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PH-sensitive polymers AI simulator
(@PH-sensitive polymers_simulator)
Hub AI
PH-sensitive polymers AI simulator
(@PH-sensitive polymers_simulator)
PH-sensitive polymers
pH sensitive or pH responsive polymers are materials which will respond to the changes in the pH of the surrounding medium by varying their dimensions. Materials may swell, collapse, or change depending on the pH of their environment. This behavior is exhibited due to the presence of certain functional groups in the polymer chain. pH-sensitive materials can be either acidic or basic, responding to either basic or acidic pH values. These polymers can be designed with many different architectures for different applications. Key uses of pH sensitive polymers are controlled drug delivery systems, biomimetics, micromechanical systems, separation processes, and surface functionalization.
pH sensitive polymers can be broken into two categories: those with acidic groups (such as -COOH and -SO3H) and those with basic groups (-NH2). The mechanism of response is the same for both, only the stimulus varies. The general form of the polymer is a backbone with functional "pendant groups" that hang off of it. When these functional groups become ionized in certain pH levels, they acquire a charge (+/-). Repulsions between like charges cause the polymers to change shape.
Polyacids, also known as anionic polymers, are polymers that have acidic groups. Examples of acidic functional groups include carboxylic acids (-COOH), sulfonic acids (-SO3H), phosphonic acids, and boronic acids. Polyacids accept protons at low pH values. At higher pH values, they deprotonate and become negatively charged. The negative charges create a repulsion that causes the polymer to swell. This swelling behavior is observed when the pH is greater than the pKa of the polymer. Examples include polymethyl methacrylate polymers (pharmacologyonline 1 (2011)152-164) and cellulose acetate phthalate.
Polybases are the basic equivalent of polyacids and are also known as cationic polymers. They accept protons at low pH like polyacids do, but they then become positively charged. In contrast, at higher pH values they are neutral. Swelling behavior is seen when the pH is less than the pKa of the polymer.
Although many sources talk about synthetic pH sensitive polymers, natural polymers can also display pH-responsive behavior. Examples include chitosan, hyaluronic acid, alginic acid and dextran. Chitosan, a frequently used example, is cationic. Since DNA is negatively charged, DNA could be attached to chitosan as a way to deliver genes to cells. Alginic acid, on the other hand, is anionic. It is often evaluated as a calcium-salt for drug delivery applications(International journal of biological macromolecules 75 (2015) 409-17) . Natural polymers have appeal because they display good biocompatibility, which makes them useful for biomedical applications. However, a disadvantage to natural polymers is that researchers can have more control over the structure of synthetic polymers and so can design those polymers for specific applications.
Polymers can be designed to respond to more than one external stimulus, such as pH and temperature. Often, these polymers are structured as a copolymer where each polymer displays one type of response.
pH sensitive polymers have been created with linear block copolymer, star, branched, dendrimer, brush, and comb architectures. Polymers of different architectures will self-assemble into different structures. This self-assembly can occur due to the nature of the polymer and the solvent, or due to a change in pH. pH changes can also cause the larger structure to swell or deswell. For example, block copolymers often form micelles, as will star polymers and branched polymers. However, star and branched polymers can form rod or worm-shaped micelles rather than the typical spheres. Brush polymers are usually used for modifying surfaces since their structure doesn’t allow them to form a larger structure like a micelle.
Often, the response to different pH values is swelling or deswelling. For example, polyacids release protons to become negatively charged at high pH. Since polymer chains are often in close proximity to other parts of the same chain or to other chains, like-charged parts of the polymer repel each other. This repulsion leads to a swelling of the polymer.[citation needed]
PH-sensitive polymers
pH sensitive or pH responsive polymers are materials which will respond to the changes in the pH of the surrounding medium by varying their dimensions. Materials may swell, collapse, or change depending on the pH of their environment. This behavior is exhibited due to the presence of certain functional groups in the polymer chain. pH-sensitive materials can be either acidic or basic, responding to either basic or acidic pH values. These polymers can be designed with many different architectures for different applications. Key uses of pH sensitive polymers are controlled drug delivery systems, biomimetics, micromechanical systems, separation processes, and surface functionalization.
pH sensitive polymers can be broken into two categories: those with acidic groups (such as -COOH and -SO3H) and those with basic groups (-NH2). The mechanism of response is the same for both, only the stimulus varies. The general form of the polymer is a backbone with functional "pendant groups" that hang off of it. When these functional groups become ionized in certain pH levels, they acquire a charge (+/-). Repulsions between like charges cause the polymers to change shape.
Polyacids, also known as anionic polymers, are polymers that have acidic groups. Examples of acidic functional groups include carboxylic acids (-COOH), sulfonic acids (-SO3H), phosphonic acids, and boronic acids. Polyacids accept protons at low pH values. At higher pH values, they deprotonate and become negatively charged. The negative charges create a repulsion that causes the polymer to swell. This swelling behavior is observed when the pH is greater than the pKa of the polymer. Examples include polymethyl methacrylate polymers (pharmacologyonline 1 (2011)152-164) and cellulose acetate phthalate.
Polybases are the basic equivalent of polyacids and are also known as cationic polymers. They accept protons at low pH like polyacids do, but they then become positively charged. In contrast, at higher pH values they are neutral. Swelling behavior is seen when the pH is less than the pKa of the polymer.
Although many sources talk about synthetic pH sensitive polymers, natural polymers can also display pH-responsive behavior. Examples include chitosan, hyaluronic acid, alginic acid and dextran. Chitosan, a frequently used example, is cationic. Since DNA is negatively charged, DNA could be attached to chitosan as a way to deliver genes to cells. Alginic acid, on the other hand, is anionic. It is often evaluated as a calcium-salt for drug delivery applications(International journal of biological macromolecules 75 (2015) 409-17) . Natural polymers have appeal because they display good biocompatibility, which makes them useful for biomedical applications. However, a disadvantage to natural polymers is that researchers can have more control over the structure of synthetic polymers and so can design those polymers for specific applications.
Polymers can be designed to respond to more than one external stimulus, such as pH and temperature. Often, these polymers are structured as a copolymer where each polymer displays one type of response.
pH sensitive polymers have been created with linear block copolymer, star, branched, dendrimer, brush, and comb architectures. Polymers of different architectures will self-assemble into different structures. This self-assembly can occur due to the nature of the polymer and the solvent, or due to a change in pH. pH changes can also cause the larger structure to swell or deswell. For example, block copolymers often form micelles, as will star polymers and branched polymers. However, star and branched polymers can form rod or worm-shaped micelles rather than the typical spheres. Brush polymers are usually used for modifying surfaces since their structure doesn’t allow them to form a larger structure like a micelle.
Often, the response to different pH values is swelling or deswelling. For example, polyacids release protons to become negatively charged at high pH. Since polymer chains are often in close proximity to other parts of the same chain or to other chains, like-charged parts of the polymer repel each other. This repulsion leads to a swelling of the polymer.[citation needed]