#with help from

[ros-textposts]

[mizgnomer]

David Tennant Drinking  - “from glasses” edition (Part 3)

See also:  [ Part 1 ] [ Part 2 ] Drinking from Bottles [ part 1 ] [ part 2 ] [ part 3 ]

[mystical-marauder]

James: *sneezes*

Sirius: bless you

Remus: *sneezes*

Sirius: Remus, are you sick? Here let me wrap you up in a blanket- no sit down. Now would you like some soup? Tomato? Chicken? You poor thing.

Severus: *sneezes*

All the marauders: Omg shut the fuck up

[goatsmell]

Humble-Stumbling

All I can do is Be a better human Than I was yesterday

Trouble is I was pretty amazing Twenty-four hours ago

It’s going to take Some work to top That accomplishment

[materialsscienceandengineering]

Polymerization

Polymers are defined as macromolecules composed of a multitude of smaller, repeating, molecular units known as monomers. Polymers are formed when reactive monomers undergo a reaction known as polymerization. By controlling the functionality and reactivity of the monomers scientists are able to make these polymers into linear chains, branched chains, or molecular networks, the structure of which are what help give polymers their unique properties.

The mostly commonly seen types of polymerization (the general categories under which all other polymerizations tend to fall) are addition, chain-growth, condensation, and step-growth polymerization. Addition and chain-growth polymerization are often used interchangeably, as are condensation and step-growth polymerization, but this view isn’t entirely accurate. Though most step-growth polymers are also condensation polymers there are a few that are addition polymers instead. Sometimes, addition polymers that are not chain-growth polymers are said to be formed through polyaddition.

Within these types of polymerization there are numerous other methods that cannot be easily categorized. Multiple polymerization methods overlap due to the fact that they were named for different reasons.

For example, many polymerization methods are named for the mechanism involved in turning the monomer into a polymer (such as ring-opening or copper-mediated polymerization). Others are named based on the reactivity of the polymerization that occurs (such as living or reversible-deactivation polymerization) or the industrial process used in creating the polymer (such as bulk or emulsion polymerization).

Because of this overlap you can have ionic or free-radical polymerization (both types of chain-growth) that can be either living or ring-opening poylmerization (or both or neither) created through bulk polymerization. An example of a polymerization methods that defies  categorization is olefin metathesis, an organic reaction, of which two types are ring-opening metathesis polymerization (an addition, chain-growth polymerization) and acyclic diene metathesis (a condensation, step-growth polymerization).

Sources: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

Image sources: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

[hastodosomething]

it’s amazing that some of my absolute best writing is when i’m completely tearing scott apart and building him back up to something new and different. improved. but he has to be shattered and heartbroken first. 

[materialsscienceandengineering]

Chain-growth, step-growth, addition, and condensation polymerization

Chain-growth and step-growth polymerization are often considered to be the two main types of polymerization reactions, under which many other types of polymerizations - if not all - can be classified. Addition and condensation polymerization are often used interchangeably with the two (respective) processes above, but do differ slightly.

Chain-growth polymers (as opposed to step-growth) require initiators to begin the polymerization reaction. Chain-growth polymerization follows the procedure of initiation (allowing monomers to combine/attach to other monomers), propagation (in which the monomers actually attach to the initiated segment), and termination (ending the polymerization). In addition to these steps, chain-growth polymerizations can undergo a process called “chain transfer” where the reactive aspect of the growing chain (most commonly a radical, but may also occur for ionic polymerizations) is transferred to an intermediate species – such as a monomer, solvent or initiator – which terminates the growing chain and begins the growth of a new chain. Chain growth proceeds by adding one monomer at a time.

Step-growth polymers require an active functional group at each end of a monomer, such as -OH, -COOH, or -NH2. The reaction proceeds slowly, monomers reacting with each other and with the growing chains. Even when all the monomers have reacted there are still functional groups at the end of each chain, allowing the polymerization to continue. Step-growth is a slow reaction that typically requires higher temperature than chain-growth and usually results in linear chains, without branching or crosslinking. Most step-growth polymerizations create byproducts, and are thus condensation polymerizations, but a few do not.

Condensation polymers (as opposed to addition polymers) result in a byproduct (often water, sometimes other compounds such as HCl). Because these result from functional groups, all condensation polymers are step-growth polymers (though the reverse is not necessarily true).

Addition polymers react in such a way so that the final product contains all the atoms of the original monomers - each monomer is added to the next to create the polymer. Technically, there are step-growth polymers that proceed through addition polymerization, but the term is usually considered synonymous with chain-growth polymerization. The term polyaddition is sometimes used to refer to step-growth addition polymers, which proceed with independent addition reactions, as opposed to chain-growth.

Sources/Further Reading: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

Image sources: ( 1 ) ( 2 ) ( 3 )