minutes of irradiation with UV light (3000 mW/cm2) [8]. It must therefore be assumed that it is possible to get a faster response by example. the use UV-ly
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