Part 1: Material Science & Engineering

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Properties of materials, classes of materials used in medicine,... As the main contents of the document "Part 1: Material Science & Engineering". Invite you to consult the text book for more documents serving the academic needs and research.

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Nội dung Text: Part 1: Material Science & Engineering

Part 1: Material Science & Engineering Chap. 1. Properties of materials - The structure of solids - Mechanical properties of materials - Surface properties of materials - Role of water in biomaterials Chap. 2. Classes of materials used in medicine - Polymer - Silicone - Medical fibers & biotextiles - Hydrogels - Applications of “Smart Polymers” as biomaterials - Bioresorbable and bioerodible materials 1 Advanced Program Biomedical Engineering – HUST, Vietnam Part 1: Material Science & Engineering Chap. 2.(cont.) - Natural materials - Metals - Ceramics, glasses, and glass-ceramics - Composite - Nonfouling (Anti-fouling) surfaces - Surface modification of materials used in medicine - Textured and porous materials - Surface-immobilized Biomolecules 2 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer Chapter 2 Classes of materials used in medicine 3 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer Classes of biomaterials -Polymers -Metals -Ceramics -Natural materials 1. What is polymer? -Long-chain, consists of many repeating units (monomeric monomeric units) units -Small molecule (repeating units) link together by primary covalent bonding - Monomer: Monomer initial substance to form polymer (ethylene, methyl methacrylate, amide…) - n (number of repeating units, degree of polymerization): polymerization over 1,000 to form strong solids . Small n: oligomer (M about 500- 6,000) . Great n: high polymer (104-106) Mer and chain structure of (a) polytetraflouroethylene; (b) polyvinylchloride; (c) polypropylene 4 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer Polyethylene: (a) mer and chain structure; (b) Zigzac backbone structure of molecule 5 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer - The main backbone chain (polymeric polymeric chain) chain can be made up of different atoms such as silicone rubber-SR or same atoms such as polyethylene-PE - Homopolymer: Homopolymer polymer containing one type of repeating units (PMMA, SR, PVC, PE) - Copolymer: Copolymer two or more type of repeating units (styrene-butadiene rubber, polylactide polyglycolic acid - Very different from molecule structure - Can be synthetic (PE,PP, PMMA) or natural (cellulose, natural rubber, collagen, DNA…) - Wide range of characteristics (biodegradable or not, hydrophilic or hydrophobic, non- water absorbing or water swelling, saturated or not saturated) - Properties depend on chemical structure, geological structure, polymerization degree (molecular weight - Classification: thermoplastics, thermosetting, elastomer 2. Nomenclature of polymer - Usually: adding prefix poly to name of monomer (ethylene- polyethylene; methyl methacrylate- polymethyl-methacrylate) - Name of monomers (phenol and formaldehyde- phenolformadehyde 6 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer 3. Molecular weight (size) Average molecular weight Mn: Number average molecular weight Mw: Weight average molecular weight Ni: number of mole of species I Mi: molecular weight of species I Molecular weight distribution PI: Mw/Mn: Polydispersity index (indicates the breadth of molecular weight distribution -Average molecular weight is very important for mechanical properties, adsorption and processing -Molecular weight distribution shows the homogenity of the properties 7 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 3. Synthesis (Polymerization) 3.1. Addition polymerization (chain reaction) - Simple addition of monomer molecules to each other - Without the lost of any atoms (no side products) - Monomers should contain un-saturated bonding such as double bonds, triple bonds, dien (ethylene, acetylene, butadiene…) - Initiators (can be free radicals, cations, anions or stereospecific catalyst) :usually needed to open double bonds to cause activate site - Polymerization mechanism: initiation (form activated site for reaction), propagation (additional reaction for rapid chain growth) and termination - Can result in homo-polymer or copolymer - Examples: PE, PP, PMMA, PVC 3.2. Condensation polymerization (stepwise growth) - Two different monomers react to from a covalent bond - Usually produces small molecules condensed out as side products (water, salt, HCl…) - Examples: polyester, polyamide, polysiloxane, poly(ethylene terephtalate) 8 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer Example for polymerization 9 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer Example for polymerization 10 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer Example for polymerization 11 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 4. Molecule structure 4.1. Polymer structure (a): Linear (b) (b): Branched (a) (c): Crosslinked (d): Netwok (three- dimensional) (c) (d) 12 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer 4.2. Molecule structure of copolymer (a): Random (a) (b): Alternating (c): Block (d): Graft (b) (c) (d) 13 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 4.4. Polymer chain arrangement 14 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer 5. Configuration (Tacticity or Stereoisomerism) (For linear and branched polymer) - Tacticity refers to the arrangement of substituent groups around extended polymer chain - Atactic configuration: substituent groups at random on other side of extended chain backbone; can not crystalize (amorphous polymer) - Syndiotactic: Syndiotactic substituents alternating from side to side of the backbone, may crystallize - Isotactic: Isotactic substituents located on the same side of the zigzac plane of chain backbone, may crystallize 15 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer Relationship Structure- Characteristics 16 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer 7. Important polymeric implant materials 17 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 7.1. Polyamide (Nylons) -Polymerize by step-reaction & ring-scission -Have interchain hydrogen bonding and high degree of crystallinity, lead to excellent fiber-forming ability, used for surgical sutures - Basic chemical structure repeating units: different, lead to very different polyamides - Nylons are hydroscopic & lose their strength in vivo when implanted (water molecules serve as plasticizers - Proteolytic enzymes also attack amides groups 17 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer Basic chemical structure of PA from diamine + diacidsNylon ; Nylon type 66 or 610 Nylon type 6 Aromatic polyamides, named Aramide 5 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 7.2. Polyethylene - Can crystallize - Can polymerized at high pressure with radical catalyst (low density PE), or at low pressure with Ziegler catalyst (high-density PE- not contain branches) - Crystallinity: very vary - can be used in solid or porous form - HDPE: used as tubing for drains and catheters - Ultra-molecular weight PE (UHMWPE): extensively used in orthopedic implant fabrications (joint implants) - Biocompatibility: poor 7.2. Polypropylene -Usually crystallize (except atactic) - Have exceptional high flexural fatigue life, used to make intergrally molded hinges for finger joint prostheses -Have excellent environmental stress-cracking resistance, used for sutures and hernia repair 8 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer 8 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 8 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.2. Classes of materials used in medicine- Polymer 7.3. Polyacrylates -Have excellent physical and coloring properties, easy to fabricate -Extensively used for detal cement (polyacrylic acid), hard contact lenses, bone cement * Polymethyl metacrylate (PMMA) -Hydrophobic, amorphous, transparent, glassy at room temperature, tough, stable, excellent light transmittance -Used as major ingredient for bone cement, good for intraocular and hard contact lenses •Poly HEMA: soft contact lenses 7.4.PVC -Tubing (blood transfusion, feeding, dialysis) and blood storage bags -Plasticizer problem 7.5 PDMS or SR. -For finger joint, hart valves, breath implant, for chin, ear, nose reconstruction -Oxygenator membranes 7.6. PEG: drug delivery, modify polymer surface to form non-fouling surface 8 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.2. Classes of materials used in medicine- Polymer 8 Advanced Program Biomedical Engineering – HUST, Vietnam